The IRS identified and halted a cyberattack involving 464,000 unique Social Security numbers. The attack occurred last month.
The automated attack focused on the Electronic Filing PIN application on IRS.gov. Of the 464,000 SSNs, 101,000 were successfully used to access an e-file PIN. No personal taxpayer information was compromised or disclosed by IRS systems, according to the breach notice.
The IRS is sending notices to the affected taxpayers. Additionally, the government organization is working with the Treasury Inspector General for Tax Administration and cybersecurity experts to assess the situation.