Massive hack of US government launches search for answers as Russia named top suspect By: CNN By Zachary Cohen, Alex Marquardt and Brian Fung, CNN (CNN) -- Days after several US agencies confirmed their networks were compromised in a massive data breach, federal officials are still struggling to understand the scope of the damage -- highlighting the sophistication and breadth of an ongoing hacking campaign that has been tied to Russia. House and Senate Intelligence Committee aides received a phone briefing on the hack from administration officials on Wednesday, but the full extent of the breach remains unclear, according to sources familiar with the briefing. The Biden transition team was also briefed on the attack this week, an official from the Department of Homeland Security's cyber arm told CNN. The official declined to provide additional details about what was discussed.