An IRS computer breach leaving hundreds of thousands vulnerable to thieves is a lot worse than people originally believed. More than 220,000 potential victims had information stolen from them. Hackers stole these victims' identities to claim fraudulent tax refunds, according to the Associated Press.

In May, it was believed that criminals hacked the IRS website ,stealing tax forms from 104,000 people, according to CNN Money.

This new information more than doubles the number of potential victims previously estimated, bringing the number to 334,000, according to the AP.

The hackers' way in was through the "Get Transcript" tab on the online application, according to Reuters. The tab allows taxpayers to look up previous returns. After the attacks in February, the system was shut down.

What is so astounding about this hack was that it wasn't a hack at all. Nobody broke into any servers or databases. They simply took advantage of a tool the IRS had created, according to CNN Money.

The IRS is now notifying the potential victims, sending letters warning of potential identity theft, and offering free credit protection while giving extra PIN numbers to protect themselves in the future, according to CNN Money.

A potential source has yet to be identified, though it is believed that the thieves are part of an elaborate criminal operation in Russia, according to the AP.