HANOI, Vietnam - Most Vietnamese cower when a police officer squeezes them for a bribe. Le Hien Duc, a gray-haired 75-year-old grandmother, fights back.

Though just 4-foot-9 and 88 pounds, she will take on anyone, from lowly bureaucrats to high-level officials. She e-mails, phones, tracks them down at their offices, confronts them at their homes.

"Corruption is definitely an evil, and it is ruining my beloved country," said Duc, a former elementary schoolteacher who works from dawn until dusk battling graft.

Corruption is perhaps the most vulnerable spot in the country's single-party communist state - from the traffic officers who pull drivers over for $3 bribes to the Transportation Ministry officials accused last year of gambling $13 million in public money on British soccer matches.

Corruption persists here in part because officials consider it perfectly acceptable to charge kickbacks for virtually any kind of service, large or small.

As a result, the country routinely fares poorly in corruption rankings. But in Vietnam, where people respect authority, few dare challenge the system. Many turn to Duc.

"Most of us tremble when we have to deal with police," said Doan Van Hung, a deliveryman who recently sought Duc's help. "She is incredibly brave."

Hung's ordeal was typical - a policeman stopped him for speeding and threatened to seize his motorbike unless he paid a $3 bribe - more than a day's average wage.

Corruption among "road bullies," as the Vietnamese traffic police are known, is rampant. But most drivers simply pay up and leave.

Duc tracked down the officer who harassed Hung and filed a complaint with the Hanoi chief of police. The officer was promptly demoted.

Duc, a grandmother of eight, intervened in another recent case involving school officials who had apparently been pocketing school lunch money for years by making cafeteria staff cut back on the children's portions.

Local government investigators confirmed the scam. But when the evidence was brought before Hanoi education officials, they did nothing.

Frustrated parents had read about Duc in the newspapers and turned to her. She took the case straight to the top.

She said she called the office of the education minister, Nguyen Thien Nhan, about 30 times.

When her messages went unanswered, Duc managed to discover the minister's cell-phone number and called him. He promised to have the department's internal investigator look into the case.

Duc has spent a lot of time investigating where government and party leaders live and work. If they won't meet her at their offices, she shows up at their homes.

Duc runs her crusade from her narrow, three-story home in Hanoi. She spends about two-thirds of her $80 monthly pension on the Internet, phone calls, photocopying and motorbike taxis.

Her work has made enemies.

Last month, people went to her house and told her to butt out of the school-lunch scam.

"Drop the case or start saving money for your coffin!" they shouted.

Her children wish she would give up her work.

"She is too old and weak to protect herself," said Pham Minh Hai, Duc's daughter. "She should stay home and play with the kids."

Duc has no intention of quitting. "There is no excuse for anyone to abuse their authority. I cannot stand seeing corrupt officials bully people."