The veteran FBI agent was trained all too well. The very professionalism the Chicago native brought to the task helped him operate without detection for more than a decade as a spy for Moscow, the FBI says.
A father of six living in a middle-class Virginia suburb, Hanssen knew how to hide his identity even from his handlers and how to watch the FBI to see if it was watching him, authorities said after charging him with espionage.
As CBS News Correspondent Bob Orr reports, his many of his colleagues never suspected and have a hard time believing that their co-worker may be a spy.
They say they knew the FBI agent to be a "quiet guy" with a "good reputation."
"He was a real pro. He knew counter-intelligence. He is a very bright man. He was an expert in technology before technology became a big issue. He was one of the brightest people I knew in the FBI," said David Major, who used to supervise FBI counterintelligence agents.
Former agent Rusty Capps said it's hard to accept allegations that Hanssen betrayed the public trust.
"Bob Hanssen was one of those people that you'd least believe it of, because he was a very, very bright guy," Capps said.
And neighbors here in this Northern Virginia suburb describe Hanssen as a quiet man who seemed to be devoted to his family. Nothing about his lifestyle, they say, stood out: No obvious money problems, no lavish spending.
According to the FBI, Hanssen knew of the risks he was allegedly taking.
"I know far better than most what mine fields are laid and the risks," Hanssen wrote to a KGB handler, according to correspondence quoted by FBI Director Louis Freeh.
"In short, the trusted insider betrayed his trust without detection," Freeh said.
For Hanssen, an FBI career that began with his taking the agency's oath ended in a Virginia park Sunday night, where colleagues read him his Miranda rights.
Nothing special set him apart in his Vienna, Va., neighborhood, say the neighbors, although one complained that he let his dog roam and create a nuisance.
Hanssen, 56, made a home for himself, his wife and their children in a $300,000 split-level, brick-and-cedar house with a one-car garage, a Ford Taurus and that other symbol of suburban living a minivan. A basketball hoop is in the driveway.
Hanssen's wife, Bernadette, teaches religion part-time at a local Catholic high school, and the family came regularly to block parties, such as the one every Memorial Day.
"Not overly gregarious," Nancy Cullen said of him. She lives several doors down from the Hanssens in a cul-de-sac she describes as "our town hall."
When neighbor called neighbor to share the news of his arrest, the reaction was, "No way," Cullen said.
"I've been in his house. I've never seen any Soviet flags or anything like that, if that's what you're asking," said Matt Bennett, who lives across the street.
The government says Hanssen had a long relationship with the Soviet Union and the Russians, dating back to 1985, while assigned to the intelligence division of the FBI field office in New York City.
Operating under the code name "Ramon," Hanssen kept his real identity a secret even from his Russian handlers, who did not find out his name or who employed him until his arrest was disclosed, Freeh said.
Hanssen also checked his agency's own security systems to see whether authorities had any suspicions about him which they apparently did not until late last year.
"He was, after all, a trained counterintelligence specialist," Freeh said.
From February 1995 until January, Hanssen was the FBI's senior representative to the State Department's Office of Foreign Missions, where he oversaw an interagency counterintelligence group.
He was returned to FBI headquarters last month in a newly created position designed so that the bureau could monitor his daily activities without alerting him to its investigation.
Hanssen apparently contemplated several careers before settling on one in law enforcement.
He earned a bachelor's degree in chemistry from Knox College in Galesburg, Ill., in 1966, according to the government's information.
He then studied dentistry at Northwestern until 1968 before receiving a master's in accounting from the university in 1971. He became a certified public accountant in 1973.
He worked as a junior accountant at a Chicago firm from 1971 to 1972, when he joined the city police department as an investigator in the financial section of its inspection division.
Hanssen joined the FBI in January 1976, and served initially iIndiana before assignments that took him back and forth between offices in New York and the Washington headquarters.