Late last year, more documents suggested that the NSA was able to decrypt massive amounts of traffic going through Virtual Private Networks (VPNs), a common tool used by businesses as well as individuals use to connect securely to the internet.

The documents did not reveal exactly how the spy agency was able to break the encryption in these cases. Now, thanks to new research, we might finally know. And it turns out that it was probably thanks to outdated and weak encryption technology.

A group of computer scientists and cryptographers has discovered a series of vulnerabilities in the Diffie-Hellman key exchange protocol, a widespread protocol used on the internet to secure connections, that can be exploited to intercept and read supposedly secure connections.

In their paper published on Wednesday, the researchers also show practical attacks, dubbed "Logjam," against this vulnerabilities.