The remote host is vulnerable to a Denial of Service (DoS) attack.
The remote host is running PlatinumFTP Server. The remote server is vulnerable to a remote Denial of Service (DoS) attack. Specifically, a remote user attempting to authenticate 50+ times with a user ID that includes '\\' will cause the server to fail. A successful attack would render the FTP server useless for valid users.
Upgrade to version 2.0 or higher.