More Than 300,000 Taxpayers Affected by Hack, IRS Says

Tax return information for about 300,000 U.S. taxpayers was illegally accessed by cyber criminals, says the IRS. The agency reported in May that just 100,000 taxpayers were affected. Jonathan Ernst/Reuters

A massive breach of U.S. taxpayers' information is more extensive than previously thought, The Wall Street Journal reports, affecting more than 300,000 taxpayers.

In May, the Internal Revenue Service (IRS) reported that hackers, later believed to be from Russia, used Social Security numbers and other information acquired elsewhere to penetrate its computer databases. The hackers used this data to access about 100,000 U.S. taxpayers' prior-year tax return information.

On Monday, the IRS said that an internal review showed an additional 390,000 taxpayers were potentially affected, including around 220,000 additional households. The agency also said it identified about 170,000 "suspected attempts that failed to clear the authentication processes."

The IRS said it will immediately begin to notify the taxpayers affected and offer free services, like credit protection, to reduce tax refund fraud.