(Reuters) - U.S. IRS Commissioner John Koskinen said on Tuesday there were about 200,000 attempts to illegally access tax information from February to May this year.
He said of those, about 100,000 were successful. The hackers used the "get transcript" application, which calls up information from previous returns, he said.
"We're confident these are not amateurs, these are actually organized crime syndicates that not only we but everyone in the financial industry are dealing with," Koskinen told a news conference.
Koskinen said the tax agency was originally alerted to the problem by unusual activity in mid-May, which marks the end of the annual tax-filing season.
The attackers already had personal information about the victims and they used that information to try to access the “get transcript” app, he said.
(Corrects March to May in paragraph 1; April to May in paragraph 2)
(Reporting by Brendan Pierson in New York; Editing by Sandra Maler, Richard Cowan and Mohammad Zargham)