TCP/IP Connection Cutting On Linux Firewalls

Chris Lowth writes "Network security administrators sometimes need to be able to abort TCP/IP connections routed over their firewalls on demand. This would allow them to terminate connections such as SSH tunnels or VPNs left in place by employees over night, abort hacker attacks when they are detected, stop high bandwidth consuming downloads - etc. There are many potential applications. This article describes how a Linux IPTables based firewall/router can be used to send the right combination of TCP/IP packets to both ends of a connection to cause them to abort the conversation. It describes the steps required to perform this task, and introduces a new open-source utility called 'cutter' that automates the process."

Comments

great

[mike_scheck]

So now I don't just have to worry about losing my vpn into work in the middle of the night because of some unavoidable packet loss, but also because of some automagic utility that people will throw into place for my benefit. Will the "features" never stop?

Re:great

[ColdGrits]

Or we just employ proper secutiry procedures, rather than relying upon a script running twice a day to kill off connections (let's face it, the original suggestion, namely run this twice a day, is pointless - the intruder woudl already have been in, done whatever they were doing, and gone long before the script dropped their connection. Yes, you'd have a nice shiny log to say "J00 waz 0wn3d", but it's a bit late by that point...

The actual killing of connections, now, THAT is a useful tool where your intrusion detection has detected an active intrusion (or intrusion attempt). But that's not what was being discussed in this subthread :)