SAN FRANCISCO - A former Uber security specialist accused the company of dispatching spies to steal its rivals' trade secrets and using shady tactics to thwart its competition in the ride-hailing market, according an inflammatory letter unsealed Friday by a federal judge. Those tactics allegedly included impersonating other people, illegally recording conversations and hacking into computers. Former Uber manager Richard Jacobs, who was fired this year, made the claims in a 37-page letter that sought a big payoff for being forced out.