Outside Gate 15 of Fiat's giant Miraflori auto plant, a group of Communist militants waits for the changing of the shift.

As workers in overalls begin streaming through the factory gate, one of the Communists begins haranguing them through a megaphone, mimeographed flyers.

Their message: "Workers, the atrocities of terrorism represent a threat to democracy and a blow against the working class."

Efforts by Italy's Communist Party and the giant labor federation to convince rank-and-file workers that they must aid in the nationwide fight against terrorism have been going on for some time.

But last week's kipnaping of former premier Aldo Moro by the Red Brigades appears to have given the campaign new thrust. For the first time, the effort appears to be bearing fruit.

"Anyone who is a worker is against this type of thing," an employe in the Flat metal presses section remarked.

"Human life, no matter whose, is sacred," said a burly worker as he passed through Gate 15.

This country's major industries have been a prime target of terrorists since the Red Brigades began operating here in 1970, and there has been a special focus on Flat - Italy's largest and most successful private firm.

Since 1972, three Flat executives have been kidnaped, one has been beaten up, 12 have been shot and wounded, and one has been killed. Since March 1976, furthermore, there have been six cases of industrial arson and sabotage. The cars of three of the company's medical consultants have been burned, and the residence of a top Flat employe in Milan was bombed.

More than half the Red Brigades attacks last year in this northern city were directed against Flat and its personnel.

A major issue in Italy in recent months has been the degree to which the labor force - at Flat and elsewhere - may have been "infiltrated" by terrorists or sympathizers willing to provide key logistical information.

Suspicion of worker complicity has been fed by the discovery within Flat, and other major plants, of Red Brigades leaflets. One of the 49 Red Brigades member currently on trial here was originally a Flat worker, and widespread worker apathy often greeted past attacks on business executives.

More Flat executives, however, seem to agree with trade unionist claims that the terrorists within the factory are an isolated few.

At a small Communist Party branch office, a grizzled party worker busy at the mimeograph machine said the major problem was indifference.

"We've got to convince as many workers as possible that violence is unacceptable in principle," said Bruno Aroppoli.

Other Communists admit that the party's concern is also political.

"If terrorism provokes a right-wing backlash, the union movement would be the first to suffer," a high-placed Turin Communist said.

Party and union workers nevertheless, believe that most Flat workers distrust the ploice, and are therefore reluctant to name persons suspected of connivance with terrorists.

Over 150 alleged members of the Red Brigade, are currently behind bars, but many workers appear baffled that police have so far been unable to find the men and women responsible for 1977's bout of Flat shootings and killings.