可以通过shadowserver来查看开放的mdns（用以反射放大攻击）——中国的在 https://mdns.shadowserver.org/workstation/index.html

Open mDNS Scanning Project

 来自：https://mdns.shadowserver.org/

If you are looking at this page, then more than likely, you noticed a scan coming from this server across your network and/or poking at Multicast DNS (mDNS).

The Shadowserver Foundation is currently undertaking a project to search for publicly accessible devices that have the mDNS service accessible and answering queries. The goal of this project is to identify devices with an openly accessible mDNS service and report them back to the network owners for remediation.

These devices have the potential to be used in UDP amplification attacks in addition to disclosing large amounts of information about the system and we would like to see these services made un-available to miscreants that would misuse these resources.

Servers that are configured this way have been incorporated into our reports and are being reported on a daily basis.

Information on UDP-based amplification attacks in general can be found in US-CERT alert TA14-017A at: https://www.us-cert.gov/ncas/alerts/TA14-017A.

Methodology

We are querying all computers with routable IPv4 addresses that are not firewalled from the internet on port 5353/udp with a dns query for "_services._dns-sd._udp.local" and parsing the response. If we find that the "_workstation._tcp.local" or "_http._tcp_local" services are being advertised, we follow up with queries to services to see if they are accessible and exposing information. We intend no harm, but if we are causing problems, please contact us at dnsscan [at] shadowserver [dot] org

If you would like to test your own device to see if mDNS is accessible, run the command "dig @[IP] -p 5353 -t ptr _services._dns-sd._udp.local". If the mDNS service is accessible, you should see a list of services that are being advertised in the ANSWER section of the dig response.

Whitelisting

To be removed from this set of scanning you will need to send an email to dnsscan [at] shadowserver [dot] org with the specific CIDR's that you would like to have removed. You will have to be the verifiable owner of these CIDR's and be able to prove that fact. Any address space that is whitelisted will be publicly available here: https://mdns.shadowserver.org/exclude.html

Useful Links

• Blog Summary: http://blog.shadowserver.org/2014/03/28/the-scannings-will-continue-until-the-internet-improves/
• Get reports on your network: https://www.shadowserver.org/wiki/pmwiki.php/Involve/GetReportsOnYourNetwork
• Current Whitelist: https://mdns.shadowserver.org/exclude.html

Scan Status

Statistics on current run