In 1982, at age 15, as a high school student at Mt. Lebanon High School, Skrenta wrote the Elk Cloner virus that infected Apple II machines. It is widely believed to have been one of the first large-scale self-spreading personal computer viruses ever created.
In 1989, Skrenta started working on a multiplayer simulation game. In 1994, it was launched under the name Olympia as a pay-for-play PBEM game by Shadow Island Games.
Between 1991 and 1995, Skrenta worked at Unix System Labs and from 1996 to 1998 with IP-level encryption at Sun Microsystems. He later left Sun and became one of the founders of DMOZ. He stayed on board after the Netscape acquisition, and continued to work on the directory as well as Netscape Search, AOL Music, and AOL Shopping.
In 2015, Blekko, both the company and search engine, were acquired by IBM for their Watson computer system.
Skrenta was involved[when?][how?] in the development of VMS Monster an old MUD for VMS. VMS Monster was part of the inspiration for TinyMUD. He is also known for his role in developing TASS, an ancestor of tin, the popular threaded Usenet newsreader for Unix systems.