UNDERNEWS: The daily news service of the Progressive Review, Washington's most unofficial source John M. Poindexter, the retired Navy admiral who was President Ronald Reagan's national security adviser, has returned to the Pentagon to direct a new agency that is developing technologies to give federal officials instant access to vast new surveillance and information- analysis systems . . . Mr. Poindexter, who is 65, was a controversial figure both for his role in the Iran-contra scandals and for his efforts to assert military influence over commercial computer security technologies. With Oliver L. North, a former National Security Council aide, Mr. Poindexter was convicted in 1986 as part of the guns-for-hostages deal that provoked a Congressional investigation. The conviction was overturned in 1991 on grounds that the men had been granted immunity from prosecution as a result of their testimony before Congress .