United States security agencies warned Tuesday that Chinese government-backed hackers have breached "major" telecommunications firms by exploiting known software vulnerabilities in routers and other popular network networking hardware. An advisory was released by the FBI, the National Security Agency, and US Cybersecurity and Infrastructure Security Agency. It stated that the "devices are often overlooked by cyber defenders, who struggle to maintain and keep pace with routine software patching of Internet-facing services and endpoint devices." Although the hacker victims were not identified, the warning focused on measures to help enterprises using Cisco, Fortinet, and other suppliers secure their networks, according to…