The two California men have been charged in an indictment by the US Justice Department in Boston with one count of conspiracy to commit computer intrusion and wire fraud, and one count of wire fraud.

According to the indictment, Holdt owned Subway franchises in Southern California from 2005 to 2008, and later operated a California company called POS Doctor, which sold and installed point-of-sale computer systems to Subway restaurant franchises around the country.

The DoJ alleges that members of the conspiracy hacked into at least 13 Subway POS systems that Holdt sold through POS Doctor and fraudulently added at least $40,000 in value to Subway gift cards.

Holdt and Wilkinson allegedly used the fraudulent gift cards to make purchases at Subway, and Wilkinson also allegedly sold fraudulent gift cards to others using eBay and Craigslist.

Earlier this year a Romanian man was sentenced to 21 months in prison for his part in an unrelated scam that saw the point-of-sale systems of hundreds of US Subway sandwich shops hacked, thousands of cards compromised and millions of dollars stolen.