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.