Thieves used an online service provided by the IRS to gain access to information from more than 100,000 taxpayers, the agency said Tuesday.
The information included tax returns and other tax information on file with the IRS.
The IRS said the thieves accessed a system called “Get Transcript.” In order to access the information, the thieves cleared a security screen that required knowledge about the taxpayer, including Social Security number, date of birth, tax filing status and street address.
“We’re confident that these are not amateurs,” said IRS Commissioner John Koskinen.
Koskinen said the agency was alerted to the thieves when technicians noticed an increase in the number of taxpayers seeking transcripts.
The IRS said they targeted the system from February to mid-May. The service has been temporarily shut down.
Taxpayers sometimes need copies of old tax returns to apply for mortgages or college aid. While the system is shut down, taxpayers can still apply for transcripts by mail.
The IRS said its main computer system, which handles tax filing submissions, remains secure.
The IRS has launched a criminal investigation. The agency’s inspector general is also investigating.