Assitch is a remote packetfilter analyzer, that detects in and OUT rules by doing ACK scanning. (It’s useless against state-full filters.) Assitch is 3 years old, but still useful for debugging filter rules.
You can download it from the following link: https://packetstormsecurity.com/files/download/23452/assitch-2.6.tgz
Source: https://packetstormsecurity.com/files/23452/assitch-2.6.tgz.html