The Justice Department official credited with bringing down hedge fund billionaire Raj Rajaratnam is a wisecracking, self-effacing, Bruce Springsteen-loving prosecutor who is deadly serious about what he views as rampant insider trading on Wall Street.

Preet Bharara, the U.S. attorney in Manhattan, has been hailed by some in the financial media as the “sheriff of Wall Street.” His office has ramped up white-collar enforcement, charging nearly 50 people in an insider trading crackdown that led to Wednesday’s conviction of Rajaratnam, founder of the Galleon hedge fund, on 14 counts of fraud and conspiracy.

Yet some who know Bharara, while crediting him with aggressive enforcement, say he is following the tradition of an office known for policing Wall Street since Ivan Boesky and Michael Milken were sent to prison two decades ago. The Rajaratnam investigation began during the George W. Bush administration, though Bharara oversaw the case after taking office in August 2009.

“I think this ‘Sheriff of Wall Street’ stuff is a bunch of press hype,” said David N. Kelley, a former U.S. attorney in Manhattan. “Preet is doing what all U.S. attorneys have done. . . . He’s a very effective prosecutor and lawyer, and he’s very smart.’’

Bharara’s 21-month-old tenure heading one of the nation’s most important federal prosecutor’s offices has not been without setbacks. Attorneys for the first Guantanamo Bay detainee tried in U.S. federal court under the Obama administration won acquittals on 284 of 285 counts, though Bharara’s prosecutors secured a life prison term for the defendant, Ahmed Khalfan Ghailani.

Even with the historic crackdown on insider trading, some critics have questioned why the administration has brought few major criminal cases stemming from the financial crisis.

And through no fault of his, Bharara lost what he called the “awesome responsibility” of overseeing the prosecution of accused Sept. 11 mastermind Khalid Sheik Mohammed and four alleged co-conspirators. That case was recently transferred to the U.S. military.

But Bharara, 42, is credited with a successful run in which his office rapidly secured a life prison term for the would-be Times Square bomber; unraveled a ring of Russian spies and brought cases against allegedly corrupt New York officials, mafia figures and narcotics traffickers.

And the naturalized U.S. citizen, who was born in India and immigrated to the United States at age 2, is widely respected even among Republicans for his role in helping to lead the investigation into the firing of U.S. attorneys during the Bush administration. As chief counsel to Sen. Charles E. Schumer (D-N.Y.), Bharara interviewed witnesses and negotiated with the Bush Justice Department.

“He conducted himself with extreme professionalism. He was not a partisan witch hunter,” said Bill Burck, a former deputy counsel to Bush who has known Bharara since the two were prosecutors in the Manhattan U.S. attorney’s office.

Bharara, who is married and has three children, prosecuted organized crime, fraud and other cases in that office from 2000 to 2005 before coming to Washington. Schumer later recommended him for the U.S. attorney job.

Hanging in his office in Lower Manhattan is a picture of Bharara’s mother with Springsteen, whose music often wafts through the office when the prosecutor works late.

Those who know Bharara say his low-key style relies on humor and self-deprecation. During his White House interview for the U.S. attorney’s post, friends say, he joked about his Indian heritage by saying: “Hey, you have to be a U.S. citizen for this job?”

In 2009, he told New York University law students that financial fraud “has been with us through the ages . . . Unscrupulous cavemen no doubt fleeced unsuspecting Neanderthals out of clubs and animal skins when the opportunity arose.’’

But he also described insider trading as “rampant” in a speech last year. “It is unfair; it is offensive; it is unlawful,” Bharara said.

Colleagues say Bharara has maintained his office’s traditional independence while keeping good relations with top Justice officials in Washington. He is “both highly regarded and well liked by his fellow U.S. attorneys and DOJ brass alike,” said Neil H. MacBride, the U.S. attorney in Alexandria.

He called Bharara “a prosecutor’s prosecutor.”