Today, in its second upward revision, the number of affected people now stands at over 700,000.
As WIRED originally reported last spring, the hack gave attackers access to entire tax returns, which means people's social security numbers, address, and incomes were all compromised. The hackers used personal information already in hand to get unauthorized access through an IRS application called "Get Transcript."
In other words, much of the information had already been acquired, including SSNs and dates of birth. "Get Transcript" has been offline since the first indications of a breach last May.
The initial IRS report indicated that 114,000 accounts had been compromised. It revised that number last August, raising it to 334,000. On Friday, the IRS added another 390,000 accounts to the pile, for a total of well over 700,000 people. There have also been a total of 500,000 targeted, but failed, attempts at access.