Morris Worm - Architecture of The Worm

Architecture of The Worm

According to its creator, the Morris worm was not written to cause damage, but to gauge the size of the Internet. However, the worm was released from MIT to disguise the fact that the worm originally came from Cornell. Additionally, the Morris worm worked by exploiting known vulnerabilities in Unix sendmail, finger, and rsh/rexec, as well as weak passwords. Due to reliance on rsh (normally disabled on untrusted networks) it should not succeed on a recent, properly configured system.

A supposedly unintended consequence of the code, however, caused it to be more damaging: a computer could be infected multiple times and each additional process would slow the machine down, eventually to the point of being unusable. This would have the same effect as a fork bomb and crash the computer. The main body of the worm could only infect DEC VAX machines running 4BSD, and Sun-3 systems. A portable C "grappling hook" component of the worm was used to pull over (download) the main body, and the grappling hook could run on other systems, loading them down and making them peripheral victims.