The feds warned that "a group of malicious cyber actors," whom security experts believe to be the government-sponsored hacking group known as APT6, "have compromised and stolen sensitive information from various government and commercial networks" since at least 2011, according to an FBI alert obtained by Motherboard.The alert, which is also available online, shows that foreign government hackers are still successfully hacking and stealing data from US government's servers, their activities going unnoticed for years. This comes months after the US government revealed that a group of hackers, widely believed to be working for the Chinese government, had for more than a year infiltrated the computer systems of the Office of Personnel Management, or OPM. In the process, they stole highly sensitive data about several millions of government workers and even spies.