A Chantilly, Va., man who works as a computer expert in the Defense Department was held in lieu of $250,000 bond after a federal court hearing yesterday in which after prosecutors described him as a key figure in an international child pornography ring.

Prosecutors allege that William Moulton Inglis, 35, a computer expert with the Defense Communications Agency, took part - along with at least five other persons - in a conspiracy to recruit young Baltimore boys to perform in pronographic movies and pose for pornographic photographs that were distributed nationally and in Europe.

At least one of the movies, called "Strip Poker," was filmed at Inglis' house, Marsha Ostrer, an assistant U.S. attorney, told the presiding magnistrate yesterday.

Indictments were returned against the six persons by a federal grand jury Wednesday and unsealed Thursday afternoon. The six are charged with conspiring to operate a child porongraphy business which procured males between the ages of eight and 18 for the filming of explicit sexual acts.

The indictments list almost 4,000 copies of films which allegedly were shipped around this country and to Europe through an international network of supplies. The network was operating between 1975 and last December.

Bail for anther coconspiritor, Larry MacDunn, 53, a self-employed Baltimore bookkeeper, was set today at $25,000. Dunn, according to the 24-count indictment, played only a minor role in the operation.

Bond for a third Baltimore man, Donald Eugene Masken, 37, was set Thursday at $75,000. He was charged with mailing and transporting the films. A fourth man indicted Wednesday was David Elliott Houstle, 38, whom prosecutors described as the leader of the pornography ring. Also indicted were Peter Thommen of Switzerland and Victor Rothlisberger, a German national living in Switzerland.

Prosecutors said they believe Houstle may have fled the country and may now be in Guatemala. His attorney, Andrew J. Graham, said today, "I don't know where he is."

Inglis, an honor graduate of the Massachusetts Institute of Technology who holds two masters degrees has been a GS-14 employe of the DCA for about six years. He now faces a maximum sentence of 110 years in jail if convicted of the charges against him.

"He possessed knowledge that only four or five people in the country have" and he was an expert in security matters, said Ostrer. "If he decided to leave the cuntry, he would be highly employable in any country he decided to go," she added in asking the court to set a $200,000 bond.

Inglis had a "top security" clearance before he was charged in 1976 with child molesting in Northern Virginia. At that time, his security clearance was reduced to a "secret" grade.

While he was not convicted of any offense, a state court placed Inglis on prbation in the Virginia case. As a special condition of his 14-month probationary period. Inglis was not supposed to associate with young children, prosecutors said.

Federal magistrate Federick C. Smalkin who set Inglis' bond at $250,000 which was $50,000 higher than prosecutors had requested said the charges in the indictment were "revoting" beyond description for most civilized persons.

Smalkin said there was a risk that Inglis might flee the country and rejoin Houstle - described in court as a former high school classmate of Inglis. Guatemala, where Houstle is alleged to be, has no extradition treaty with the United States covering this type of charge.

"He (Inglis) was at one time in an extremely sensitive position with the government." Smalkin said, making him "a threat to national security."

Inglis has worked for the federal Defense Communications Agency as a computer specialist since 1971, first at a facility in Reston and most recently at the main headquarters in Arlington, according to John Whealen, the agency's counsel.

"We can further restrict his clearance if we have evidence to act on." Whealen said. he added, "I can't tell you what the future will be. He has been accused, but it doesn't mean he's guilty."