Proxy is a firewall that blocks and re-creates a connection between two points. Proxy has an ability to hide a user from the outside world or an attacker from a user. For malicious purposes a proxy may be used to make a connection anonymous between an attacker and your computer, making the connection more difficult to notice. SMTP and FTP may be used in conjunction with Firewall Killers, Downloaders, RATs, and Trojans.