The Finger Server Bug THE WORM WAS ABLE TO BREAK INTO MACHINES USING FINGER BECAUSE OF A BUG IN THE RELATIVELY SIMPLE FINGER SERVER. FINGER WAS AVAILABLE ON UNIX LONG BEFORE THE INTERNET. IT PROVIDED INFORMATION ABOUT USERS ON A SINGLE COMPUTER. THE UNIX NETWORK FINGER SERVER USES THE ORIGINAL SINGLE MACHINE FINGER PROGRAM. THE FINGER SERVER ACCEPTS A USER NAME SENT TO IT AT A STANDARD TCP PORT (79). THE SERVER THEN RUNS THE ORIGINAL FINGER PROGRAM. THE SERVER JUST SENDS THE OUTPUT OF THE FINGER PROGRAM BACK TO THE REMOTE MACHINE THROUGH THE NETWORK.

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This page is part of a section of lecture slides related to " The Internet Worm " within the topic "Computer Security: A Case Study?". Other slides within this section and other sections of slides for the topic "Computer Security: A Case Study?" can be accessed using the links below. Paranoia Raising Some Sample Security Problems The Internet Worm The Internet Worm What was "The Worm"? Finding Machine Names How the Worm Broke in Password Guessing The SENDMAIL "Trap Door" The Finger Server Bug Computer Memory Organization Computer Memory and Program Variables Memory Overflow The Finger Bug It Couldn't Happen Again! Could it?