Representative Mike McCaul, a Texas Republican, asked when cyberattacks cross the line into warfare. "At what point do we respond?" he said.
Berman said he couldn't answer that question. Instead, U.S. defense and intelligence officials need to make that decision, he said.
Cyberattackers are changing their tactics as large U.S. companies harden their defenses, said Richard Bejtlich, CSO at security vendor Mandiant, which recently pinned responsibility for several espionage campaigns on a Chinese government cyberunit. Attackers are often targeting smaller companies that partner with large organizations, and then working their way in to the larger target, he said.
The attacks are often successful because "there's an imbalance between offense and defense," Bejtlich added. "A single attacker or group of attackers can keep hundreds or thousands of defenders busy."
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