US tax authorities: Data breach more extensive than previously disclosed

The Internal Revenue Service ( IRS) revealed on Monday penetration by identities thieves of one of its website wreaked havoc more seriously than originally thought, with an additional 220,000 taxpayer accounts potentially compromised, the Wall Street Journal said.

According to the Journal, the IRS's recent review showed that an additional 390,000 taxpayers were potentially affected by data breach, including about 220,000 household accounts "where there were instances of possible or potential access" to prior-year return data, as well as 170,000 additional instances of "suspected attempts that failed to clear the authentication processes."

The IRS first disclosed in May that identities thieves used one of its data base to obtain prior-year tax return information for about 114,000 U.S. households. In addition, another 111,000 unsuccessful attempts were also found by the IRS.

By using stolen Social Security numbers and other data, the identities thieves were believed to access an IRS online application called "Get Transcript", where taxpayers can get prior- year return information.

The IRS said the information stolen from its data base, together with personal information presumably stolen from other sources, could help identities thieves claim fraudulent tax refunds in the future.

The IRS on Monday did not identify a potential source of the breach, but in June, the U.S. TV network CNN cited U.S. officials as saying that the cyber breach originated in Russia.