simple load balancing with iptables

iptables has an extension called clusterip. Clusterip extension uses multicast arp feature to achieve load balancing. Let's say we have two web servers called web1(192.168.0.1) and web2(192.168.0.2) and a virtual ip (192.168.0.10) which will be accepting requests for these machines.

virtual ip:192.168.0.10
web1:192.168.0.1
web2:192.168.0.2

Virtual ip will accept the requests and load balance them between these two web servers.

on web1 server run:

# iptables -I INPUT -d 192.168.0.10 -i eth0 -p tcp --dport 80 -j CLUSTERIP --new --clustermac 01:02:03:04:05:06 --total-nodes 2 --local-node 1 --hashmode sourceip
# ifconfig eth0:1 192.168.0.10 netmask 255.255.255.0 up

on web2 server run:
# iptables -I INPUT -d 192.168.0.10 -i eth0 -p tcp --dport 80 -j CLUSTERIP --new --clustermac 01:02:03:04:05:06 --total-nodes 2 --local-node 2 --hashmode sourceip
# ifconfig eth0:1 192.168.0.10 netmask 255.255.255.0 up

only difference between web1 and web2 commands is local-node option as seen above.
now any web requests coming to 192.168.0.10 will be load balanced between web1 and web2.

clusterip supports three hashmodes (sourceip,sourceip-sourceport and sourceip-sourceport-destport) to determine how to route requests to each servers.

This configuration has one drawback. If one of the nodes fall, the other one does not serves incoming requests for the other one. You need to install linux-ha.

If you want to see which requests served by web1 for example, simply run
# cat /proc/net/ipt_CLUSTERIP/192.168.0.1

Let's say web2 is crashed and we would like to first web server (web1) to take care the requests coming to web2.
on web1 server run:
# echo "+2" >> /proc/net/ipt_CLUSTERIP/192.168.0.1
now on, web1 will take the requests coming to web1.
When you up the web2 server, just run
# echo "-2" >> /proc/net/ipt_CLUSTERIP/192.168.0.1
and web1 will not serve the request for web2.

How to prevent from DDOS

How to prevent from DDoS Attacks:-
Implement security features in your server like:
1) DDOS protection using CSF through “SYNFLOOD”.
2) Install apache modules like mod_dosevasive and mod_security in your server.
3) The best,free & open sources solution to protect from DDOs :- http://deflate.medialayer.com/
4) Configure APF and IPTABLES to reduce the DDOS.
===========================================
Description here :-
1.) DDOS protection using CSF through “SYNFLOOD”. & Connection tracking :- Please modify these option through CSF
:-
# Enable SYN Flood Protection. This option configures iptables to offer some
# protection from tcp SYN packet DOS attempts. You should set the RATE so that
# false-positives are kept to a minimum otherwise visitors may see connection
# issues (check /var/log/messages for *SYNFLOOD Blocked*). See the iptables
# man page for the correct –limit rate syntax
SYNFLOOD = Default: 0
SYNFLOOD_RATE = 100/s
SYNFLOOD_BURST = 150
# Connection Tracking. This option enables tracking of all connections from IP
# addresses to the server. If the total number of connections is greater than
# this value then the offending IP address is blocked. This can be used to help
# prevent some types of DOS attack.
#
# Care should be taken with this option. It’s entirely possible that you will
# see false-positives. Some protocols can be connection hungry, e.g. FTP, IMAPD
# and HTTP so it could be quite easy to trigger, especially with a lot of
# closed connections in TIME_WAIT. However, for a server that is prone to DOS
# attacks this may be very useful. A reasonable setting for this option might
# be arround 300.
#
# To disable this feature, set this to 0
CT_LIMIT = Default: 50 (means 50 connections per ip address)
# Connection Tracking interval. Set this to the the number of seconds between
# connection tracking scans
CT_INTERVAL = Default: 30
# Send an email alert if an IP address is blocked due to connection tracking
CT_EMAIL_ALERT = Default: 1
# If you want to make IP blocks permanent then set this to 1, otherwise blocks
# will be temporary and will be cleared after CT_BLOCK_TIME seconds
CT_PERMANENT = Default: 0
# If you opt for temporary IP blocks for CT, then the following is the interval
# in seconds that the IP will remained blocked for (e.g. 1800 = 30 mins)
CT_BLOCK_TIME = Default: 1800
# If you don’t want to count the TIME_WAIT state against the connection count
# then set the following to “1″
CT_SKIP_TIME_WAIT = Default: 0
# If you only want to count specific states (e.g. SYN_RECV) then add the states
# to the following as a comma separated list. E.g. “SYN_RECV,TIME_WAIT”
#
# Leave this option empty to count all states against CT_LIMIT
CT_STATES =
# If you only want to count specific ports (e.g. 80,443) then add the ports
# to the following as a comma separated list. E.g. “80,443″
#
# Leave this option empty to count all ports against CT_LIMIT
CT_PORTS = 80,443
==================================================== 
2) Install apache modules like mod_dosevasive and mod_security in your server= :-
mod_evasive and mod_security modules are used to secure Apache Web Server from DDoS and brute force attacks by implementing web application firewall.
The mod_evasive authoring site (zdziarski.com) states that mod_evasive is an evasive maneuvers module for Apache to provide evasive action in the event of an HTTP DoS or DDoS attack or brute force attack. It is also designed to be a detection and network management tool, and can be easily configured to talk to ipchains, firewalls, routers, and etcetera..
*Note: mod_evasive module has been known to cause problems with frontpage server extensions. If you use frontpage server extension, you should thoroughly test your mod_evasive installation before deploying a production server.
# wget http://www.zdziarski.com/blog/wp-content/uploads/2010/02/mod_evasive_1.10.1.tar.gz
#tar -xvzf mod_evasive_1.10.1.tar.gz
# cd mod_evasive
# /usr/local/apache/bin/apxs -cia mod_evasive.c
# mv mod_evasive.loT mod_evasive.lo
# /usr/local/apache/bin/apxs -cia mod_evasive.c
# httpd -M|grep evasiv
# vi /etc/httpd/conf/httpd.conf (edit httpd.conf with the following details)

DOSHashTableSize   3097
DOSPageCount   2
DOSSiteCount   50
DOSPageInterval   1
DOSSiteInterval   1
DOSBlockingPeriod   600

# cd /usr/local/apache/modules/
Then download mod_evasive20.so through web and place it in modules directory and change the permission with 755.
# /etc/init.d/httpd restart
==================================================================================
3) The best,free & open sources solution to protect from DDOs :- http://deflate.medialayer.com/ :-
(D)DoS Deflate is a lightweight bash shell script designed to assist in the process of blocking a denial of service attack. It utilizes the command below to create a list of IP addresses connected to the server, along with their total number of connections. It is one of the simplest and easiest to install solutions at the software level.
netstat -ntu | awk ‘{print $5}’ | cut -d: -f1 | sort | uniq -c | sort -n
IP addresses with over a pre-configured number of connections are automatically blocked in the server’s firewall, which can be direct iptables or Advanced Policy Firewall (APF). (We highly recommend that you use APF on your server in general, but deflate will work without it.)
Notable Features :-
* It is possible to whitelist IP addresses, via /usr/local/ddos/ignore.ip.list.
* Simple configuration file: /usr/local/ddos/ddos.conf
* IP addresses are automatically unblocked after a preconfigured time limit (default: 600 seconds)
* The script can run at a chosen frequency via the configuration file (default: 1 minute)
* You can receive email alerts when IP addresses are blocked.
Installation :-
wget http://www.inetbase.com/scripts/ddos/install.sh
chmod 0700 install.sh
./install.sh
Uninstallation :-
wget http://www.inetbase.com/scripts/ddos/uninstall.ddos
chmod 0700 uninstall.ddos
./uninstall.ddos
===================================================================
4) Configure APF and IPTABLES to reduce the DDOS. :-
Ans :- Please install APF/CSF or iptables to reduce the DDOS ,also an hardware firewall (cisco guard ) also help to mitigate DDOS attacks.

Iptables Limits Connections Per IP

How do I restrict the number of connections used by a single IP address to my server for port 80 and 25 using iptables?

Syntax

The syntax is as follows:

/sbin/iptables -A INPUT -p tcp --syn --dport $port -m connlimit --connlimit-above N -j REJECT --reject-with tcp-reset
# save the changes see iptables-save man page, the following is redhat and friends specific command
service iptables save

Example: Limit SSH Connections Per IP / Host

Only allow 3 ssh connections per client host:

/sbin/iptables  -A INPUT -p tcp --syn --dport 22 -m connlimit --connlimit-above 3 -j REJECT
# save the changes see iptables-save man page, the following is redhat and friends specific command
service iptables save

Example: Limit HTTP Connections Per IP / Host

Only allow 20 http connections per IP (MaxClients is set to 60 in httpd.conf):WARNING! Please note that large proxy servers may legitimately create a large number of connections to your server. You can skip those ips using !

/sbin/iptables -A INPUT -p tcp --syn --dport 80 -m connlimit --connlimit-above 20 -j REJECT --reject-with tcp-reset
# save the changes see iptables-save man page, the following is redhat and friends specific command
service iptables save

Skip proxy server IP 1.2.3.4 from this kind of limitations:

/sbin/iptables -A INPUT -p tcp --syn --dport 80 -d ! 1.2.3.4 -m connlimit --connlimit-above 20 -j REJECT --reject-with tcp-reset

Example: Class C Limitations

In this example, limit the parallel http requests to 20 per class C sized network (24 bit netmask)

/sbin/iptables  -A INPUT -p tcp --syn --dport 80 -m connlimit --connlimit-above 20 --connlimit-mask 24 -j REJECT --reject-with tcp-reset
# save the changes see iptables-save man page
service iptables save

Example: Limit Connections Per Second

The following example will drop incoming connections if IP make more than 10 connection attempts to port 80 within 100 seconds (add rules to your iptables shell script)

#!/bin/bash
IPT=/sbin/iptables
# Max connection in seconds
SECONDS=100
# Max connections per IP
BLOCKCOUNT=10
# ....
# ..
# default action can be DROP or REJECT
DACTION="DROP"
$IPT -A INPUT -p tcp --dport 80 -i eth0 -m state --state NEW -m recent --set
$IPT -A INPUT -p tcp --dport 80 -i eth0 -m state --state NEW -m recent --update --seconds ${SECONDS} --hitcount ${BLOCKCOUNT} -j ${DACTION}
# ....
# ..

How Do I Test My Firewall Working?

Use the following shell script to connect to your web server hosted at 202.1.2.3:

#!/bin/bash
ip="202.1.2.3"
port="80"
for i in {1..100}
do
  # do nothing just connect and exit
  echo "exit" | nc ${ip} ${port};
done

How to password protect the single user mode in Linux

One of the very compromising situation arising with a Linux box with a slack physical security easy access to anyone to the linux box – is one were a malicious user boots into an un protected single user mode and changes your root password. This can be prevented by making your linux machine to ask for the root password even when the system is made to boot into single user mode. The below given tip lets you achieve this goal.

How to implement this Tip?

1. From your Linux machine access a terminal window and open /etc/inittab file for edit.

2. In this file add the below given line just before the id:X:initdefault: entry 

su:S:wait:/sbin/sulogin

3. Save the /etc/ininttab file.

4. Now from next time onwards you will be prompted to provide the root password before accessing the single user mode.

Snort Install Guide for Red Hat Enterprise Linux 5

Snort Install Guide for Red Hat Enterprise Linux 5 to log to MySQL Database

Written by kammo on August 3rd, 2008 This guide is intended for users who are using Red Hat Enterprise Linux 5, but this should work fine, or be rather easy to follow and manipulate for users using earlier versions of RHEL, or other Red Hat based Distorbutions such as CentOS and Fedora.
Pre-requisites: You need to have a MySQL database setup for Snort to log to. See my guide, Create MySQL Database for Snort, on how to setup the MySQL Database.

First Login to the server and su to root:
sudo su –
Then create a source directory for Snort and switch to it:
mkdir /root/snort
cd /root/snort

Download Snort:
Be sure to check the latest version. As of this writing we will be using snort 2.8.2 which is the current.  You can get the latest version by going to http://www.snort.org/dl/ and checking there.

wget http://www.snort.org/dl/old/snort-2.8.2.tar.gz
Uncompress the file:
tar –zxvf snort-2.8.2.tar.gz
Install Dependencies:
yum install libpcap-devel libtool pcre-devel mysql mysql-devel gcc
Install snort:
cd /root/snort/snort-2.8.2
./configure --with-mysql --prefix=/usr
If you get any errors, you probably need to install other dependencies. Google them and try again.
After the ./configure completes successfully, do:
make all
make install
Create Snort user and group:
groupadd snort
useradd –g snort snort

Create Snort Directories:
mkdir –p /etc/snort/rules
mkdir /var/log/snort
Change ownership of log directory:
chown snort.snort /var/log/snort
Copy your rules to /etc/snort/rules. These rules can be downloaded from http://www.snort.org.
Copy the snort.conf file from here and paste it to /etc/snort/snort.conf
Configure MySql information in snort.conf:
vi /etc/snort/snort.conf

Search for log, mysql by typing this exactly:
?alert, mysql
Then press Enter.
This will take you to the line that you will configure MySql logging on.
Set the variables it asks for on that line.  If you don’t know what they are, you probably shouldn’t be doing this install to begin with…
At this point you should go in and setup your rules that you have at the bottom of the file. Just follow the format from the already configured rules.
Add script to /etc/init.d/ to start snort service:
vi /etc/int.d/snortd
press i to enable inserting text.
Copy the following text in gray:
#!/bin/sh
# Description: start up script for snort
# chkconfig: 2345 40 60
#
# Source function library.
. /etc/rc.d/init.d/functions
#
case "$1" in
#
'start')
echo "Starting up Snort..."
/usr/bin/snort -c /etc/snort/snort.conf -D -g snort -u snort -i eth0 -l /var/log/snort
echo "Done."
;;
#
'stop')
echo "Stopping Snort..."
killproc snort
echo "Done."
;;
#
'restart')
$0 stop
$0 start
;;
#
status)
status snort
;;
#
*)
echo "Usage: $0 {start|stop}"
exit 1
#
esac
exit 0
Go back to the ssh client and hold the shift key and press the Insert key (This will paste the script into the file. )
Press the Esc Key to leave insert mode.
Hold the Shift key and press z twice to save and exit the file.
Make the service script executable:
chmod +x /etc/rc.d/init.d/snortd
Start Snort Service at boot:
chkconfig snortd on
Start Snort:
service snortd start
Check that it’s runnig:
ps –ef | grep snort
or
service snortd status
If the only thing you see contains grep then snort is not running.
If this is the case, look at the messages log to see what held it up. Generally it’s a bad rule, which it will tell you what is bad about it.
tail –n100 /var/log/messages

Few Securing a LInux server tips

#Reference:http://www.cisecurity.org/bench_linux.html

#Note:This tutorial is based on Fedora Core 4.Should be valid for a newer version of Fedora too.The reader is advised to read the CIS Benchmark pdf after completing all activities mentioned in this document.

# Setup an informative command prompt
export PS1="-\$?-(\u@\h) \w > "


# Hostname Setup
Reference:http://www.cpqlinux.com/hostname.html

# Please ensure that the correct hostname is setup in the following files.The hostname should ideally match the PTR record of the system IP
/etc/hosts
/etc/sysconfig/network
# Use echo to set the hostname in the file below eg.
echo yourhostname > /proc/sys/kernel/hostname
/proc/sys/kernel/hostname
# Virtual IP Setup
cd /etc/sysconfig/network-scripts

#Check for existing network adapters with the command:

ls ifcfg-*

#In most instances, you will see the files ifcfg-eth0 and ifcfg-lo. If you see other files with any other names and are unfamiliar with configuring TCP/IP, you may want to consult with your system administrator before proceeding.

cp -a ifcfg-eth0 ifcfg-eth0:0
cp -a ifcfg-eth0 ifcfg-eth0:1
# Ensure the following lines are configured as

vi icfg-eth0:0
DEVICE=eth0:0
IPADDR=
VLAN=yes

vi icfg-eth0:1
DEVICE=eth0:1
IPADDR=
VLAN=yes

#Disable IPV6

cp -a /etc/modprobe.conf /etc/modprobe_backup.conf
echo "alias net-pf-10 off" >> /etc/modprobe.conf
echo "alias ipv6 off" >> /etc/modprobe.conf

/etc/init.d/ip6tables stop
/sbin/chkconfig --level 35 ip6tables off

# Restart the network to effect changes

/sbin/service network restart

# Edit /etc/hosts and add a line for your new addresses and name such as:
127.0.0.1 localhost.localdomain localhost
x.x.x.x newhost1.yourdomain.com
x.x.x.x newhost2.yourdomain.com


# Disabling selinux

vi /etc/sysconfig/selinux
#check for the line SELINUX
SELINUX=disabled

# Date and Time Configuration

Ref:http://www.linuxsa.org.au/tips/time.html

ln -sf /usr/share/zoneinfo/Asia/Calcutta /etc/localtime

date monthdayhourminyear

yum install ntp

#Configure a cron job to update time every night at 12 AM
00 00 * * * /usr/sbin/ntpdate 0.pool.ntp.org 1.pool.ntp.org

# Configure Automatic Updates using yum.Fedora Core 6 or above will have yum-updatesd instead of yum

/sbin/chkconfig yum on
/sbin/service yum start

# If you wish to disable autoupdation of some package, eg.firefox and cacti ,do the following
cp -a /etc/yum.conf /etc/yum.conf.orig
vi /etc/yum.conf
# Add the following line
exclude=firefox cacti

# For Fedora Core 6 or above do this
# Reference: http://www.die.net/doc/linux/man/man5/yum-updatesd.conf.5.html
cp -a /etc/updatedb.conf /etc/updatedb.conf.orig
vi /etc/yum/yum-updatesd.conf

#########
# Configure the entries as shown below
# automatically install updates
do_update = yes
# automatically download updates
do_download = yes
# automatically download deps of updates
do_download_deps = yes
#########

/sbin/chkconfig yum-updatesd on
/sbin/service yum-updatesd start

crontab -e

00 0 * * * yum -y update

# Configuring updatedb
cp -a /etc/updatedb.conf /etc/updatedb.conf.orig

vi /etc/updatedb.conf
#Configure the following values to yes
#DAILY_UPDATE=no
DAILY_UPDATE=yes

# Configuring Log Compression
cp -a /etc/logrotate.conf /etc/logrotate.conf.orig
vi /etc/logrotate.conf

# uncomment this if you want your log files compressed
compress

# Unalias cp and mv

unalias mv cp

# Firewall ,Reactive IDS and SSH bruteforce prevention setup

Please install and configure shorewall ,psad and fail2ban by referring their separate howtos

# Apache Installation

# Check if Apache is already installed

rpm -qa httpd
service httpd status

# If httpd is not installed proceed with the apache installation as follows

yum install httpd
yum install httpd-devel


# Apache Hardening

Edit httpd.conf file as follows.

cd /etc/httpd/conf/

cp -a httpd.conf httpd.conf.orig

vi /etc/httpd/conf/httpd.conf

# Edit the following entry as follows

#ServerTokens OS
ServerTokens Prod

#ServerSignature On
ServerSignature Off


#Ref:http://www.slac.stanford.edu/comp/unix/apache-security.html
#http://publib.boulder.ibm.com/httpserv/ihsdiag/http_trace.html

# Disabling Indexing
# Ref: http://www.ducea.com/2006/06/26/apache-tips-tricks-disable-directory-indexes/
# In Main Server Configurations

Options -Indexes

# To disable Trace and Track Methods:

For apache version 1.3.34 (or later 1.3.x versions), or apache 2.0.55 (or later), in section 1, add the line
TraceEnable off

For older versions of apache, see below.

#Add Before Secton 3 and in each virtual host configuration section/file
# Block access: SLAC addition
RewriteEngine On
RewriteCond %{REQUEST_METHOD} ^(TRACE|TRACK)
RewriteRule .* - [F]
# End block access rule

# Disabling welcome page
cp -a /etc/httpd/conf.d/welcome.conf /etc/httpd/conf.d/welcome.conf.orig
vi /etc/httpd/conf.d/welcome.conf
# Comment all the lines in the file

# Disabling configuration by .htaccess

AllowOverride None

# Restart Apache
/etc/rc.d/init.d/httpd start

# MySQL Installation
# Check if MySQL is already installed

rpm -qa mysql
service mysqld status

# If Mysqld Daemon is not installed proceed with the MySQL installation as follows

yum install mysql-server
yum install mysql
yum install mysql-devel

#Start MySQL for the first time

mysql_install_db
/etc/rc.d/init.d/mysqld start
#Note:In case you have issues starting Mysql server for the first time and you see error messggaes saying that tmp files could not be created,please run bastille configuration again and answer N to "Q: Would you like to install TMPDIR/TMP scripts?" question reboot the system.Post reboot you can start Mysqld

/sbin/chkconfig mysqld on

#Mysql Hardening:

mysql
# Removing anonymous login:

DELETE FROM mysql.user WHERE User = '';
FLUSH PRIVILEGES;
quit
#Setting Mysql Root password:

/usr/bin/mysqladmin -u root password 'yourpassword'
/usr/bin/mysqladmin -u root -h password 'yourpassword'

# Delete test database

mysql
drop database test;

# Configure Mysql to not listen for external connections

cp -a /etc/my.cnf /etc/my.cnf.orig

vi /etc/my.cnf

[mysqld]
skip-networking

#Perl Installation

#check if perl is installed or not

rpm -qa perl

# If Perl is not installed proceed with the Perl installation as follows

yum install perl

# Cpan configuration

# Before running cpan ensure that gcc is installed else some modules will throw errors during compilation

rpm -qa gcc

# Install gcc if not found

yum install gcc

# Run and configure cpan

cpan

# A first time set of configuration questions will be asked

# Update cpan by running

cpan
install Bundle::CPAN
reload cpan

# Bastille Hardening


#Bastille Installation

cd /tmp

wget http://nchc.dl.sourceforge.net/sourceforge/bastille-linux/Bastille-3.2.1-0.1.noarch.rpm


# Ref: http://www.bastille-linux.org/running_bastille_on.htm#top

rpm -ivh Bastille-3.2.1-0.1.noarch.rpm

# Install Curses from cpan
# Please check wheather ncurses-devel is installed

rpm -qa ncurses-devel

# If ncurses is not installed install it as follows

yum install ncurses-devel

# Install Curses module as follows

cpan

install Curses

# Run bastille text mode hardening as follows

/usr/sbin/bastille -c

# Respond to all questions

# Check your score

/usr/sbin/bastille --report


# ICMP Hardening


# Check and Download sysctl RPM
yum install sysctl

# Enter the following in /etc/sysctl.conf file
net.ipv4.icmp_echo_ignore_all = 1

net.ipv4.icmp_echo_ignore_broadcasts = 1

net.ipv4.icmp_ignore_bogus_error_responses = 1

net.ipv4.conf.all.accept_source_route = 0

net.ipv4.conf.all.accept_redirects = 0

net.ipv4.tcp_max_syn_backlog = 4096

net.ipv4.tcp_syncookies=1
net.ipv4.conf.all.rp_filter = 1
net.ipv4.conf.all.secure_redirects = 0
net.ipv4.conf.default.rp_filter = 1
net.ipv4.conf.default.accept_source_route = 0
net.ipv4.conf.default.accept_redirects = 0
net.ipv4.conf.default.secure_redirects = 0
net.ipv4.tcp_max_orphans = 256
net.ipv4.conf.all.log_martians = 1

# Diable Forwarding and Gateway functionality
net.ipv4.ip_forward = 0
net.ipv4.conf.all.send_redirects = 0
net.ipv4.conf.default.send_redirects = 0


#Check for the syntax in the file /etc/sysctl.conf
/sbin/sysctl -p

OR
/sbin/iptables -A INPUT -j REJECT -p icmp --icmp-type 13
/sbin/iptables -A OUTPUT -j REJECT -p icmp --icmp-type 14

# Detailed audit trail setup

Ref: http://www.cyberciti.biz/tips/howto-log-user-activity-using-process-accounting.html

yum install psacct
chkconfig psacct on
/etc/init.d/psacct start

# Rootkit Hunter

Reference:http://www.rootkit.nl/

Installation:

# Download rkhunter from http://www.rootkit.nl/projects/rootkit_hunter.html
cd /tmp
wget http://nchc.dl.sourceforge.net/sourceforge/rkhunter/rkhunter-1.3.2.tar.gz
tar zxvf rkhunter-1.3.2.tar.gz
cd rkhunter-1.3.2
sh installer.sh --layout default --install

# Running Rkhunter
/usr/local/bin/rkhunter --update
/usr/local/bin/rkhunter -c --createlogfile --quiet
The report will be generated at /var/log/rkhunter.log

#Configure rkhunter for automatic update
crontab -e
00 0 * * * /usr/local/bin/rkhunter --update -q

# SSHD Hardening
cp -a /etc/ssh/sshd_config /etc/ssh/sshd_config.orig

vi /etc/ssh/sshd_config

#change port no from 22 to 222
Port 222

PermitRootLogin no

Banner /etc/issue

#This banner is generated when you ran Bastille previously.

#Prevent X11 forwarding
X11Forwarding no

#Don't read the user's ~/.rhosts and ~/.shosts files uncomment IgnoreRhosts yes
IgnoreRhosts yes

# The following switch is not found in Fedora 4.Please check the switch to ensure that it exists #before making this entry

RhostsAuthentication no

RhostsRSAAuthentication no

HostbasedAuthentication no

PermitEmptyPasswords no

#Note:Before restarting ssh please create a non-root account.

Restart sshd
/etc/rc.d/init.d/sshd restart
# Nessus Setup

# Read the Nessus How to file for installing and running Nessus

# CIS benchmark security exercise

# Download the CIS benchmark locally from http://www.cisecurity.org/bench_linux.html and copy the do-backup.sh file in /root and run the same to backup all important directories and files

cd /root
chmod 755 do-backup.sh
./do-backup.sh

# Uninstalling xinetd
rpm -qa xinetd
rpm -e xinetd-versionnumber

# Incase you still want to use some services in xinetd ,please run the following comands to stop these unnnecessary services.

cd /etc/xinetd.d
for FILE in chargen chargen-udp cups-lpd cups daytime \ daytime-udp echo echo-udp eklogin ekrb5-telnet finger \ gssftp imap imaps ipop2 ipop3 krb5-telnet klogin kshell \ ktalk ntalk pop3s rexec rlogin rsh rsync servers services \ sgi_fam talk telnet tftp time time-udp vsftpd wu-ftpd do

chkconfig ${FILE} off done

# Disable GUI
sed -e 's/id:5:initdefault:/id:3:initdefault:/' \
< /etc/inittab-preCIS > /etc/inittab
chown root:root /etc/inittab
chmod 0600 /etc/inittab
diff /etc/inittab-preCIS /etc/inittab

# Disable Unneccessary services
# Please review all services listed in the following script before running.

vi disable_unwanted_services

########
for FILE in apmd avahi-daemon canna cups-config-daemon FreeWnn gpm hidd hpoj hplip innd irda isdn kdcrotate lvs mars-nwe messagebus oki4daemon privoxy rstatd rusersd rwalld rwhod wine; do
/sbin/service $FILE stop
/sbin/chkconfig $FILE off
done

for FILE in nfs nfslock autofs ypbind ypserv yppasswdd portmap smb netfs lpd tux snmpd named postgresql webmin kudzu squid cups ip6tables pcmcia bluetooth mDNSResponder; do
/sbin/service $FILE stop
/sbin/chkconfig $FILE off
done
########

chmod 755 disable_unwanted_services
./disable_unwanted_services

# Assign Proper permissions to log files

chmod o-rwx boot.log* cron* dmesg ksyms* httpd/* maillog* messages* news/* pgsql rpmpkgs* samba/* sa/* scrollkeeper.log secure* spooler* squid/* vbox/* wtmp

chmod o-rx boot.log* cron* maillog* messages* pgsql secure* spooler* squid/* sa/*

chmod g-w boot.log* cron* dmesg httpd/* ksyms* maillog* messages* pgsql rpmpkgs* samba/* sa/* scrollkeeper.log secure* spooler*

chmod g-rx boot.log* cron* maillog* messages* pgsql secure* spooler*

chmod o-w gdm/ httpd/ news/ samba/ squid/ sa/ vbox/

chmod o-rx httpd/ samba/ squid/ sa/

chmod g-w gdm/ httpd/ news/ samba/ squid/ sa/ vbox/

chmod g-rx httpd/ samba/ sa/

chmod u-x kernel syslog loginlog

# Verify passwd, shadow, and group File Permissions

cd /etc
chown root:root passwd shadow group
chmod 644 passwd group
chmod 400 shadow

# Allowing only root access to Cron and At

cd /etc/
rm -f cron.deny at.deny
echo root > cron.allow
echo root > at.allow
chown root:root cron.allow at.allow
chmod 400 cron.allow at.allow

# Restrict Permissions On crontab Files

chown root:root /etc/crontab
chmod 400 /etc/crontab
chown -R root:root /var/spool/cron
chmod -R go-rwx /var/spool/cron
cd /etc
ls | grep cron | grep -v preCIS | xargs chown -R root:root
ls | grep cron | grep -v preCIS | xargs chmod -R go-rwx

# Block all system accounts from loging on to the server

cd /root
vi lock_system_accounts

####
cd /etc
for NAME in `cut -d: -f1 /etc/passwd`; do
MyUID=`id -u $NAME`
if [ $MyUID -lt 500 -a $NAME != 'root' ]; then
/usr/sbin/usermod -L -s /dev/null $NAME
fi
done
###

chmod 755 lock_system_accounts

./lock_system_accounts

rm -rf lock_system_accounts

# Check for empty password accounts
awk -F: '($2 == "") { print $1 }' /etc/shadow

# Set Account Expiration Parameters On Active Accounts

cd /etc
awk '($1 ~ /^PASS_MAX_DAYS/) { $2="90" }
($1 ~ /^PASS_MIN_DAYS/) { $2="7" }
($1 ~ /^PASS_WARN_AGE/) { $2="28" }
($1 ~ /^PASS_MIN_LEN/) { $2="6" }
{ print } ' login.defs-preCIS > login.defs
diff login.defs-preCIS login.defs
chown root:root login.defs
chmod 640 login.defs
diff login.defs-preCIS login.defs

useradd -D -f 7
diff /etc/default/useradd-preCIS /etc/default/useradd
for NAME in `cut -d: -f1 /etc/passwd`; do
uid=`id -u $NAME`
if [ $uid -ge 500 -a $uid != 65534 ]; then
chage -m 7 -M 90 -W 28 -I 7 $NAME
fi
done
diff shadow-preCIS shadow

# Verify No Legacy '+' Entries Exist In passwd, shadow, And group Files

grep ^+: /etc/passwd /etc/shadow /etc/group

# No '.' or Group/World-Writable Directory In Root's $PATH

#To find ‘.’ in $PATH:
echo $PATH | egrep '(^|:)(\.|:|$)'
#To find group- or world-writable directories in $PATH:
find `echo $PATH | tr ':' ' '` -type d \( -perm -002 -o -perm -020 \) -ls

#These commands should produce no output.

#User Home Directories Should Be Mode 750 or More Restrictive

vi user_directories_permission

###############
for DIR in `awk -F: '($3 >= 500) { print $6 }' /etc/passwd`; do
chmod g-w $DIR
chmod o-rwx $DIR
done
##############

chmod 755 user_directories_permission
./user_directories_permission

#No User Dot-Files Should Be World-Writable

vi user_dot_files_non_worldwritable

#############

for DIR in `awk -F: '($3 >= 500) { print $6 }' /etc/passwd`; do
for FILE in $DIR/.[A-Za-z0-9]*; do
if [ ! -h "$FILE" -a -f "$FILE" ]; then
chmod go-w "$FILE"
fi
done
done
#########

chmod 755 user_dot_files_non_worldwritable
./user_dot_files_non_worlwritable

#Remove User .netrc Files

find / -name .netrc

# If any .netrc file is found then run the following script to remove

vi remove_netrc

###############
for DIR in `cut -f6 -d: /etc/passwd`; do
if [ -e $DIR/.netrc ]; then
echo "Removing $DIR/.netrc"
rm -f $DIR/.netrc fi
done
###############

chmod 755 remove_netrc
./remove_netrc

#Set Default umask For Users

vi set_default_umask

#########
cd /etc
for FILE in profile csh.login csh.cshrc bashrc; do
if ! egrep -q 'umask.*77' $FILE ; then
echo "umask 077" >> $FILE
fi
chown root:root $FILE
chmod 444 $FILE
diff ${FILE}-preCIS $FILE
done

cd /root
for FILE in .bash_profile .bashrc .cshrc .tcshrc; do
if ! egrep -q 'umask.*77' $FILE ; then
echo "umask 077" >> $FILE # See description
fi
chown root:root $FILE
diff ${FILE}-preCIS $FILE
done
###########

chmod 755 set_default_umask
./set_default_umask


# Disable Core Dumps

cp -a /etc/security/limits.conf /etc/security/limits.conf.orig

vi /etc/security/limits.conf

#Add the following two lines.In future you can enable core dumps for invidual users if required.

* soft core 0
* hard core 0

####

# Limit Access To The Root Account From su
# Warning:Please add your account to the wheel group before proceeding with this activity else you # will not be able to su.
# eg. /usr/sbin/usermod -G wheel

# In case you want to create a new account and add it to the wheel group, then run this command
/usr/sbin/useradd -G wheel

# Limit Access To The Root Account From su

cd /etc/pam.d/
cp -a su su_backup_18_dec_2006

vi su

##Uncommenting this line allows only the users in the wheel group to become root by using the su command and entering the root password.All other users get the message Incorrect Password

auth required /lib/security/$ISA/pam_wheel.so use_uid

# Banners

# Note:/etc/issue banner should have already been created by BastilleIf you havent run Bastille please create an appropriate banner file /etc/issue as follows



***************************************************************************
NOTICE TO USERS


This computer system is the private property of , whether
individual, corporate or government. It is for authorized use only.
Users (authorized or unauthorized) have no explicit or implicit
expectation of privacy.

Any or all uses of this system and all files on this system may be
intercepted, monitored, recorded, copied, audited, inspected, and
disclosed to your employer, to authorized site, government, and law
enforcement personnel, as well as authorized officials of government
agencies, both domestic and foreign.

By using this system, the user consents to such interception, monitoring,
recording, copying, auditing, inspection, and disclosure at the
discretion of such personnel or officials. Unauthorized or improper use
of this system may result in civil and criminal penalties and
administrative or disciplinary action, as appropriate. By continuing to use
this system you indicate your awareness of and consent to these terms
and conditions of use. LOG OFF IMMEDIATELY if you do not agree to the
conditions stated in this warning.

****************************************************************************
cp -a issue.net issue_backup_todays_date.net

cp -a issue issue.net

# Contents of /etc/motd are displayed after a user logins in so its not neccessary to create a #banner in that file

chown root:root /etc/motd /etc/issue /etc/issue.net
chmod 644 /etc/motd /etc/issue /etc/issue.net

# Removing unnecessary applications
# Please refer http://www.mjmwired.net/resources/mjm-services-fc6.html for the list of services and their uses and recommendations on which to disable
cd /etc/init.d
ls

# Verify the softwares that are listed here.Remove all unnecesaasy packages as show below.

# For eg. if you see bluetooth and you want to identify what package it represnts, do the following
rpm -qf bluetooth
bluez-utils-2.15-7
yum remove bluez-utils-2.15-7

# Do this for all other softwares like portmap,apmd,cups,isdn,irda,etc.

# RHEL comes with virtualisation enabled.Due to this you may see an additional network adapter ( virbr0 ) when you run /sbin/ifconfig -a
# This can be removed by following these steps
#Source :http://www.cyberciti.biz/faq/rhel-fedora-centos-linux-remove-network-interface-virbr0/
yum groupremove "Virtualization"

# Type y when it lists the following pakcages to be removed
libvirt
libvirt-python
rhn-virtualization-host

This will also remove the virbr0 network adapter

#Firewall Configuration

/bin/netstat -ltunp

# The above command will show you list of processes running on specific ports.Please ensure that unnecassary services are disabled and uninstalled as shown in the above point.
# Open required ports in iptables using Shorewall (Please refer the separate Howto)
/usr/sbin/lokkit

# Remove All Compilers and Assemblers

#The following command will help you identify the packages installed on your system
rpm -qa | egrep "^gcc|java|bin86|dev86|nasm"

#Identify the package and remove the ones you dont need

#Verify That No Unauthorized UID 0 Accounts Exists

getent passwd | awk -F: '$3 == "0" { print $1 }'

#should return only the word "root", unless additional uid 0 accounts have been specifically authorized. Having #multiple uid 0 accounts are acceptable if the accounts are authorized, but not recommended for

Shorewall setup to ease your Iptables setup

Reference:
http://www.shorewall.net/shorewall_setup_guide.htm


# Backup your existing Iptables configuration so that you can revert back in case something goes wrong

cp -a /etc/sysconfig/iptables /etc/sysconfig/iptables_backup_

# Deploying a safety net to ensure that you dont get locked out
Reference : http://www.iptablesrocks.org/guide/safetynet.php
vi /root/firewall_reset

############
# Iptables firewall reset script
*filter
:INPUT ACCEPT [164:15203]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [147:63028]
COMMIT

*mangle
:PREROUTING ACCEPT [164:15203]
:INPUT ACCEPT [164:15203]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [147:63028]
:POSTROUTING ACCEPT [147:63028]
COMMIT

*nat
:PREROUTING ACCEPT [14:672]
:POSTROUTING ACCEPT [9:684]
:OUTPUT ACCEPT [9:684]
COMMIT

###########

# Test if the above script works and throws no error

/sbin/iptables-restore < /root/firewall_reset

/sbin/iptables -L

# The output should be similar to the following
###
Chain FORWARD (policy ACCEPT)
target prot opt source destination

Chain INPUT (policy ACCEPT)
target prot opt source destination

Chain OUTPUT (policy ACCEPT)
target prot opt source destination
###

# restore your orginal firewall configuration and proceed

/sbin/iptables-restore < /etc/sysconfig/iptables_backup_

# Confirm that your original rules have been restored by running the following command

/sbin/iptables -L

# Create a crontab entry that resets the firewall every 15 minutes

crontab -e

0,15,30,45 * * * * /sbin/iptables-restore < /root/firewall_reset

# Please ensure that you comment out this line after you have succesfully tested you shorewall working.


# Reference:http://www.shorewall.net/shorewall_quickstart_guide.htm

# Before installing ,check if iproute and shorewall already exist

rpm -qa | grep -i "iproute"
rpm -qa | grep -i "shorewall"

# If iproute doesn't exist then proceed as follows

yum install iproute

# Shorewall Installation

# Using Yum
yum install shorewall

# Using RPM
# In most cases shorewall would not exist in yum repositories so proceed as follows for the rpm installation

References :
http://www.shorewall.net/Install.htm
http://www.shorewall.net/download.htm

Download the shorewall and shorewall-perl rpm package

cd /tmp

wget http://www.invoca.ch/pub/packages/shorewall/4.2/shorewall-4.2.5/shorewall-4.2.5-3.noarch.rpm

wget http://www.invoca.ch/pub/packages/shorewall/4.2/shorewall-4.2.5/shorewall-perl-4.2.5-3.noarch.rpm

rpm -ivh shorewall-perl-4.2.5-3.noarch.rpm shorewall-4.2.5-3.noarch.rpm

#Setting up Shorewall on a standalone Linux system with a single static IP address
Reference :http://www.shorewall.net/standalone.htm

# Add your IP address (IP address of the system/gateway you are connecting from and not the server IP address where you are installing shorewall) to the /etc/shorewall/routestopped file to ensure that you stay connected when the firewall restarts.You can find your IP address by visiting http://whatismyip.com
cp -a /etc/shorewall/routestopped /etc/shorewall/routestopped.orig

vi /etc/shorewall/routestopped
# eg. if your IP address ( the system/gateway you are connecting from) is 59.144.118.69
#INTERFACE HOST(S)
eth0 59.144.0.0/24

# You can also add a CIDR number to indicate a range of IPs from which connection will not break
# For eg. if you want to keep alive connections from 192.168.0.1 to 192.168.0.254 during the firewall restart add the following line

#INTERFACE HOST(S)
eth0 192.168.0.0/24

# Find the sample configuration files by running

rpm -ql shorewall | fgrep one-interface

cp -a /usr/share/doc/shorewall-4.2.5/Samples/one-interface /tmp/


cd /tmp/one-interface
# Confirm your ethernet interface ( to check if you have a single lan card)

/sbin/ifconfig -a

vi interfaces

########
#ZONE INTERFACE BROADCAST OPTIONS
net eth0 210.210.18.90 norfc1918,routefilter,tcpflags,logmartians,nosmurfs
########

# The BROADCAST address can be ignored above and instead you can put a -

#RFC-1918 reserves several Private IP address ranges for use in private networks:

10.0.0.0 - 10.255.255.255
172.16.0.0 - 172.31.255.255
192.168.0.0 - 192.168.255.255

#If your IP address falls in any of the above range, then please remove "norfc1918" in the options section of the interfaces file
# If you have a non-static DHCP IP address,add "detect" in the "broadcast" section and add “dhcp” to the option list.

# Configuration of rules

# You can find custom rules files by running

ls /usr/share/shorewall/macro.*

# You can then use these macros in your shorewall rules file

# For eg. if you want to allow access to your web server running TCP Port 80 and SSHD running on TCP port 22 do the following

# Tip: You can identify the network services running on your server bu issuing the following command.

/bin/netstat -luntp

# Based on the output you get , you can decide which services to allow remote access or not

cd /tmp/one-interface

vi rules

#######
#ACTION SOURCE DESTINATION PROTO DEST PORT(S)
Web/ACCEPT net $FW
SSH/ACCEPT net $FW
######


# You can also add the above rules in this way.

vi rules

#########
#ACTION SOURCE DESTINATION PROTO DEST PORT(S)
ACCEPT net $FW tcp 80
ACCEPT net $FW tcp 22
#########
# You can also add the following rule if you see port TCP 113 as closed in your nmap scan.
DROP net $FW tcp 113

If you want to allow conections to let's say the ssh port only from specific IP Addresses on the internet add the following

ACCEPT net:192.0.2.16/28,192.0.2.44 fw tcp 22

# Please ensure that you check the individual macros you applies from /usr/share/shorewall/macro.* to ensure that they work as desired


# You must enable startup by editing /etc/shorewall/shorewall.conf and setting STARTUP_ENABLED=Yes

cp -a /tmp/one-interface/shorewall.conf /tmp/one-interface/shorewall.conf.orig
vi /tmp/one-interface/shorewall.conf
# Modify the lines as shown

#STARTUP_ENABLED=No
STARTUP_ENABLED=Yes
#IPTABLES=
IPTABLES=/sbin/iptables
#IP_FORWARDING=On
IP_FORWARDING=Off
#DISABLE_IPV6=Yes

# Copy your configuration files to appropriate locations

cd /etc/shorewall/
cp -a policy policy.orig
cp -a rules rules.orig
cp -a interfaces interfaces.orig
cp -a zones zones.orig

cp -a /tmp/one-interface/* /etc/shorewall/

rm -rf /tmp/one-interface/

/etc/rc.d/init.d/shorewall restart

# You can use the following command to clear all shorewall rules
/sbin/shorewall clear

# Configure shorewall to auto start at boot time

/sbin/chkconfig shorewall on

# Use nmap from a different system to ensure that your firewall rules are in place

# Multiple IP address to single interface

# Reference:http://www.shorewall.net/Shorewall_and_Aliased_Interfaces.html#id2491727

# Ensure that all IP addresses ( non virtual ie. additional IP addresses on separate lan cards ) are configured in the /etc/shorewall/interfaces
# eg.

vi /etc/shorewall/interfaces

#ZONE INTERFACE BROADCAST OPTIONS
net eth1 210.210.23.26 norfc1918,routefilter,tcpflags,logmartians,nosmurfs

# The BROADCAST address can be ignored above and instead you can put a -

#RFC-1918 reserves several Private IP address ranges for use in private networks:

10.0.0.0 - 10.255.255.255
172.16.0.0 - 172.31.255.255
192.168.0.0 - 192.168.255.255

#If your IP address falls in any of the above range, then please remove "norfc1918" in the options section of the interfaces file
# If you have a non-static DHCP IP address,add "detect" in the "broadcast" section and add “dhcp” to the option list.

# If you are using virtual IP addresses (eg. eth0:0,eth0:1 etc,) configured for a single ethernet card, then you can ignore the above setting in /etc/shorewall/interfaces

# If you have muliple IP addresses and want a sshd to be available on a single IP address (eg. 210.210.23.26 )instead of all IP adresses on the server ,then do this

vi /etc/shorewall/rules

#ACCEPT net $FW tcp 22
ACCEPT net $FW:210.210.23.26 tcp 22

/sbin/shorewall clear
/etc/rc.d/init.d/shorewall restart

# Remove the firewall_reset cron job and the entries in /etc/shorewall/routestopped after shorewall is run and firewall behaves as expected.

Fail2ban Installation guide :Prevent automated SSH attacks

##Manual Installation

# Download Fail2ban from http://www.fail2ban.org/wiki/index.php/Downloads

cd /tmp
wget http://nchc.dl.sourceforge.net/sourceforge/fail2ban/fail2ban-0.8.3.tar.bz2

tar jxvf fail2ban-0.8.3.tar.bz2
rm -rf /tmp/fail2ban-0.8.3.tar.bz2
cd fail2ban-0.8.3

./setup.py install

cd /tmp/fail2ban-0.8.3/files

cp -a redhat-initd /etc/init.d/fail2ban

cd /etc/init.d/

chown root.root fail2ban

chmod 755 fail2ban

/sbin/chkconfig --add fail2ban

/sbin/chkconfig fail2ban on

cd /etc/fail2ban

cp -a jail.conf jail.conf.orig

vi /etc/fail2ban/jail.conf

Edit values as follows
##########
# Put space separated list of IPs you want to ignore
ignoreip = x.x.x.x



[[ssh-iptables]

#enabled = false
enabled = true
filter = sshd
#action = iptables[name=SSH, port=ssh, protocol=tcp]
# sendmail-whois[name=SSH, dest=you@mail.com, sender=fail2ban@mail.com]
action = iptables[name=SSH, port=ssh, protocol=tcp]
sendmail-whois[name=SSH, dest=admin@yourdomain.com, sender=fail2ban@mail.com]
#logpath = /var/log/sshd.log
logpath = /var/log/secure
#maxretry = 5
maxretry = 3

############

Edit Shorewall configuration (if you are using one as follow)

vi /etc/shorewall/shorewall.conf
#########
#BLACKLISTNEWONLY=Yes
BLACKLISTNEWONLY=No
##########

cd /etc/fail2ban

chown root.root fail2ban.conf
chmod 644 fail2ban.conf

# Log rotation of Fail2ban Logs

cd /etc/logrotate.d

vi fail2ban

###
/var/log/fail2ban.log {
missingok
notifempty
copytruncate
}
###

chown root.root fail2ban
chmod 644 fail2ban

/etc/rc.d/init.d/fail2ban start

# Check fail2ban.log for any errors

tail -f /var/log/fail2ban.log

rm -rf /tmp/fail2ban-0.8.3

 Reference: http://www.fail2ban.org/wiki/index.php/MANUAL_0_8

psad: Linux Detect And Block Port Scan Attacks In Real Time

detect port scan attacks by analyzing Debian Linux firewall log files and block port scans in real time? How do I detect suspicious network traffic under Linux?

  A port scanner (such as nmap) is a piece of software designed to search a network host for open ports. Cracker can use nmap to scan your network before starting attack. You can always see scan patterns by visiting /var/log/messages. But, I recommend the automated tool called psad - the port scan attack detector under Linux which is a collection of lightweight system daemons that run on Linux machines and analyze iptables log messages to detect port scans and other suspicious traffic.
psad makes use of Netfilter log messages to detect, alert, and (optionally) block port scans and other suspect traffic. For tcp scans psad analyzes tcp flags to determine the scan type (syn, fin, xmas, etc.) and corresponding command line options that could be supplied to nmap to generate such a scan. In addition, psad makes use of many tcp, udp, and icmp signatures contained within the Snort intrusion detection system.

Install psad under Debian / Ubuntu Linux

Type the following command to install psad, enter:
$ sudo apt-get update
$ sudo apt-get install psad

Or You can Download it from :- http://www.cipherdyne.org/psad/download/


Configure psad

Open /etc/syslog.conf file, enter:
# vi /etc/syslog.conf
Append following code

kern.info       |/var/lib/psad/psadfifo

Alternatively, you can type the following command to update syslog.conf:
echo -e ’kern.info\t|/var/lib/psad/psadfifo’ >> /etc/syslog.conf
psad Syslog needs to be configured to write all kern.info messages to a named pipe /var/lib/psad/psadfifo. Close and save the file. Restart syslog:
# /etc/init.d/sysklogd restart
# /etc/init.d/klogd
The default psad file is located at /etc/psad/psad.conf:
# vi /etc/psad/psad.conf
You need to setup correct email ID to get port scan detections messages and other settings as follows:

EMAIL_ADDRESSES             vivek@nixcraft.in;

Set machine hostname (FQDN):

HOSTNAME                    server.nixcraft.in;

If you have only one interface on box (such as colo web server or mail server), sent HOME_NET to none:

HOME_NET                NOT_USED;  ### only one interface on box

You may also need to adjust danger levels as per your setup. You can also define a set of ports to ignore, for example to have psad ignore udp ports 53 and 5000, use:

IGNORE_PORTS                udp/53, udp/5000;

You can also enable real time iptables blocking, by setting following two variables:

ENABLE_AUTO_IDS             Y;
IPTABLES_BLOCK_METHOD       Y;

psad has many more options, please read man pages for further information. Save and close the file. Restart psad:
# /etc/init.d/psad restart

Update iptables rules

psad need following two rules with logging enabled:

iptables -A INPUT -j LOG
iptables -A FORWARD -j LOG 

Here is my sample Debian Linux desktop firewall script with logging enabled at the end:

#!/bin/bash
IPT="/sbin/iptables"
 
echo "Starting IPv4 Wall..."
$IPT -F
$IPT -X
$IPT -t nat -F
$IPT -t nat -X
$IPT -t mangle -F
$IPT -t mangle -X
modprobe ip_conntrack
 
BADIPS=$(egrep -v -E "^#|^$" /root/scripts/blocked.fw)
PUB_IF="eth0"
 
#unlimited
$IPT -A INPUT -i lo -j ACCEPT
$IPT -A OUTPUT -o lo -j ACCEPT
 
# DROP all incomming traffic
$IPT -P INPUT DROP
$IPT -P OUTPUT DROP
$IPT -P FORWARD DROP
 
# block all bad ips
for ip in $BADIPS
do
    $IPT -A INPUT -s $ip -j DROP
    $IPT -A OUTPUT -d $ip -j DROP
done
 
# sync
$IPT -A INPUT -i ${PUB_IF} -p tcp ! --syn -m state --state NEW  -m limit --limit 5/m --limit-burst 7 -j LOG --log-level 4 --log-prefix "Drop Syn"
 
$IPT -A INPUT -i ${PUB_IF} -p tcp ! --syn -m state --state NEW -j DROP
 
# Fragments
$IPT -A INPUT -i ${PUB_IF} -f  -m limit --limit 5/m --limit-burst 7 -j LOG --log-level 4 --log-prefix "Fragments Packets"
$IPT -A INPUT -i ${PUB_IF} -f -j DROP
 
# block bad stuff
$IPT  -A INPUT -i ${PUB_IF} -p tcp --tcp-flags ALL FIN,URG,PSH -j DROP
$IPT  -A INPUT -i ${PUB_IF} -p tcp --tcp-flags ALL ALL -j DROP
 
$IPT  -A INPUT -i ${PUB_IF} -p tcp --tcp-flags ALL NONE -m limit --limit 5/m --limit-burst 7 -j LOG --log-level 4 --log-prefix "NULL Packets"
$IPT  -A INPUT -i ${PUB_IF} -p tcp --tcp-flags ALL NONE -j DROP # NULL packets
 
$IPT  -A INPUT -i ${PUB_IF} -p tcp --tcp-flags SYN,RST SYN,RST -j DROP
 
$IPT  -A INPUT -i ${PUB_IF} -p tcp --tcp-flags SYN,FIN SYN,FIN -m limit --limit 5/m --limit-burst 7 -j LOG --log-level 4 --log-prefix "XMAS Packets"
$IPT  -A INPUT -i ${PUB_IF} -p tcp --tcp-flags SYN,FIN SYN,FIN -j DROP #XMAS
 
$IPT  -A INPUT -i ${PUB_IF} -p tcp --tcp-flags FIN,ACK FIN -m limit --limit 5/m --limit-burst 7 -j LOG --log-level 4 --log-prefix "Fin Packets Scan"
$IPT  -A INPUT -i ${PUB_IF} -p tcp --tcp-flags FIN,ACK FIN -j DROP # FIN packet scans
 
$IPT  -A INPUT -i ${PUB_IF} -p tcp --tcp-flags ALL SYN,RST,ACK,FIN,URG -j DROP
 
# Allow full outgoing connection but no incomming stuff
$IPT -A INPUT -i eth0 -m state --state ESTABLISHED,RELATED -j ACCEPT
$IPT -A OUTPUT -o eth0 -m state --state NEW,ESTABLISHED,RELATED -j ACCEPT
 
# allow ssh only
$IPT -A INPUT -p tcp --destination-port 22 -j ACCEPT
$IPT -A OUTPUT -p tcp --sport 22 -j ACCEPT
 
# allow incoming ICMP ping pong stuff
$IPT -A INPUT -p icmp --icmp-type 8 -m state --state NEW,ESTABLISHED,RELATED -j ACCEPT
$IPT -A OUTPUT -p icmp --icmp-type 0 -m state --state ESTABLISHED,RELATED -j ACCEPT
 
# No smb/windows sharing packets - too much logging
$IPT -A INPUT -p tcp -i eth0 --dport 137:139 -j REJECT
$IPT -A INPUT -p udp -i eth0 --dport 137:139 -j REJECT
 
# Log everything else
# *** Required for psad ****
$IPT -A INPUT -j LOG
$IPT -A FORWARD -j LOG
$IPT -A INPUT -j DROP
 
# Start ipv6 firewall
# echo "Starting IPv6 Wall..."
/root/scripts/start6.fw
 
exit 0

How do I view port scan report?

Simply type the following command:
# psad -S
Sample output (some of the sensitive / personally identified parts have been removed):

[+] psadwatchd (pid: 2540)  %CPU: 0.0  %MEM: 0.0
    Running since: Sun Jul 27 07:14:56 2008

[+] kmsgsd (pid: 2528)  %CPU: 0.0  %MEM: 0.0
    Running since: Sun Jul 27 07:14:55 2008

[+] psad (pid: 2524)  %CPU: 0.0  %MEM: 0.8
    Running since: Sun Jul 27 07:14:55 2008
    Command line arguments: -c /etc/psad/psad.conf
    Alert email address(es): radhika.xyz@xxxxxxxx.co.in

    src:            dst:            chain:  intf:  tcp:  udp:  icmp:  dl:  alerts:  os_guess:
    117.32.xxx.149  xx.22.zz.121    INPUT   eth0   1     0     0      2    2        -
    118.167.xxx.219 xx.22.zz.121    INPUT   eth0   1     0     0      2    2        -
    118.167.xxx.250 xx.22.zz.121    INPUT   eth0   1     0     0      2    2        -
    118.167.xxx.5   xx.22.zz.121    INPUT   eth0   1     0     0      2    2        -
    122.167.xx.11   xx.22.zz.121    INPUT   eth0   4642  0     0      4    50       -
    122.167.xx.80   xx.22.zz.121    INPUT   eth0   0     11    0      1    2        -
    123.134.xx.34   xx.22.zz.121    INPUT   eth0   20    0     0      2    9        -
    125.161.xx.3    xx.22.zz.121    INPUT   eth0   0     9     0      1    4        -
    125.67.xx.7     xx.22.zz.121    INPUT   eth0   1     0     0      2    2        -
    190.159.xxx.220 xx.22.zz.121    INPUT   eth0   0     9     0      1    3        -
    193.140.xxx.210 xx.22.zz.121    INPUT   eth0   0     10    0      1    2        -
    202.xx.23x.196  xx.22.zz.121    INPUT   eth0   0     13    0      1    10       -
    202.xx.2x8.197  xx.22.zz.121    INPUT   eth0   0     20    0      2    17       -
    202.97.xxx.198  xx.22.zz.121    INPUT   eth0   0     17    0      2    12       -
    202.97.xxx.199  xx.22.zz.121    INPUT   eth0   0     18    0      2    15       -
    202.97.xxx.200  xx.22.zz.121    INPUT   eth0   0     17    0      2    14       -
    202.97.xxx.201  xx.22.zz.121    INPUT   eth0   0     15    0      2    12       -
    202.97.xxx.202  xx.22.zz.121    INPUT   eth0   0     21    0      2    16       -
    203.xxx.128.65  xx.22.zz.121    INPUT   eth0   12    0     0      2    6        Windows XP/2000
    211.90.xx.14    xx.22.zz.121    INPUT   eth0   1     0     0      2    2        -
    213.163.xxx.9   xx.22.zz.121    INPUT   eth0   0     0     1      2    2        -
    221.130.xxx.124 xx.22.zz.121    INPUT   eth0   0     35    0      2    31       -
    221.206.xxx.10  xx.22.zz.121    INPUT   eth0   0     33    0      2    21       -
    221.206.xxx.53  xx.22.zz.121    INPUT   eth0   0     33    0      2    27       -
    221.206.xxx.54  xx.22.zz.121    INPUT   eth0   0     39    0      2    26       -
    221.206.xxx.57  xx.22.zz.121    INPUT   eth0   0     33    0      2    19       -
    60.222.xxx.146  xx.22.zz.121    INPUT   eth0   0     40    0      2    33       -
    60.222.xxx.153  xx.22.zz.121    INPUT   eth0   0     14    0      1    11       -
    60.222.xxx.154  xx.22.zz.121    INPUT   eth0   0     18    0      2    15       -

    Netfilter prefix counters:
        "SPAM DROP Block": 161519
        "Drop Syn Attacks": 136

    Total scan sources: 95
    Total scan destinations: 1

    Total packet counters:
        tcp:  5868
        udp:  164012
        icmp: 2

How do I remove automatically blocked ips?

Simply type the following command to remove any auto-generated firewall block
# psad -F

How do I view detailed log for each IP address?

Go to /var/log/psad/ip.address/ directory. For example, view log for IP address 11.22.22.33, enter:
# cd /var/log/psad/11.22.22.33
# ls -l
Sample output:

-rw------- 1 root root 2623 2008-07-30 13:02 xx.22.zz.121_email_alert
-rw------- 1 root root   32 2008-07-30 13:02 xx.22.zz.121_packet_ctr
-rw------- 1 root root    0 2008-07-29 00:27 xx.22.zz.121_signatures
-rw------- 1 root root   11 2008-07-30 13:02 xx.22.zz.121_start_time
-rw------- 1 root root    2 2008-07-30 13:02 danger_level
-rw------- 1 root root    2 2008-07-30 13:02 email_count
-rw------- 1 root root 1798 2008-07-29 00:27 whois

How do I find open ports on Linux server?

There are different commands on both Linux and UNIX server to find out what tcp/udp ports are listening or open on your own server. You can use netstat command, which print network connections, routing tables, interface statistics, masquerade connections, and multicast memberships etc. Another (and suggested) option is to use lsof command, which list open files, and ports on Linux, FreeBSD, Solaris and other Unixish systems.

netstat command to find open ports

# netstat --listenDisplay open ports and established TCP connections:$ netstat -vatnFor UDP port try following command:$ netstat -vaunIf you want to see FQDN, remove -n flag:$ netstat -vat

lsof Command Examples

Display list of open ports
# lsof -iTo display all open files, use:# lsofTo display all open IPv4 network files in use by the process whose PID is 9255, use:
# lsof -i 4 -a -p 9255

Restrict Access To A Given Command

Linux / UNIX: Restrict Access To A Given Command

How do I restrict access to a given command for instance /opt/apps/start, to authorized users only under Linux / UNIX / BSD operating system?

You need to use traditional Unix groups concept to enhance security including restricted access to a given command.

Step # 1: Create and Maintain a Group For All Authorized Users

Create a group named appsonly:
# groupadd appsonly
Add all authorized users to appsonly:
# usermod -aG {groupName} {userName}
# usermod -aG appsonly tom
# usermod -aG appsonly jerry
# id jerry
Where,

1. -a : Add the user to the supplemental group(s) i.e. appends the user to the current supplementary group list.
2. -G : A list of supplementary groups which the user is also a member of.

Step #2: Restrict Access

Now a group of user had been created. Next, use the chgrp command to change the group of /opt/apps/start to appsonly group:
# chgrp {groupName} {/path/to/command}
# chgrp appsonly /opt/apps/start

Disable the file permission for others

Finally, use the chmod command to change file permission as follows:
# chmod 750 /path/to/command
# chmod 750 /opt/apps/start
You can also apply permissions to directory (this will disable ls command access to others) :
# chgrp appsonly /opt/apps
# chmod 0640 /opt/apps

Step # 3: Test It

su to tom, enter:
# su - tom
$ id
$ /opt/apps/start
$ exit
su to vivek (not a member of appsonly group), enter:
# su - vivek
$ id
$ /opt/apps/start
Sample outputs:

bash: /opt/apps/start: Permission denied

A Note About ACL and SELinux

The access control policies which can be enforced by chmod, chgrp, and usermod commands are limited, and configuring SELinux and fille system ACLs (access control list) is a better and recommend option for large deployments.

SSHFS: How do you install sshfs on CentOS/Linux/Redhat

What is sshfs and why would you want it? Well simply put, sshfs allows you to mount another server’s filesystem into a folder on your local system which in the background is doing ssh commands and transfers.
As a mounted folder, you are able to move about and copy files back and forth as everything was on local server. As you can see this makes it very easy for you to work with files on multiple servers.

Note: you only have to do the following installations on the server where you are doing the mounts on.

Let us download and install the filesystem framework which is a requirement for sshfs called fuse.


yum -y install kernel-devel fuse fuse-ntfs-3g dkms dkms-fuse


Once installed, you will have to find out the directory it is installed in


At this point we can try doing the mount again.
cd /mnt
sshfs 10.0.0.2:/ test

If you do not get any errors, do df -h to see the mount:
...
sshfs#10.0.0.2:/ 1000G 0 1000G 0% /mnt/test