ListLib prevents the LISTNER from supporting a DoS attack.

ListLib is a ShareWare product from GreenHouse. It prevents a Denial of Service (DoS) attack through the FTP port: A possible attacker can use his FTP client to start as many FTPSERV processes on the Tandem system, until the number of processes, or swap space, or other resources, are exhausted, and no further service is granted.FunctionThe tool is designed as a library, which becomes part of the LISTNER product on the Tandem system. It intercepts the Process_Create_ procedure call and, before the call is executes, it checks the number of already running FTPSERV processes. In case the found number of processes exceeds the number of configured ones, no new FTPSERV process is created. The library prevents an uncontrolled start of FTPSERV processes.
It as well controls the EXCHO server: Up to two ECHO services can be used in parallel per IP stack, any additional request is rejected.

1500 US$ per NSK system for international users
1000 EURO per NSK system for European users

For detail information please read the documentation.

In case you find a bug, please let me know, and I'll fix it.

GreenHouse Software & Consulting
Carl Weber