It indicates an attacker attempted a Denial of Service attack against WTFTP Pro FTP server. WFTPD Pro is vulnerable to a denial of service attack, caused by a a programming error when handling MLST (MultiLocus Sequence Typing) commands. An authenticated attacker could issue a long MLST command to the FTP server to cause the server to crash.
Texas Imperial Software WFTPD Pro 3.21, R3, R2, and R1.
Denial of Service
Apply appropriate patch from the vendor or Upgrade to non-vulnerable version if available.