Internal Revenue Service
At the height of tax season, the Internal Revenue Service announced that it had been hit by a massive data breach, exposing the information of more than 700,000 individuals. Hackers accessed the information, including Social Security numbers and other personal information, through the IRS' "Get Transcript" program, which was created to allow taxpayers to check their history online. The hackers potentially accessed the accounts using data from breaches of IRS-approved tax preparers or other online accounts, the IRS said at the time. The IRS first reported the breach in May 2015, saying it affected 114,000 accounts. That number was expanded in February of this year to include as many as 724,000 accounts affected.