Block outgoing TCP connection to a given host or IP?

Question

Is it possible to intercept an outgoing TCP connection to a given host or IP in Windows and block that connection on the TCP level, i.e. at the connect(...) layer? Or prevent connection to a specific IP in the first place?

Or do I need to write a packet filter to intercept traffic to a certain address?

Answer 1

It's probably best to simply use the system's firewall API. On Windows: http://msdn.microsoft.com/en-us/library/aa366449(v=VS.85).aspx

Otherwise you are going to be writing drivers and such... complete hassle considering the functionality is built into the OS these days.

Answer 2

On linux? Configure iptables to drop the connection, perhaps.