To server admins.
I recently received a long notice (in German) and the server was blocked by the company I rent the 'box' from. It is not a managed server so they can't or won't help. I have it back up at the moment but they expect me do something, close ports I think, but I'm at a loss as to which ports I can close and which ones need to be open.

Anyone had anything like this before? An extract of the message:-


Sir or Madam,

Multicast DNS (mDNS) is used for resolving host names to IP addresses within small networks that do not include a local DNS server. It is implemented for example by the Apple 'Bonjour' and Linux/BSD 'Avahi'(nss-mdns) services. mDNS uses port 5353/udp.

In addition to disclosing information about the system/network,mDNS services openly accessible from anywhere on the Internet can be abused for DDoS reflection attacks against third parties.

Please find below a list of affected systems hosted on your network... it goes on.
The notice was issued apparently from 'cert-bund.de'

Brew