GEN:SID 1:2449
Message FTP ALLO overflow attempt
Summary This event is generated when an attempt is made to exploit a buffer
overflow vulnerability associated with Ipswitch WS FTP ALLO command.
Impact Remote access.  A successful attack may permit the remote execution of
arbitrary commands with system privileges. A Denial of Service (DoS)
attack may also be possible.
Detailed Information Ipswitch WS FTP is an FTP server. A vulnerability exists with the ALLO
command that can cause a buffer overflow and permit the execution of
arbitrary commands with system privileges. The buffer overflow can be
caused by supplying an overly long argument to the ALLO command.
Affected Systems Ipswitch WS FTP Server 1.0.1 through 1.0.5, 2.0 through 2.0.4,
    3.0 1, 3.0, 3.1, 3.1.1, 3.1.2, 3.1.3, 3.4, 4.0 2, 4.0 1 and 4.0
    Ipswitch WS_FTP Pro 6.0, 7.5, 8.0 3, 8.0 2
Attack Scenarios An attacker can use one of the publicly available exploit scripts to
cause the overflow to occur.
Ease of Attack Simple.  Many exploits exist.
Corrective Action Upgrade to the latest non-affected version of the software.

Use scp as an alternative to ftp

Disallow ftp access to internal resources from external sources
Additional References  
Rule References bugtraq: 9953