Two men accused of conspiring to break into an Army computer network and the phone system surrendered Tuesday in federal court, but the man the government says was the ringleader remained at large. Silicon Valley computer experts Mark K. Lottor, 25, and Robert E. Gilligan, 31, turned themselves over to authorities before U.S. District Court Magistrate Patricia Trumbull. Lottor and Gilligan entered innocent pleas and were released on $100,000 bond each. They are to return to court next week. Lottor faces five courts and Gilligan six in the government's 19-count indictment alleging a scheme to steal military secrets and phone numbers from the FBI investigation of former Philippine President Ferdinand Marcos. Authorities were still searching Tuesday for 24-year-old Kevin L. Poulsen, who is charged in 16 counts. Poulsen faces up to 37 years in prison if convicted. The other two suspects face 20 years each if found guilty of all charges. Lottor works for SRI International and Gilligan works for Sun Microsystems of Mountain View. Poulsen, a former SRI worker who is believed to have fled to Los Angeles after leaving a job with Sun, was an unindicted co-conspirator in the 1984 computer break-in case at the University of California at Los Angeles. Poulsen's friend, hacker Ron Austin, was convicted on charges related to the break-in. Authorities said Poulsen used the computer handle ``Dark Dante'' at the time. Federal officials contend the latest computer tampering began in 1985 and started to fall apart in February 1988 when police found telephone equipment belonging to Pacific Bell in a storage locker rented by Poulsen. ``As far as techniques, you can see this started out as a burglary,'' said FBI Agent William Smith. ``That's what we have: burglars who came upon equipment that allowed them to go beyond the common crime of burglary.''