Big U.S. Banks Face Increase in Attempted Cyberattacks

Some large U.S. banks have seen an uptick in attempted cyberattacks in recent weeks, according to people familiar with the matter, at a time when federal officials are stepping up warnings to banks about cyberthreats.

The federal officials have asked the banks—which include Bank of America Corp., Citigroup Inc., JPMorgan Chase & Co. and Wells Fargo & Co.—to monitor traffic from hackers who appear to be searching for weaknesses in the firms’ networks, these people said.