The Mytob family is a big family of worms that can spread via email and via security vulnerabilities in the operating system. This is a general description of the family.

Mytob is loosely based on two other worm series: The Mydoom email worms and the SDBot/Spybot network worms. The SDBot series of worms is very common, but does not have email spreading. In addition, SDBots are rather plugin-based and easy to adjust to new technologies, so that they finally got equipped with email-spreading came as no surprise.

They appear to at least initially be spammed out from the author(s). New variants have occurred at a high frequency, with a regularity which looks almost scheduled.