How to install CSF Firewall on your Server.
Installation
Installation is quite straightforward:
rm -fv csf.tgz
wget http://www.configserver.com/free/csf.tgz
tar -xzf csf.tgz
cd csf
sh install.sh
Next, test whether you have the required iptables modules:
Don’t worry if you cannot run all the features, so long as the script doesn’t report any FATAL errors
You should not run any other iptables firewall configuration script. For example, if you previously used APF+BFD you can remove the combination (which you will need to do if you have them installed otherwise they will conflict horribly):
sh /etc/csf/remove_apf_bfd.sh
That’s it. You can then configure csf and lfd by edit the files directly in /etc/csf/*, or on cPanel servers use the WHM UI
csf installation for cPanel is preconfigured to work on a cPanel server with all the standard cPanel ports open.
csf installation for DirectAdmin is preconfigured to work on a DirectAdmin server with all the standard DirectAdmin ports open.
csf auto-configures your SSH port on installation where it’s running on a non-standard port.
csf auto-whitelists your connected IP address where possible on installation.
You should ensure that kernel logging daemon (klogd) is enabled. Typically, VPS servers have this disabled and you should check /etc/init.d/syslog and make sure that any klogd lines are not commented out. If you change the file, remember to restart syslog.
Download the firewall script from : http://www.configserver.com/
Security - Install And Configure Advanced Policy Firewall (APF) On CentOS
From Advanced Policy Firewall’s website:
“Advanced Policy Firewall (APF) is an IPTables(Netfilter) based firewall system designed around the essential needs of today’s Linux servers. The configuration is designed to be very informative and easy to follow. The management on a day-to-day basis is conducted from the command line with the ‘apf’ command, which includes detailed usage information on all the features.”
Installation
Downloading and extracting.
wget http://www.rfxn.com/downloads/apf-current.tar.gz
tar -zxvf http://www.rfxn.com/downloads/apf-current.tar.gz
cd apf-9.7-1
and Run:
APF will display locations of it’s executable and configuration files as well as ports detected as being used.
Configuration
APF’s basic configuration file is /etc/apf/conf.apf
By default everything is locked and You have to configure APF to open ports You need to use.
DEVEL_MODE=”1″ - be sure to set this option to 1 until You’re satisfied with the settings.
SET_MONOKERN=”0″ - APF supports monolithic kernels.
IFACE_IN=”eth0″ and IFACE_OUT=”eth0″ - untrusted interfaces connected to the network, mostly the Internet.
Testing
Start APF:
We can use the following parameters:
-s - start APF
-r - restart APF
-f - stop APF
-l - list statistics
-st - status of APF
-a host - allow connections from “host”
-d host - deny connections from “host”
Advanced Policy Firewall - http://www.rfxn.com/projects/advanced-policy-firewall
SELinux Access Control
SELinux has 3 forms of access control:
Type Enforcement (TE): Type Enforcement is the primary mechanism of access control used in the targeted policy
Role-Based Access Control (RBAC): Based around SELinux users (not necessarily the same as the Linux user), but not used in the default targeted policy
Multi-Level Security (MLS): Not used and often hidden in the default targeted
policy.
How to Disable Telnet
TELNET server listens for incoming messages on port 23, and sends outgoing messages to port 23.
1. Login to your server through SSH and su to root.
2. Type pico /etc/xinetd.d/telnet
3. Look for the line: disable = no and replace with disable = yes
4. Now restart the inetd service: /etc/rc.d/init.d/xinetd restart
5. Turn off it through chkconfig as well because it can still start through that.
/sbin/chkconfig telnet off
6. Scan your server to ensure port 23 is closed.
Count the number of connections each IP makes
Use netstat command to calculate and count the number of connections each IP address makes to the server.
netstat -anp |grep ‘tcp\|udp’ | awk ‘{print $5}’ | cut -d: -f1 | sort | uniq -c | sort -n
netstat - Print network connections, routing tables, interface statistics, masquerade connections, and multicast memberships
