Killproc.exe is an executable program which can be found on randomly determined hosts by searching their file libraries. When used, it will attempt to stop rival processes on an adjacent host, with a 52.5% chance of success. It requires root to run.
On a host with killproc.exe available in the file list, you can use FTP to transfer it to other hosts. From there, you can run it and enter the name of an adjacent host and select a running process to attack it. If successful, the process will be stopped and killproc.exe can be run again immediately.
Rootkit.exe will always be assigned a process identifier, or PID, of 3.