More than a dozen years after the last graffiti-covered subway train was takenout of service, a little-known police squad combs the tunnels and hideoutsof the subway system each night for signs of trouble.

"It's not as glamorous as homicide," said Lt. Steven Mona, commanding officer of the Vandals Squad.

It is filthy but essential work that became more important for this city after the September terrorist attacks.

"We're out there every night, inspecting tunnels and rooms, alcoves and storageareas and equipment boxes," said Mona, 42, who has made a career in the squad."We make sure they're all locked and secure. This is something we've beendoing since way before 9/11."

They're among a select group of policeofficers allowed on the subway tracks when the third rail is alive with power.They receive the same training as the grunts of the transit workforce, theundervalued men and women known as subway track workers.

"The subway is the lifeblood of the city," Mona said. "If you shut the subways down, the city comes to a standstill."

Still, fighting graffiti is their bread and butter. Their beat is a cityand subway system widely acknowledged as the Mecca of graffiti art, the placewhere it all started with a handful of rebellious South Bronx vandals inthe late '60s.

In graffiti's heyday, in fact, underground artistswould routinely gather at the 149th Street-Grand Concourse subway stationin the South Bronx to study and admire the pieces painted on the IRT's No.2 and 5 trains.

Today, graffiti artists from Germany, Italy, Japan,Norway and Sweden make pilgrimages to New York. They don't come to see theskyscrapers or visit the Statue of Liberty, but to experience up close thebirthplace of their waning movement. Many return home disappointed with thestate of graffiti in this city, especially in the subway.

Since thelast spray-painted subway went out of service in 1989, New York City Transithas done a marvelous job of keeping graffiti off the trains. Each year thetransit agency spends millions of dollars cleaning the stuff almost as soonas it appears.

But the subterranean culture never went away, andgraffiti has evolved from the spray-painted murals on the side of subwaycars to the annoying "scratchiti" writing on subway car windows. Scratchitiis the etching of nicknames into subway car windows and walls with keys,blades or sharp rocks formed from lava.

"The graffiti world looksdown on scratchiti," said Det. Jim Bogliole of the Vandals Squad. "For some,scratchiti is the lowest."

The graffiti subculture has developedinto an international circuit, linked partly by hundreds of Internet sitesand cheap airfares.

In recent years, authorities in Germany and otherEuropean countries have replicated the Vandals Squad in an attempt to dealwith the burgeoning graffiti problem there.

Still, no country hasanything on the size or scale of the NYPD, which began its anti-graffiticampaign in earnest during the early '80s.

"The perception of crimein the subway was that it was absolutely the most dangerous place in thecity to be," Mona said of the turbulent '70s and '80s. "The perception wasthat, at best, no one was in control of the subway system and, at worse,the criminals were in charge."

Now, the Vandals Squad has eight sergeantsand 60 officers who patrol the city's train yards and tunnels, monitor thehundreds of graffiti sites on the Internet and conduct surveillance operationson graffiti writers from here and abroad.

"We're out in the yards and tunnels every night," Mona said.