China’s “Great Firewall” blocks Web access to, among other things, Facebook and Twitter. People in China can get around the firewall, and very Web-savvy Chinese often do, by using something called VPNs, or Virtual Private Networks. But Chinese hackers already have access to what is presumably an extremely sophisticated VPN: the very servers they use for their foreign hacking.

This where the hackers may have gotten themselves into trouble. To be totally safe, a Chinese hacker would log out of the servers used for cyber-espionage (and allegedly sponsored by the Chinese military) before logging into a separate, more low-key VPN that he or she could use to access U.S.-based social media sites such as Facebook and Twitter.
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