Not quite a self reproducing program and I did take down one of the UCSD servers one day. I was writing a shell script to do some complex and long running task. This was in the early days of the shell supporting functions. The script had a large number of functions and I named one of them to be the same name as the shell script. I set it in motion and logged out, as I knew it would take several hours to finish the work. The next day I logged in to find that the machine had the load spike as the shell script recursively started itself when it got to the function call that had the same name as the shell script. The admin kindly sent me a ‘top' output showing the load at several hundred and all the jobs having my name and being my shell script. Under this he wrote: “Never do this again.” I haven’t. David