Smith is an agent of an unknown branch of the government. He was once saved by Venom and Wolverine, and would arrange for Venom's prison pardon. When Venom and Wolverine teamed up to take down the mutant known as Dirt Nap and the inter-dimensional villainous Chimera, they rescued a Government agent who identified himself only as Smith, the agent seemed appreciative of the two heroes help but Venom in particular would find out just how much influance Smith had first hand.
After his trial for the murder of a New York police officer Eddie Brock was found guilty despite the best efforts of Matt Murdoch, and that's when an offer that seemed too good to be true was given to him by Smith, work for the government and all charges would be dropped, Eddie of course accepted and as part of the deal submitted to surgery, having a thermal bomb implanted in his chest. Eddie worked several jobs for the government but eventually the symbiote figured out how to defuse the bomb and Eddie went AWOL.
Smith then tricked Spider-Man into luring Venom into a sonic trap that was to Peter's knowledge non-lethal, but Smith tricked Peter, and after Venom was caught in the trap it seemed the symbiote and Eddie were both killed, but as time would tell appearances can be deceiving....
At the end of Onslaught story arc, he appears as SHIELD agent at Hulkbuster base in Nevada. He describes him as the best mutant hunter in the agency. Due to his psychic barriers was responsible for the "death" of Nina, the manite Child. But instead he saved and allowed her to escape.