Rustock is a stealthy backdoor that provides the attacker with unauthorized remote access to the compromised computer. Although the parasite does not allow the intruder to control the infected PC, it converts the system to a hidden proxy used for certain malicious purposes, such as sending e-mail spam. Rustock uses an integrated rootkit to hide its registry entries, files and active processes. It is able to avoid detection by popular rootkit detectors and removers. Rustock runs as a service on every Windows startup.