V.23 Softmodem for Asterisk with some Bildschirmtext-specific stuff in it. Pretends to be a modem but it actually sets up a telnet-like TCP session to an IP address. Like many things with Asterisk, you have to compile everything from source with this module in a particular location.
Daniel J. Berstein's homepage. There are tools and code galore here - check it out!
Cutter is a tool for linux-based firewalls that allows connections passing through them to be forcibly aborted by the firewall administrator.