Once they've handed over their information to scammers, however, the mules often become victims of identity theft themselves, authorities warn.

With a worsening economic situation, scammers may be looking for new ways to take advantage of the growing ranks of the unemployed. McAfee has been tracking these scams for years, and has long seen the scammers reach victims with spam or with ads on job sites. Recently, however, there's been an uptick in money muleing pitches, which are sent out via spam or phoney job postings, said Dave Marcus, director of security research and communications with McAfee’s Avert Labs.

"I think a lot of people are unwittingly coming across them though job searches through Google," he said. "We've seen a huge growth in this."

The prevalence of these fake job ads is up 345 percent over the past three years, according to the most recent data from the U.K.'s Association for Payment Clearing Services, which tracks this activity.

The Web sites recruiting the mules have also become slicker and more believable, Marcus said. "I think they've upped their professionalism," he said. "It's kind of analogous to the way spammers have upped their game professionally."