Yeah, one of the things the Matrix gangs do heavily is Matrix vandalism. I suspect the tribes of little decker kiddie gangs took a hit in 2075 though with the new Matrix protocols. Fully functional Technomancers are just too rare to make lots of gangs out of (rarer even than Magicians) The Cereal Killers do vandalism, identity theft, blackmail and extortion, and just randomly be total fraggers to be people in the Matrix.
There's also really hardcore tech gangs, the Reality Hackers of Puyallup probaly being the most prominent. They specialize in Matrix theft and stealing and rebuilding tech. (Like chop shops with computers and electronics) They're also some of the best in the sprawl at physical intrusions when necessary to get at data.