Via PacketStorm :
WeBaCoo (Web Backdoor Cookie) is a web backdoor script-kit, aiming to provide a stealth terminal-like connection over HTTP between client and web server. It is a post exploitation tool capable to maintain access to a compromised web server. WeBaCoo was designed to operate under the radar of modern up-to-dated AV, NIDS, IPS, Network Firewalls and Application Firewalls, proving a stealth mechanism to execute system commands to the compromised server. The obfuscated communication is accomplished using HTTP header’s Cookie fields under valid client HTTP requests and relative web server’s responses.
Exemples sur le site officiel. Client codé en perl, backdoor en PHP.