Merwall is a lightweight Linux firewall, built as Loadable Kernel Module and a userspace administration tool.

It is based on the Netfilter API for packet filtering and rule matching. Sysfs virtual filesystem is used for communication between userspace and kernelspace.

$ make
$ sudo insmod kmerwall.ko

$ sudo rmmod kmerwall
$ make clean

• Drop all UDP traffic:
• ./merwall_admin --proto UDP
• Drop all UDP traffic to/from port 53.
• ./merwall_admin --proto UDP --dstport 53
• Allow all TCP traffic coming from 1.2.3.4:80
• ./merwall_admin --action PASS --proto TCP --direction IN --srcip 1.2.3.4 --srcport 80
• Allow outgoing traffic to port 80
• ./merwall_admin --action PASS --dstport 80
• Delete rule number 33
• ./merwall_admin --delete 33
• List all rules.
• ./merwall_admin --list

Update documentation: Installation, usage etc.,

• Thanks to Djalal "tixxdz" Harouni ( http://opendz.org/ ) for all the tips, help and encouragement.