GEN:SID 1:1621
Message FTP CMD overflow attempt
Summary This event is generated when activity relating to spurious ftp traffic is detected on the network.
Impact Varies from information gathering to a serious compromise of an ftp server.
Detailed Information FTP is used to transfer files between hosts. This event is indicative of spurious activity in FTP traffic between hosts.

The event may be the result of a transfer of a known protected file or it could be an attempt to compromise the FTP server by overflowing a buffer in the FTP daemon or service.
Affected Systems  
Attack Scenarios A user may transfer sensitive company information to an external party using FTP.

An attacker might utilize a vulnerability in an FTP daemon to gain access to a host, then upload a Trojan Horse program to gain control of that host.
Ease of Attack Simple.
Corrective Action Disallow access to FTP resources from hosts external to the protected network.

Use secure shell (ssh) to transfer files as a replacement for FTP.
Additional References