The Federal Financial Institutions Examination Council (FFIEC) warned banks about rising cyber-attacks on their websites and their cash machines, urging them to put the proper measures in place to guard against fraud.

The group, which comprises top officials from the Federal Reserve and other bank regulators, said it had seen a rise of so-called denial-of-service attacks on banks' public websites in the latter half of 2012, Reuters reported. These sometimes served as a cover for criminals to commit fraud using stolen customer credentials, it said.

The group also warned the banks that it had seen an increase in cyber-attacks launched in connection with a type of large value cash-out fraud with cash machines, known as "Unlimited Operations."