What social media platform did Russian hackers use to break into U.S. computer networks?

Hacker groups believed by security firm FireEye to be sponsored by the Russian government have been using Twitter to gain access to U.S. networks. The hacker group, dubbed APT29, uses a tool called “HammerToss” that generates new Twitter handles to blend into the crowd and share images that, if opened, might subject viewers’ devices to malicious code.