Basics

APF is a policy based iptables firewall system designed for ease of use and configuration. It employs a subset of features to satisfy the veteran Linux user and the novice alike. Packaged in tar.gz format and RPM formats, make APF ideal for deployment in many server environments based on Linux. APF is developed and maintained by R-fx Networks: http://www.rfxnetworks.com/apf.php

This guide will show you how to install and configure APF firewall, one of the better known Linux firewalls available.10

Requirements:
– Root SSH access to your server

Lets begin!
Login to your server through SSH and su to the root user.

cd /root/downloads or another temporary folder where you store your files.

2. wget http://www.rfxnetworks.com/downloads/apf-current.tar.gz

3. tar -xvzf apf-current.tar.gz

4. cd  apf-9.6-5/ or whatever the latest version is.

5. Run the install file: ./install.sh
You will receive a message saying it has been installed

Installing APF 9.6-5: Completed.
Installation Details:
Install path:         /etc/apf/
Config path:          /etc/apf/conf.apf
Executable path:      /usr/local/sbin/apf
Other Details
Listening TCP ports: 53,2086,2087,3306
Listening UDP ports: 53,39437
Note: These ports are not auto-configured; they are simply presented for information purposes. You must manually configure all port options.

6. Lets configure the firewall: nano -w /etc/apf/conf.apf
We will go over the general configuration to get your firewall running. This isn’t a complete detailed guide of every feature the firewall has. Look through the README and the configuration for an explanation of each feature.

We like to use DShield.org’s “block” list of top networks that have exhibited
suspicious activity.
FIND: USE_DS="0"
CHANGE TO: USE_DS="1"

7. Configuring Firewall Ports:

Cpanel Servers
We like to use the following on our Cpanel Servers

Common ingress (inbound) ports
# Common ingress (inbound) TCP ports -3000_3500 = passive port range for Pure FTPD
IG_TCP_CPORTS="21,22,25,53,80,110,143,443,2082,2083, 2086,2087, 2095, 2096,3000_3500"
#
# Common ingress (inbound) UDP ports
IG_UDP_CPORTS="53"

Common egress (outbound) ports
# Egress filtering [0 = Disabled / 1 = Enabled]
EGF="1"

# Common egress (outbound) TCP ports
EG_TCP_CPORTS="21,25,80,443,43,2089"
#
# Common egress (outbound) UDP ports
EG_UDP_CPORTS="20,21,53"

Ensim Servers
We have found the following can be used on Ensim Servers – although we have not tried these ourselves as I don’t run Ensim boxes.

Common ingress (inbound) ports
# Common ingress (inbound) TCP ports
IG_TCP_CPORTS="21,22,25,53,80,110,143,443,19638"
#
# Common ingress (inbound) UDP ports
IG_UDP_CPORTS="53"

Common egress (outbound) ports
# Egress filtering [0 = Disabled / 1 = Enabled]
EGF="1"

# Common egress (outbound) TCP ports
EG_TCP_CPORTS="21,25,80,443,43"
#
# Common egress (outbound) UDP ports
EG_UDP_CPORTS="20,21,53"

Save the changes: Ctrl+X then Y

8. Starting the firewall
/usr/local/sbin/apf -s

Other commands:
usage ./apf [OPTION]
-s|--start ......................... load firewall policies
-r|--restart ....................... flush & load firewall
-f|--flush|--stop .................. flush firewall
-l|--list .......................... list chain rules
-st|--status ....................... firewall status
-a HOST CMT|--allow HOST COMMENT ... add host (IP/FQDN) to allow_hosts.rules and
immediately load new rule into firewall
-d HOST CMT|--deny HOST COMMENT .... add host (IP/FQDN) to deny_hosts.rules and
immediately load new rule into firewall

9. After everything is fine, change the DEV option
Stop the firewall from automatically clearing itself every 5 minutes from cron.
We recommend changing this back to “0” after you’ve had a chance to ensure everything is working well and tested the server out.

nano -w /etc/apf/conf.apf

FIND: DEVM="1"
CHANGE TO: DEVM="0"

10. Checking the APF Log

Will show any changes to allow and deny hosts among other things.
tail -f /var/log/apf_log