Summary This indicates an intrusion attempt against the FTP service. Few machines are vulnerable to this attack.
Details
A "PORT" command is part of the FTP protocol and is usually not seen by the user, though the user will often see status messages like "PORT command successful". It tells the other side of the connection where to send data. It should be formatted as a comma-separated list of 6 numbers. Example:
PORT 192,0,2,63,4,01
This above example tells the other side to transfer data on 192.0.2.63, port 1025. If this command has been corrupted, then it is likely that an attacker is attempting to compromise the FTP service. However, since most FTP services are no longer vulnerable to this attack, it is unlikely that a compromise has actually occurred.
