(FORTUNE Magazine) – Paul Thayer, former chairman of LTV Corp., and Billy Bob Harris, a Dallas stockbroker, were sentenced to four years in prison and the maximum $5,000 fine for obstructing justice during the investigation of an insider trading case against them. The stiff sentences came a day after Thayer, former U.S. Deputy Secretary of Defense, agreed to pay $550,000, and Harris $275,000, to settle a civil suit with the Securities and Exchange Commission over insider trading. Thayer was charged with passing insider information in 1981 and 1982 about LTV and two companies he served as a director to Sandra Ryno, a woman with whom he had a ''close personal relationship,'' and to Harris. Federal attorneys have estimated that the scheme generated $3 million in illegal profits. U.S. District Court Judge Charles Richey was apparently not influenced by appeals from Thayer's attorneys that their client did not benefit personally from the scheme but was only trying to provide a nest egg for Ryno and her daughter. The SEC has concentrated its enforcement efforts on insider trading in recent years. Gary Lynch, the agency's director of enforcement, says about 20 criminal prosecutions for insider trading were started last year. ''The commission and the government are looking for highly visible cases,'' says Harvey Pitt, former chief counsel for the SEC. ''It helps create the illusion that the SEC is everywhere.''