FTP bounce attack

FTP bounce attack is an exploit of the FTP protocol whereby an attacker is able to use the PORT command to request access to ports indirectly through the use of the victim machine as a middle man for the request.

This technique can be used to port scan hosts discretely, and to access specific ports that the attacker cannot access through a direct connection.

nmap is a port scanner that can utilize an FTP bounce attack to scan other servers.

Nearly all modern FTP server programs are configured by default to refuse PORT commands that would connect to any host but the originating host, thwarting FTP bounce attacks.

See also

• Confused deputy problem

External links

• CERT Advisory on FTP Bounce Attack
• CERT Article on FTP Bounce Attack
• Original posting describing the attack