GEN:SID 1:2391
Message FTP APPE overflow attempt
Summary This event is generated when an attempt is made to exploit a buffer
overflow vulnerability associated with WuFtpd APPE command.
Impact Remote access.  A successful attack may permit the remote execution of
arbitrary commands with system privileges.
Detailed Information WuFtpd is an FTP server based on BSD ftpd. A vulnerability exists
with the APPE 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 APPE
command.

The issue exists in the realpath() function. It is possible for an
attacker to send malformed data to the realpath() function that will
cause the overflow condition to occur.
Affected Systems Multiple systems using affected C libraries, libc
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

Recompile binaries statically linked to the system libc implementation
Additional References  
Rule References bugtraq: 8315
bugtraq: 8542
cve: 2000-0133
cve: 2003-0466