Modified Protocol droid
4-LOM's was originally programmed as a service droid on a luxury liner, but after some rogue malfunctioning 4-LOM turned to a life of thievery. Hearing of this, Jabba the Hutt modified 4-LOM further to become a bounty hunting droid which he then teamed up with another bounty hunter named Zuckuss. 4-LOM was one of several bounty hunters hired by Darth Vader to track down the Millennium Falcon.
Later after failing to capture Solo, 4-LOM attempted to steal the carbonite frozen Solo aboard the Slave I. Boba Fett thwarted the droid by putting a blaster bolt into his insectoid head.
4-LOM is an acronym (for the love of money). He was the only bounty hunter not mentioned in the novel adaptation of ESB, the mistaken identity on his action figure packaging was a continuing trend of being an afterthought.