WASHINGTON >> The software was called Tax Bandits. The scheme, which was run out of a prison in California, federal officials said, attempted to fraudulently claim more than half a billion dollars in tax refunds.

The method was a familiar one: erroneous claims of the Employee Retention Tax Credit.

The IRS said on Friday that it was intensifying its efforts to root out such cases of fraud and attempted fraud as it tried to safeguard taxpayer money, but it acknowledged that without an intervention by Congress, the agency would continue to be flooded with potentially improper claims.

One of the most brazen cases connected to the program emerged in February, when federal agents announced charges against a man they called the ringleader of a fraud operation, Kristopher Thomas, a former gang member who was already serving prison time for murder.