Financial and retail industry call centers have seen a 30 percent spike in over-the-phone scams since 2013. Researchers at Pindrop Security found, on average, one in every 2,200 calls was fraudulent, according to its annual Phone Fraud Report that was released Wednesday.

Attackers are targeting consumers directly as well. The report found more than 86.2 million calls monthly in the U.S. are scams. IRS and technical ploys are among the most popular. "When attackers are able to pass knowledge-based authentication (e.g. personal security questions), financial institutions risk major monetary losses, as well as regulatory compliance and privacy issues," the report said.

The study noted that attackers use free or cheap voice over IP (VoIP) for 53 percent of their calls - in comparison, the general public uses VoIP for only 7.8 percent of calls.