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.