The alleged $50 billion fraud by Wall Street financier Bernard Madoff has prompted an outpouring of anti-Semitic comments on mainstream and extremist Web sites, the Anti-Defamation League said on Saturday.

The Jewish-American organization said some of the posts on the highly trafficked sites spread conspiracy theories about Jews stealing money to benefit Israel and suggest that, "Only Jews could perpetrate a fraud on such a scale."

These and other anti-Jewish tropes about Jews and money have appeared on popular blogs devoted to finance, in comment sections of mainstream news outlets and in banter among users of Internet discussion groups, according to the ADL.

"Jews are always a convenient scapegoat in times of crisis, but the Madoff scandal and the fact that so many of the defrauded investors are Jewish has created a perfect storm for the anti-Semites," said Abraham H. Foxman, ADL National Director.

"Nowadays, the first place Jew-haters will go is to the Internet, where they can give voice to their hateful ideas without fear of repercussions."

Meanwhile, Madoff's alleged scam has caused deep ripples in the Jewish philanthropic world, forcing the closure of two prominent U.S.-based charities and threatening the financial lifeline of a slew of other groups.

Hadassah, the Women's Zionist Organization of America, said Thursday that it has lost $90 million it invested with Madoff.