Sen. John McCain, R-Ariz., on Thursday lashed out at Google and Yahoo at a Senate hearing on malicious advertising that seeks to defraud consumers online, saying the technology giants are ignorant of the scale of the problem.

Appearing before the Senate Homeland Security and Governmental Affairs Committee’s investigations subcommittee, Yahoo Inc. chief information security officer Alex Stamos and Google Inc. senior product manager George Salem disputed the accuracy of an analysis finding that “malvertising” increased 225 percent from 2012 to 2013. The findings, which McCain touted, came from Internet security company RiskIQ Inc.