After the OpenSSL Heartbleed bug and the SSL 3.0 POODLE vulnerability another encryption attack has emerged that enables exploiters to read and modify data passing through encrypted connections. According to an Ars Technica article this new attack leaves tens of thousands of HTTPS-protected web and mail servers vulnerable.
Possible attackers might use this new vulnerability, called Logjam, to downgrade encrypted connections between a user and a web or mail server to 512-bit cryptography, which is weaker and can more easily be decrypted.
Since version 14.4.12 (released in October 2014) PRTG Network Monitor is safe. We use unique pre-generated Diffie-Hellman (DH) parameters, which use a 1024-bit key as a default. If you're interested in how you can generate a DH key that is longer than the existing default key in PRTG, please have a look at this Knowledge Base article on "Modifying Key Length for Diffie-Hellman Parameters".
You can test the security of your PRTG server at weakdh.org—if your PRTG installation is up-to-date, you will receive a similar result as the following:
If you are using a PRTG version older than 14.4.12, please update to the newest PRTG stable release: