Earlier this week, the IRS announced that they discovered and stopped an automated cyberattack on the e-filing personal identification number (PIN) system last month. In this attack, cyber thieves used information stolen “outside the IRS” to generate e-file PINs for stolen Social Security numbers (SSNs). The Journal of Accountancy reported that the cyber thieves were unable to steal any additional information, but they did use the 101,000 SSNs they’d stolen elsewhere to access e-file PINs.

The IRS is currently notifying the affected taxpayers and placing tax return identity theft markers on their accounts. They’re also monitoring the Electronic Filing PIN application, on alert for additional breaches.