As the numbers of mobile banking users increases, so too do the efforts of mobile hackers. A study last December found that 73 percent of the top free apps for Android users were breached in 2013.

And now a new investigation by GoBankingRates.com has found that nearly two in five mobile banking app users — 37 percent — are worried about identity theft.

GoBankingRates found that though 44 percent of respondents have no major concerns about mobile banking, more than half do have significant fears — including technical errors resulting in missing funds (9 percent), misuse of information by companies (7 percent), and lack of paper documentation (3 percent).

"What most Americans don't realize is their personal information is out there — whether or not they choose to bank online or over their phone," said GoBankingRates editor Christina Lavingia. "And security breaches are inevitable — they might happen when major retailers are hacked, as we've seen multiple times throughout the last year, or simply because someone is looking over your shoulder at the ATM. Mobile banking offers numerous benefits that shouldn't be ignored; the trick is to be safe about banking in the digital age, not to avoid it completely."

The GoBankingRate study also found that:

• older respondents were more likely to be concerned with identity theft than younger ones;
• the lowest income brackets polled ($0 to $49,999) were least likely to have any concerns about mobile banking; and
• Women are 65 percent more likely than men to be most afraid of technical errors resulting in missing funds.

View the complete study results online.