This indicates an attack attempt to exploit a Command Execution vulnerability in ProFTPd.
The vulnerability is a backdoor in ProFTPd ftp server. The backdoor is meant to be used for disaster recovery. It may allow remote attackers to execute commands on a vulnerable system by sending a crafted "help" command.
ProFTPd ftp server.
System Compromise: Remote attackers can gain control of vulnerable systems.
Currently we are not aware of any vendor supplied patch for this issue.