BAGHDAD, Iraq -- You don't want to draw attention, so you keep a battered car even if you can afford a fancier model. You don't wash it; better to let dust smear the windows. Night falls, curfew clamps down, and all those dirty old cars wend their way back to the homes of the capital. The eyes of neighbors slide after them.

Where are the drivers coming from? Some work for the government. Some fight with insurgents or death squads. Some are employed by Americans. No one asks, and no one tells; nobody knows who's who.

Bloodshed has turned Iraq into a country defined by disguise and bluff. Violence in the streets has begun to defy logic, and this is part of the fallout: A lively city where people used to butt gleefully into one another's business has degenerated into a labyrinth of disguises, a place where neighbors brush silently past one another like dancers in a macabre costume ball.

"Everything is hidden among Iraqis; people are very suspicious of one another," said 66-year-old Hayawi Mahdi Abaasi, a successful lawyer who says he won't repair his tumble-down house or replace his 1982 Toyota for fear the wrong people would notice.

"Why should I call the attention of terrorists to me? I try to be very common like everyone else," he said.

Rich people hide their jewelry and dig frayed clothes from the back of their closets to evade ransom-seeking kidnappers. Muslims claim to be Sunni or Shiite, depending on circumstance. Christians pose as Muslims. Lying about employment is de rigueur. Street police wrap their faces in masks so nobody will recognize them.

Everybody, it seems, is pretending to be somebody else, adopting a fake identity in the terrified hope of staying safe. Baghdad residents reason that no matter who you are, you're probably on somebody's hit list.

"It's not a matter of lying or not lying," said Ali Abdullah. "It's a matter of life or death."

Mr. Abdullah is a 31-year-old Sunni with dark skin, a strapping build and a bushy strip of mustache. Like most people in Baghdad, he is a man of secrets.

He was trained as an engineer in Saddam Hussein's Iraq but now works for an American nonprofit organization. His life has been threatened and his wife begs him to quit, but he says he can't -- the money is too good, and they have a 3-year-old son to think about.

Abdullah takes a taxi to work so his car won't be recognized. He uses different streets each time and changes his telephone number every few months.

He splurged on a $100 Swatch watch in neighboring Jordan, but now he's afraid to wear it in public. When people ask about his job, he lies and says he owns a computer shop.

Rule No. 1, he says: Never, under any circumstance, intimate to the neighbors on his predominantly Sunni street that he's sold out to the foreigners.

"This is a killer, if my neighbors find out where I work," he said. "This is the first thing that must be maintained, that my neighbors can't know what I do."

For Mr. Abdullah and his family, that has meant isolation. He shrinks from possible conversations, taking care not to linger in his doorway, make eye contact or trade small talk. When he caught sight of an old college friend across a crowded restaurant recently, he turned on his heels and rushed away to avoid conversation.

When they talk about the loss of intimacy, many Iraqis are mournful. Like members of most Middle Eastern societies, Iraqis have traditionally prized warmth and valued social interchange over what Westerners might regard as personal privacy. In the old Iraq, it was better to err on the side of nosiness than to appear cold or distant. It was perfectly normal to grill strangers on their marital status and the price of their possessions.

Little by little, that warmth has been bled away by war. Tension pulls on the city now. The atmosphere is thick with intrigue; it feels film noir, cloak-and-dagger. Except it is real -- and deadly.

"Behavior has changed from rational behavior into instinctive, animalistic behavior," said Ehsan Mohammed Hassan, one of Iraq's leading sociologists and a professor at Baghdad University. "The individual is not safe from the others. He has to hide. He doesn't want people to see him because he thinks the people are evil."

Amid the fear and loathing, a long-standing tribal tradition has disappeared. Etiquette used to require men to ask one another about their jobs; it was a way of showing concern for a friend's livelihood and to demonstrate willingness to help a man if he had fallen on hard times.

These days, though, to ask about jobs is impolite -- perhaps even dangerous. Instead, men find themselves throwing out other questions: How are you? What are you doing here?

"A lot of people are killed for no reason. So what do you think they'll do if you work for the Americans?" Mr. Abdullah asked. "That's it. You're a traitor."

Working for the Iraqi government is no better -- everybody from university professors to national athletes to traffic police has been slaughtered by insurgents determined to bludgeon civic and social life to a standstill.

Iraq may be the only country in the world where militia members and anti-government insurgents walk the streets with bare faces while government workers, soldiers and cops cower behind masks.

"I wear a mask because I don't want people to know I'm working for the police," a 34-year-old officer named Ahmed Ali said on a recent afternoon. It was lunch hour, and he and some of his colleagues had driven across Baghdad through the 110-degree heat to gobble down lamb kebabs in a neighborhood where they knew fewer people.

The men are stationed in the volatile Dora area, south of downtown and one of Baghdad's bloodiest sectarian battlefields. Clad in matching blue button-downs and navy trousers, their pistols holstered on their waists, they admitted they didn't dare bring their badges or uniforms home, not even to launder them.

They described slipping from the house in civilian clothes, creeping into the station and changing hurriedly into their uniforms.

Amid the fear, some profit. The document forger, for one.

Assad Kheldoun, a 29-year-old who operates out of the religiously mixed neighborhood of Shaab, grinds out fake identity cards for about $30 apiece. "Exactly like the original," he boasts. But with one difference: A false name.

He's not selling to hustlers or mischief makers. Most of his clients are bus drivers, highway workers or car repairmen -- people forced to make their livings in Iraq's mean streets.

Last names are sectarian giveaways in Iraq, often deriving from tribes commonly known to be either Sunni or Shiite. Jaabour or Dulaimi, for instance, mean "Sunni" to Iraqis; so does the first name Omar.

"People are getting killed because of their names," Kheldoun said. "In the past few months, everybody is asking for a false identity card. It's a phenomenon now. The people are scared."