Harden and Secure a Linux/cPanel Server

Here I am describing some easier steps to secure a Linux based server. So of the steps are applicable only for cPanel installed servers.

1.)chkrootkit (Check Rootkit) is a common Unix-based program intended to help system administrators check their system for known rootkits

cd /usr/local/src
wget ftp://ftp.pangeia.com.br/pub/seg/pac/chkrootkit.tar.gz
wget ftp://ftp.pangeia.com.br/pub/seg/pac/chkrootkit.tar.gz
tar -xzf chkrootkit.tar.gz
cd chkrootkit-0.50
make sense
cd ..

Adding program to daily cron job
You can add a cron entry for running chkrootkit automatically and send a scan report to your mail address.
Create and add the following entries to “/etc/cron.daily/chkrootkit.sh”

) | /bin/mail -s ‘CHROOTKIT Daily Run (ServerName)’ [email protected]
chmod +x /etc/cron.daily/chkrootkit.sh

2.)RootKit Hunter – A tool which scans for backdoors and malicious softwares present in the server.
cd /usr/local/src
wget http://downloads.sourceforge.net/projec ... 4.2.tar.gz
tar -zxvf rkhunter*
cd rkhunter*
./installer.sh --install
rkhunter --check
log : /var/log/rkhunter.log

To update it
rkhunter --update
rkhunter --propupd

How to setup a daily scan report
pico /etc/cron.daily/rkhunter.sh

set crontab to scan and email the report

/usr/local/bin/rkhunter –versioncheck
/usr/local/bin/rkhunter –update
/usr/local/bin/rkhunter –cronjob –report-warnings-only
) | /bin/mail -s ‘rkhunter Daily Run (PutYourServerNameHere)’ [email protected]
chmod +x /etc/cron.daily/rkhunter.sh

3.) APF or CSF – A policy based iptables firewall system used for the easy configuration of iptables rules.
APF or CSF – A policy based iptables firewall system used for the easy configuration of iptables rules.

cd /usr/local/src
wget http://www.configserver.com/free/csf.tgz
tar -xzf csf.tgz
cd csf
sh install.sh
echo "CSF successfully installed!"
When your configuration is complete, you need to set the following in /etc/csf/csf.conf to disable “TESTING” mode and enable your firewall:

csf -r

cd /usr/local
wget http://www.rfxnetworks.com/downloads/apf-current.tar.gz
tar -xvzf apf-current.tar.gz
cd apf*

in config file

Change the value of USE_AD to

Change the Value of DEVEL_MODE to

Save and quit.
chkconfig –del apf
apf -s
If there are no issues and the firewall gets flushed every five minutes,
You can get into the conf file and edit the value of
that is, change it to


4.) Brute Force Detection – BFD is a shell script for parsing applicable logs and checking for authentication failures and blocks the attackers ip in the firewall

cd /usr/local/src
wget http://www.rfxn.com/downloads/bfd-current.tar.gz
tar -xvzf bfd-current.tar.gz
cd bfd*

echo -e "Please enter your email:"
read email
echo "You entered: $email"
echo "ALERT_USR="1"" >> /usr/local/bfd/conf.bfd
echo "EMAIL_USR="$email"" >> /usr/local/bfd/conf.bfd
echo "Brute Force Detection has been installed!"
echo "Email would be sent to $email"
/usr/local/sbin/bfd -s

5.) SSH Securing – For a better security of ssh connections.
Disabling Root Login and changing the listening port .

1.create a user for ssh like sshadminz
2.give the user wheel privilage through Whm
3.in /etc/ssh/sshd_config change the entry PermitRootLogin to no
4.in /etc/ssh/sshd_config change the entry #Port to Port xxxx (needed port,make sure that port is open in csf/iprules)
5.restart the sshd service

>ssh sshadmin@***.***.***.*** -p xxxx

Setting an SSH Legal Message         

The message is contained within the following file: /etc/motd

ALERT! You are entering a secured area! Your IP and login information
have been recorded. System administration has been notified.

This system is restricted to authorized access only. All activities on
this system are recorded and logged. Unauthorized access will be fully
investigated and reported to the appropriate law enforcement agencies.

6.) Host.conf Hardening –Prevents IP spoofing and dns poisoning

The host.conf file resides in /etc/host.conf.
order bind,hosts
multi on
nospoof on

7.) Sysctl.conf Hardening – Prevents syn-flood attacks and other network abuses.
#Kernel sysctl configuration file for Red Hat Linux
# For binary values, 0 is disabled, 1 is enabled. See sysctl(8) and
# sysctl.conf(5) for more details.

# Disables packet forwarding

# Disables IP source routing
net.ipv4.conf.all.accept_source_route = 0
net.ipv4.conf.lo.accept_source_route = 0
net.ipv4.conf.eth0.accept_source_route = 0
net.ipv4.conf.default.accept_source_route = 0

# Enable IP spoofing protection, turn on source route verification
net.ipv4.conf.all.rp_filter = 1
net.ipv4.conf.lo.rp_filter = 1
net.ipv4.conf.eth0.rp_filter = 1
net.ipv4.conf.default.rp_filter = 1

# Disable ICMP Redirect Acceptance
net.ipv4.conf.all.accept_redirects = 0
net.ipv4.conf.lo.accept_redirects = 0
net.ipv4.conf.eth0.accept_redirects = 0
net.ipv4.conf.default.accept_redirects = 0

# Enable Log Spoofed Packets, Source Routed Packets, Redirect Packets
net.ipv4.conf.all.log_martians = 0
net.ipv4.conf.lo.log_martians = 0
net.ipv4.conf.eth0.log_martians = 0

# Disables IP source routing
net.ipv4.conf.all.accept_source_route = 0
net.ipv4.conf.lo.accept_source_route = 0
net.ipv4.conf.eth0.accept_source_route = 0
net.ipv4.conf.default.accept_source_route = 0

# Enable IP spoofing protection, turn on source route verification
net.ipv4.conf.all.rp_filter = 1
net.ipv4.conf.lo.rp_filter = 1
net.ipv4.conf.eth0.rp_filter = 1
net.ipv4.conf.default.rp_filter = 1

# Disable ICMP Redirect Acceptance
net.ipv4.conf.all.accept_redirects = 0
net.ipv4.conf.lo.accept_redirects = 0
net.ipv4.conf.eth0.accept_redirects = 0
net.ipv4.conf.default.accept_redirects = 0

# Disables the magic-sysrq key
kernel.sysrq = 0

# Decrease the time default value for tcp_fin_timeout connection
net.ipv4.tcp_fin_timeout = 15

# Decrease the time default value for tcp_keepalive_time connection
net.ipv4.tcp_keepalive_time = 1800

# Turn off the tcp_window_scaling
net.ipv4.tcp_window_scaling = 0

# Turn off the tcp_sack
net.ipv4.tcp_sack = 0

# Turn off the tcp_timestamps
net.ipv4.tcp_timestamps = 0

# Enable TCP SYN Cookie Protection
net.ipv4.tcp_syncookies = 1

# Enable ignoring broadcasts request
net.ipv4.icmp_echo_ignore_broadcasts = 1

# Enable bad error message Protection
net.ipv4.icmp_ignore_bogus_error_responses = 1

# Log Spoofed Packets, Source Routed Packets, Redirect Packets
net.ipv4.conf.all.log_martians = 1

# Increases the size of the socket queue (effectively, q0).
net.ipv4.tcp_max_syn_backlog = 1024

# Increase the tcp-time-wait buckets pool size
net.ipv4.tcp_max_tw_buckets = 1440000

# Allowed local port range
net.ipv4.ip_local_port_range = 16384 65536

# Turn on execshield

After you make the changes to the file you need to run /sbin/sysctl -p and sysctl -w net.ipv4.route.flush=1 to enable the changes without a reboot.

The rules were taken from: http://ipsysctl-tutorial.frozentux.net/ ... orial.html

8.) FTP Hardening – Secure FTP software by upgrading to latest version

FTP: In WHM >> Service Configuration, there is an option to change 2 settings for FTP. By default
the first will be set to use pure-ftpd (this is good) and
the second is to allow anonymous FTP (this is very bad).
turn anonymous OFF.
How many FTP logons you allow each account in your Feature Lists. Up to 3 is fine - anything over 10 is getting silly and simply invites your users to use your server for file sharing.
“Hardening Pure/Proftpd”
cp -p /etc/pure-ftpd.conf /etc/pure-ftpd.conf.bk
vi /etc/pure-ftpd.conf
AnonymousOnly no
NoAnonymous yes
PassivePortRange 30000 30050 ----- Please open 30000:30050 in the /etc/csf/csf.conf after the harden the FTP.

9.)TMP Hardening – Hardening

10.) Secure and Optimize Apache – Tweak apache for a better performance, stability and security.

[root@host /] vim /etc/httpd/conf/httpd.conf
This list is a composite of the settings we will be reviewing from fresh install on a cPanel server:

OR AT WHM Home » Service Configuration » Apache Configuration
MinSpareServers 5
MaxSpareServers 10
ServerLimit 600
MaxClients 600
MaxRequestsPerChild 0
KeepAlive On
MaxKeepAliveRequests 100
KeepAliveTimeout 3
Timeout 30

Timeout 300
Usually this value doesn’t require editing and a default of 300 is sufficient. Lowering the ‘Timeout’ value will cause a long running script to terminate earlier than expected.
On virtualized servers like VPS servers, lowering this value to 100 can help improve performance.
KeepAlive On
This setting should be “On” unless the server is getting requests from hundreds of IPs at once.
High volume and/or load balanced servers should have this setting disabled (Off) to increase connection throughput.
MaxKeepAliveRequests 100
This setting limits the number of requests allowed per persistent connection when KeepAlive is on. If it is set to 0, unlimited requests will be allowed.
It is recommended to keep this value at 100 for virtualized accounts like VPS accounts. On dedicated servers it is recommended that this value be modified to 150.
KeepAliveTimeout 15
The number of seconds Apache will wait for another request before closing the connection. Setting this to a high value may cause performance problems in heavily loaded servers. The higher the timeout, the more server processes will be kept occupied waiting on connections with idle clients.
It is recommended that this value be lowered to 5 on all servers.
MinSpareServers 5
This directive sets the desired minimum number of idle child server processes. An idle process is one which is not handling a request. If there are fewer spareservers idle then specified by this value, then the parent process creates new children at a maximum rate of 1 per second. Setting this parameter to a large number is almost always a bad idea.
Liquidweb recommends adjusting the value for this setting to the following:
Virtualized server, ie VPS 5
Dedicated server with 1-2GB RAM 10
Dedicated server with 2-4GB RAM 20
Dedicated server with 4+ GB RAM 25

11.)WHM Tweaking – Tweak WHM for better security and performance.

Server Setup =>> Tweak Settings
Check the following items...
Under Domains: Prevent users from parking/adding on common internet domains. (ie hotmail.com, aol.com)
Under Mail: Attempt to prevent pop3 connection floods
Default catch-all/default address behavior for new accounts - blackhole

Goto Server Setup =>> Tweak Security
Enable php open_basedir Protection

12.) PHP Tightening – Tweak PHP by changing

Edit php.ini as per need

[root@server ]# nano /usr/local/lib/php.ini
Safe_mode = On
allow_url_fopen = off
expose_php = Off
Enable_dl= Off
magic_quotes = On
register_globals = off
display errors = off
disable_functions = system, show_source, symlink, exec, shell_exec, passthru, phpinfo, popen, proc_open

13.)PHP Upgarde – Compile PHP to its latest stable version which increases server security.


14.)Shell Fork Bomb/Memory Hog Protection

Home » Security Center » Shell Fork Bomb Protection

15.)ClamAV – Is a cross-platform antivirus software tool-kit able to detect many types of malicious software, including viruses
Main >> cPanel >> Manage Plugins
* Install clamav
Tick ClamAV

cd /usr/local/src/

#wget http://sourceforge.net/projects/clamav/ ... z/download

wget http://ncu.dl.sourceforge.net/project/c ... 8.1.tar.gz

wget http://sourceforge.net/projects/clamav/ ... t/download

#clam latest
wget http://kaz.dl.sourceforge.net/project/c ... 8.3.tar.gz

tar -zxvf clamav-0.98.1.tar.gz

cd clamav-0.98.1

useradd clamav



make install


yum install zlib zlib-devel
* Run the scan
[root@server ]# clamscan -r /home
In WHM -> Plugins -> ClamAV Connector, ensure that "Scan Mail" is checked.

clamscan -ir / -l clamscanreport

15.)System Integrity Monitor – Service monitoring of HTTP, FTP, DNS, SSH, MYSQL & more

cd /usr/src/
wget http://www.rfxn.com/downloads/sim-current.tar.gz
tar zxf sim-current.tar.gz
cd sim-3*
./setup -i
perl -pi -e "s/^init.named.*/init.named on/" /usr/local/sim/config/mods.control
perl -pi -e "s/^init.httpd.*/init.httpd on/" /usr/local/sim/config/mods.control
perl -pi -e "s/^init.mysqld.*/init.mysql on/" /usr/local/sim/config/mods.control
perl -pi -e "s/^init.named.*/init.named on/" /usr/local/sim/config/mods.control
perl -pi -e "s/^init.exim.*/init.exim on/" /usr/local/sim/config/mods.control
sim -j

16.)SPRI – Tool for changing the priority of different processess running in the server according to the level of importance and thereby increasing the performance and productivity of the server.

cd /usr/src
wget http://www.rfxn.com/downloads/spri-current.tar.gz
tar zxvf spri-current.tar.gz
cd spri-0*
spri -v

17.)MySQL optimization – Optimize MySQL value for better performance and stability

max_connections = 400
key_buffer = 16M
myisam_sort_buffer_size = 32M
join_buffer_size = 1M
read_buffer_size = 1M
sort_buffer_size = 2M
table_cache = 1024
thread_cache_size = 286
interactive_timeout = 25
wait_timeout = 1000
connect_timeout = 10
max_allowed_packet = 16M
max_connect_errors = 10
query_cache_limit = 1M
query_cache_size = 16M
query_cache_type = 1
tmp_table_size = 16M

open_files_limit = 8192

max_allowed_packet = 16M

key_buffer = 32M
sort_buffer = 32M
read_buffer = 16M
write_buffer = 16M

MySQL parameters like query_cache_size, key_buffer_size, Table_cache, sort_buffer, read_rnd_buffer_size, thread_cache, tmp_table_size, query_cache_size etc should be altered according to your server status.

18.)Root Loger

Root Login Email alert
2. cd /root
3. vi .bashrc
4. Scroll to the end of the file then add the following:
echo ‘ALERT – Root Shell Access (YourserverName) on:’ `date` `who` | mail -s “Alert:
Root Access from `who | cut -d’(‘ -f2 | cut -d’)’ -f1`” [email protected]
Replace YourServerName with the handle for your actual server
Replace [email protected] with your actual email address

19.)MyTOP – A console-based (non-gui) tool for monitoring the threads and overall performance of a MySQL

/scripts/realperlinstaller –force Getopt::Long
/scripts/realperlinstaller –force DBI
/scripts/realperlinstaller –force DBD::mysql
/scripts/realperlinstaller –force Term::ReadKey

wget http://jeremy.zawodny.com/mysql/mytop/mytop-1.6.tar.gz
tar zxpfv mytop-1.6.tar.gz
cd mytop-1.6
perl Makefile.PL && make && make install

Error in option spec: “long|!” error message if you are trying to execute the mytop command. Please do the following to solve this error.
After doing perl Makefile.PL edit the mytop script inside the installation location and Search for the line
“long|!” => \$config{long_nums},
and comment it to
#”long|!” => \$config{long_nums},
and then execute make install from the source directory to install the altered mytop script.

After installing mytop you need to create a new file under /root/.mytop (mytop config file for root) with the lines below (mysql root password is found on /root/.my.cnf:

mytop -d mysql

20.)MultiTail – MultiTail is a program for monitoring multiple log files, in the fashion of the original tail program
cd /usr/src/
wget http://www.vanheusden.com/multitail/multitail-6.2.1.tgz
tar zxvf multitail-6.2.1.tgz
cd multitail-*
yum install ncurses ncurses-devel -y
make install
multitail -i /etc/host.conf -i /etc/sysctl.conf

21.)Mod_Security – ModSecurity is an embeddable web application firewall.

To install mod_security, go to WHM => EasyApache (or alternatively via CLI, run /scripts/easyapache). After you select your Apache and PHP versions,
you’ll be brought to the Short Options page. Select mod_security from the list, then proceed with the build.

Once compiled and installed Please use following URL for the Mod Security rules install in Cpanel
ConfigServer ModSecurity Control provides an easy way of monitoring which rules are being triggered on the server in real time but more importantly, you can whitelist certain rules either globally accross the entire server or on a per account/domain basis if some of the rules conflict with a particular script or functionality (e.g. FrontPage). To install CMC, run the following:

rm -fv cmc.tgz

wget http://www.configserver.com/free/cmc.tgz
tar -xzf cmc.tgz
cd cmc
sh install.sh
cd ..
rm -Rfv cmc/ cmc.tgz

If you log in to WHM you will now see “ConfigServer ModSec Control” under “Plugins”. It’s important that you click on it because when it’s run the first time, it will create the file “modsec2.whitelist.conf” if it doesn’t already exist. If that file doesn’t exist then you’ll find Apache won’t start when we come to the end of this guide. Also while you’re here, click on “Disable modsecparse.pl”. This will disable the cPanel cron job that processes and empties the mod_security log, allowing you to use the log watching tool built in to CMC.

As to help our VPS and Dedicated Server customers who might also be effected by this we have designed the following guide to make installing Atmoic Mod Security into cPanel with little to no fuss.

Stage 1: Run the following commands at command line:

mkdir /var/asl
mkdir /var/asl/tmp
mkdir /var/asl/data
mkdir /var/asl/data/msa
mkdir /var/asl/data/audit
mkdir /var/asl/data/suspicious
chown nobody.nobody /var/asl/data/msa
chown nobody.nobody /var/asl/data/audit
chown nobody.nobody /var/asl/data/suspicious
chmod o-rx -R /var/asl/data/*
chmod ug+rwx -R /var/asl/data/*
mkdir /var/asl/updates
mkdir /var/asl/rules/
mkdir /var/asl/rules/clamav
mkdir /etc/asl/
touch /etc/asl/whitelist
cd /usr/local/src/
wget http://updates.atomicorp.com/channels/r ... est.tar.gz


wget https://dl.dropboxusercontent.com/u/305 ... %29.tar.gz

tar zxvf modsec-2.7-free-latest.tar.gz
mkdir /usr/local/apache/conf/modsec_rules/
cp modsec/* /usr/local/apache/conf/modsec_rules/

These command will create the required directory’s and download the latest free version of the Atomic Mod Security rules. It will also directly install them into the location of Apache designed for cPanel and configure the permission.

Stage 2: Configure cPanel to use the Mod Security Rules

In this stage, you can do everything from WHM as long as you have Mod Security already installed as part of your EasyApache build. If you do not, you will need to rebuild apache with Mod Security.

In go to: WHM -> Plugins -> Mod Security and then click: Edit Config

In this section, delete all the current content and then paste in the following configuration:

SecRequestBodyAccess On
SecAuditLogType Concurrent
SecResponseBodyAccess On
SecResponseBodyMimeType (null) text/html text/plain text/xml
SecResponseBodyLimit 2621440
SecAuditLogRelevantStatus "^(?:5|4(?!04))"
SecServerSignature Apache
SecUploadDir /var/asl/data/suspicious
SecUploadKeepFiles Off
SecAuditLogParts ABIFHZ
SecArgumentSeparator "&"
SecCookieFormat 0
SecRequestBodyInMemoryLimit 131072
SecDataDir /var/asl/data/msa
SecTmpDir /tmp
SecAuditLogStorageDir /var/asl/data/audit
SecResponseBodyLimitAction ProcessPartial

Include /usr/local/apache/conf/modsec_rules/10_asl_antimalware.conf
Include /usr/local/apache/conf/modsec_rules/10_asl_rules.conf
Include /usr/local/apache/conf/modsec_rules/20_asl_useragents.conf
Include /usr/local/apache/conf/modsec_rules/30_asl_antispam.conf
Include /usr/local/apache/conf/modsec_rules/50_asl_rootkits.conf
Include /usr/local/apache/conf/modsec_rules/60_asl_recons.conf
Include /usr/local/apache/conf/modsec_rules/99_asl_jitp.conf
Include /usr/local/apache/conf/modsec2.whitelist.conf
Save this and restart Apache.
touch /usr/local/apache/conf/modsec2.whitelist.conf
This should now have successfully installed the Atomic mod security rules into cPanel which are a much more secure rule base and include extra protection which is important for the latest hacks.




Once with out Any Panel

When the build is done, mod_security will be installed. The files are kept in the following location:

Mod Security once installed, provides some default rules. The file with the rules resides under /usr/local/apache/conf/
The file modsec2.user.conf.default contains the rules which should be copied over to modsec2.user.conf.

cp -p modsec2.user.conf.default modsec2.user.conf

Restart the httpd service once.
http://www.modsecurity.org/documentatio ... mples.html
mod_security rules
When hack attempts are identified by mod_security, they are logged in /usr/local/apache/logs/audit_log with the IP of the offender and what rule was violated.
Visitors that trigger mod_security rules are greeted with a “406: Not Acceptable” error when doing so.
However, mod_security does occasionally block legitimate website access attempts,
specifically for software that happens to make calls consistent with a specific rule that mod_security is configured to block.
Therefore, you may wish to either disable that rule, or disable mod_security for a specific domain or part of your website.
Doing this is rather easy from command line.

First, open up your httpd.conf (/usr/local/apache/conf/httpd.conf) and locate your domain’s block.
Under it you’ll see a line like this that is commented out:
# Include "/usr/local/apache/conf/userdata/std/2/$user/$domain/*.conf"
Uncomment this line, then create the folder indicated (note that $user is your username, and $domain is your domain name):
mkdir -p /usr/local/apache/conf/userdata/std/2/$user/$domain/
cd /usr/local/apache/conf/userdata/std/2/$user/$domain/
Create a file called modsec.conf, and insert this line:
SecRuleEngine Off
To apply, restart Apache
Disabling Mod-Security for a single account
To disable the mod_security for a particular account, just add the following in the users .htaccess file
SecFilterEngine Off
SecFilterScanPOST Off

If mod_security2

SecRuleEngine Off

22.)Mod_Evasive – mod_evasive is an evasive maneuvers module for Apache that provides evasive action in the
event of an HTTP DoS 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 more.

Download the latest source file from http://www.zdziarski.com
cd /usr/local/src/
wget http://pkgs.fedoraproject.org/repo/pkgs ... 0.1.tar.gz
wget http://www.zdziarski.com/projects/mod_e ... 0.1.tar.gz
tar -xvzf mod_evasive_1.10.1.tar.gz
cd mod_evasive/

We also have cPanel running on this box, so, to install, we run the following:

/usr/local/apache/bin/apxs -i -a -c mod_evasive20.c

Now, that will create an entry in the httpd.conf file, and, if we want to retain that after an upgrade/rebuild, we need to tell cPanel not to take it out! Do do this, we now run this:

/usr/local/cpanel/bin/apache_conf_distiller –update

Now, to change the settings for mod_evasive, we need to add them in some place. All we have done so far, is install the actually module into apache, and, even with a restart, it would not be using it. So, I like to add things into my includes files through either WHM, or, directly through the terminal. To do this, we run the following:

vim /usr/local/apache/conf/includes/post_virtualhost_2.conf

Once the file is open, lets add in the following lines to the bottom of the file:

DOSHashTableSize 3097
DOSPageCount 2
DOSSiteCount 50
DOSPageInterval 1
DOSSiteInterval 1
DOSBlockingPeriod 10
<IfModule mod_evasive20.c>
DOSHashTableSize 3097
DOSPageCount 2
DOSSiteCount 50
DOSPageInterval 1
DOSSiteInterval 1
DOSBlockingPeriod 10

23.)Maldetect -

cd /usr/local/src
wget http://www.rfxn.com/downloads/maldetect-current.tar.gz
tar -xzvf maldetect-current.tar.gz
cd maldetect-*
sh install.sh
cd ..

To run the maldet

>maldet -a /

You are almost done :)

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