WASHINGTON — The Securities and Exchange Commission leveled its most direct shot against billionaire hedge-fund manager Steven A. Cohen on Friday by filing civil charges that accuse him of failing to prevent insider trading.

The SEC alleged that Cohen, who founded and runs SAC Capital Advisors, failed to prevent two of his portfolio managers from illegally reaping profits and avoiding losses of more than $275 million. Both managers provided information to Cohen in 2008 that suggested they had access to inside information, the SEC said. But rather than raise any red flags, Cohen praised one of the managers and rewarded the other with a $9 million bonus, the SEC said.

Cohen, 57, faces possible fines and could be barred from managing investor funds.

Cohen's firm, which once managed more than $15 billion in assets, is at the center of one of the biggest insider-trading fraud cases in history. Four employees have already been criminally charged with insider trading – two of whom have pleaded guilty. And an SAC affiliate has agreed to pay $615 million to settle SEC charges of insider trading.

But legal experts said the SEC's action against Cohen on Friday suggests that the government may not have enough evidence to charge him with insider trading. And rather than seek higher penalties in a federal lawsuit, the SEC chose to bring the case against Cohen before an administrative law judge at the regulatory agency, where the legal burden of proof is lower.

"They've opted for the home court advantage," said John Coffee, a securities law professor at Columbia University.

Coffee said it is significant that the SEC did not charge Cohen with insider trading. That suggests none of his subordinates "flipped" and told investigators that they provided Cohen with information, he said.

A spokesman for SAC Capital said the allegations have "no merit" and that "Steve Cohen acted appropriately at all times." Spokesman Jonathan Gasthalter said Cohen would "vigorously" fight the charges.

The SEC said that Cohen received "highly suspicious information that should have caused any reasonable hedge fund manager in Cohen's position to take prompt action to determine whether employees under his supervision were engaged in unlawful conduct and to prevent violations of the federal securities laws."

The managers that the SEC said Cohen failed to supervise face criminal trials in November. Former SAC portfolio managers Mathew Martoma and Michael Steinberg have each pleaded not guilty to insider-trading charges.

Two other former portfolio managers at the firm, Donald Longueuil and Noah Freeman, pleaded guilty in 2011 to criminal insider-trading charges.

Jon Horvath, a former research analyst who worked for an affiliate of SAC and reported to Steinberg, pleaded guilty to securities fraud last year.

Martoma is accused of earning $9 million in bonuses after persuading a medical professor to leak secret data from an Alzheimer's disease trial between 2006 and 2008.

The SEC has alleged that Sidney Gillman, a doctor who moonlighted as a medical consultant, tipped drug safety data and negative drug trial results to Martoma two weeks before developers Elan Corp. and Wyeth made those results public in 2008. Martoma and CR Intrinsic then caused several hedge funds to sell more than $960 million in Elan and Wyeth securities in a little more than a week.

Steinberg is accused of earning more than $1.4 million illegally in connection with trades involving Dell and Nvidia in 2008 and 2009. The SEC said Steinberg had information about both companies ahead of their quarterly earnings announcements.

Cohen, who lives in Greenwich, Conn., is one of the highest profile figures in American finance and one of the world's richest men. He is among the handful of upper-tier hedge fund managers who pull in about $1 billion a year in compensation.

The SEC action against Cohen culminated a week in which the agency took significant enforcement moves involving prominent Wall Street figures. The actions could signal a new direction and strategy under SEC Chairman Mary Jo White, who assumed office in April.

Since the 2008 financial crisis, public and investor advocates have criticized the SEC for failing to hold high-level individuals on Wall Street accountable for misconduct. White pledged at her Senate confirmation hearing to pursue "all wrongdoers – individual and institutional, of whatever position or size."

The SEC on Wednesday imposed a $13.9 million fine on Rajat Gupta, the former Goldman Sachs board member convicted of insider trading, to settle the agency's related civil charges.

At a closed meeting during the week, the SEC commissioners rejected a proposed $18 million settlement that would have banned billionaire hedge fund manager Philip Falcone from the securities industry for two years. The deal, which was agreed to by the SEC's enforcement staff, was voted down because it wasn't tough enough.

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AP Business Writer Christopher S. Rugaber contributed to this report.

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  • Bernie Madoff

    In what is now considered to be one of the biggest and most famous Ponzi schemes in history, Madoff laundered about $65 billion, <a href="http://www.forbes.com/2009/03/13/bernie-madoff-fraud-personal-finance-financial-advisor-network-ponzi-scheme.html">Forbes reports</a>. Madoff defrauded thousands of investors, all of whom can be found on a <a href="http://www.huffingtonpost.com/2009/02/04/madoff-victims-list-relea_n_164097.html">163-page list</a>.

  • Rajat Gupta

    Ex-Goldman Rajat <a href="http://www.huffingtonpost.com/2012/10/24/rajat-gupta-sentenced-insider-trading_n_2010861.html?utm_hp_ref=business" target="_hplink">Gupta was sentenced to two years</a> in prison for participating in one of the largest insider trading schemes in history.

  • Jerome Kerviel

    Kerviel was found guilty of one of the world's most colosal trading frauds in 2010. He cost France's Société Générale bank 4.9 billion Euros. He was sentenced to 3 years in jail and was also sentenced to paying a $7 billion fine, <a href="http://www.guardian.co.uk/business/2012/oct/24/french-rogue-trader-loses-appeal?newsfeed=true">The Guardian reports</a>.

  • Steven Goldberg, Peter Grimm and Dominick Carollo

    Goldberg, Grimm and Carollo were found guilty of conning the I.R.S. and cities in a "bid-rigging scheme" during their time at General Electric, <a href="http://www.businessweek.com/news/2012-05-11/ex-ge-bankers-convicted-of-municipal-bond-bid-rig-scheme">Businessweek reports</a>. Goldberg was sentenced to four years in prison. Grimm and Carollo were each sentenced to three years.

  • Raj Rajaratnam

    Raj Rajaratnam, the former head of Galleon Management, was sentenced to 11 years in jail in October 2011, the longest prison term for insider trading to date,<a href="http://www.washingtonpost.com/business/economy/hedge-fund-billionaire-gets-11-year-sentence-in-fraud-case/2011/10/13/gIQAa0PZhL_story.html"> The Washington Post reports</a>.

  • Nick Leeson

    During Nick Lesson's time at Bristain's Barings Bank, he lost 862 million pounds and even managed to level the 233-year-old bank itself, according to <a href="http://www.telegraph.co.uk/finance/personalfinance/fameandfortune/9483379/Barings-rogue-trader-Nick-Leeson-Money-is-not-my-motivation.html">The Telegraph</a>. He served four years in a Singapore jail before he was released early with life-threatening cancer.

  • Allen Stanford

    Currently serving 110 years in prison, Allen Stanford was, at one time, one of the richest men in America, <a href="http://www.cnbc.com/id/49276842/Allen_Stanford_Descent_from_Billionaire_to_Inmate_35017_183">according to CNBC</a>. He conned about 20,000 investors out of their money in a Ponzi scheme.

  • Garth Peterson

    Garth Peterson, the former head of Morgan Stanley's Chinese real-estate investments unit, was sentenced to 9 months in jail last August for bribery, <a href="http://online.wsj.com/article/SB10000872396390444508504577593950506343444.html">according to The Wall Street Journal</a>.

  • Bradley Birkenfeld

    Bradley Birkenfeld spent more than 2 years in jail for assisting in income tax evasion while working at UBS. He then volunteered inside information on Swiss banking to the I.R.S., and was rewarded with $104 million for being a whistle-blower, <a href="http://www.nytimes.com/2012/09/12/business/whistle-blower-awarded-104-million-by-irs.html?_r=0">according to The New York Times</a>.

  • Don Of Thieves

    Dennis Levine, Martin Siegel, Ivan Boesky and Michael Milken defrauded Wall Street investors in the 1980's. In a scandalous series of events, Levine stole confidential documents from Lazard Freres investment bank, and the crew made use of inside information, according to <a href="http://www.thedailybeast.com/newsweek/1991/10/13/wall-street-a-greed-apart.html">The Daily Beast</a>.