Terms used for a computer system compromised in such a way that it opens a channel for a cracker. Typical back channel protocols are X-Windows System and shells such as telnet. Because these programs are often part of a target’s computer system, attacks that cannot otherwise compromise the system can nonetheless trigger a back connection that allows a remote shell. From a system security point of view, it is important to note that a back channel will contact the cracker, who must have a fixed IP Address. It is through this procedure that security sleuths can determine who the cracker is. This security sleuth information is known to those in the Computer Underground, so more sophisticated behavior is needed when introducing anonymizers in the back channel on previously compromised machines. Anonymizers are contacted by the back channel; they then forward the communication (maybe with further directions) to the attacker. Graham, R. Hacking Lexicon. [Online, 2001.] Robert Graham Website. http://www.linuxsecurity.com/resource_files/documentation/hacking-dict.html.