Cisco logo is seen on August 30. Jakub Porzycki/NURPHO/AP/File

US cyber officials issued an “emergency directive” Thursday ordering federal agencies to defend their networks against an “advanced” group of hackers that have breached at least one agency in an apparent espionage campaign.

Government officials have not commented on who is behind the hacks, but private experts say they believe the hackers are state-backed and based in China. The hackers have been exploiting previously unknown flaws in software made by Cisco for several months.

“We are aware of hundreds of these devices [running the affected Cisco software] being in the federal government,” Chris Butera, a senior official at the Cybersecurity and Infrastructure Security Agency, told reporters.

The directive will help offic

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