US agency warns of ‘grave’ threat from long-undetected hack

The hack compromised federal agencies and ‘critical infrastructure’ in a sophisticated attack (Jenny Kane/AP)

US federal authorities have expressed increased alarm about a long-undetected intrusion into computer systems around the globe that officials suspect was carried out by Russian hackers.

The nation’s cybersecurity agency warned of a “grave” risk to government and private networks from the attack which appears to have begun last March.