Immediately after the Morris worm hit, somebody posted a patch to edit the sendmail binary, to keep it from switching into debug mode, and that was to patch the

Immediately after the Morris worm hit, somebody posted a patch to edit the sendmail binary, to keep it from switching into debug mode, and that was to patch the "DEBUG" command by replacing the "D" with a null. It certainly stopped the worm, but at what cost? Well in my usual day-to-day mailing list administration, I telnet'ed to sun.com 25 to validate some email addresses, and pressed return a couple time to clear out the telnet protocol negotiation characters. Then I EXPN'ed an email address, and it dumped out a shitload of debugging information! Turns out that "patch" to sendmail just turned the "DEBUG" command into the "" command, which I had entered by pressing return a few times at the beginning of the session! I reported it to postmaster@sun.com and they closed that particular hole. Lesson: Don't just blindly apply binary patches you see on the net to system programs, without thinking about them first.