Merchant acquirers are making big changes to fight a recent surge in card fraud, but those changes could cost credit unions a lot of money.

According to Monica Eaton-Cardone, co-founder and COO of dispute mitigation and risk management firm Chargebacks911, a spike in card-not-present fraud in recent months has prompted acquiring banks to put more and more online retailers on their unapproved lists. The result is a mushrooming number of declined transactions, which could threaten interchange income for credit union card issuers.

"The risk of fraud and the expense of fraud has become such an issue in the industry that it happens to be the one enemy that everybody has in common," she told CU Times. "So even the acquirers now are saying, 'What things are you guys doing on your end to help proactively prevent these types of things?'"