Jump to content

DNS sinkhole

From Wikipedia, the free encyclopedia

A DNS sinkhole, also known as a sinkhole server, Internet sinkhole, or Blackhole DNS[1] is a Domain Name System (DNS) server that has been configured to hand out non-routable addresses for a certain set of domain names. Computers that use the sinkhole fail to access the real site.[2] The higher up the DNS resolution chain the sinkhole is, the more requests will fail, because of the greater number of lower nameservers that in turn serve a greater number of clients. Some of the larger botnets have been made unusable by top-level domain sinkholes that span the entire Internet.[3] DNS Sinkholes are effective at detecting and blocking bots and other malicious traffic.

By default, the local hosts file on a computer is checked before DNS servers, and can be used to block sites in the same way.


Sinkholes can be used both constructively, to contain threats such as WannaCry[4] and Avalanche,[5][6] and destructively, for example disrupting DNS services in a DoS attack.[clarification needed]

DNS sinkholing can be used to protect users by intercepting DNS request attempting to connect to known malicious domains and instead returning an IP address of a sinkhole server defined by the DNS sinkhole administrator.[7] One example of blocking malicious domains is to stop botnets, by interrupting the DNS names the botnet is programmed to use for coordination.[8] Another use is to block ad serving sites, either using a hosts file-based sinkhole[9] or by locally running a DNS server (e.g., using a Pi-hole). Local DNS servers effectively block ads for all devices on the network.[10]


  1. ^ kevross33, pfsense.org (November 22, 2011). "BlackholeDNS: Anyone tried it with pfsense?". Archived from the original on April 15, 2013. Retrieved October 12, 2012.{{cite news}}: CS1 maint: numeric names: authors list (link)
  2. ^ Kelly Jackson Higgins, sans.org (October 2, 2012). "DNS Sinkhole - SANS Institute". Retrieved October 12, 2012.
  3. ^ Kelly Jackson Higgins, darkreading.com (October 2, 2012). "Microsoft Hands Off Nitol Botnet Sinkhole Operation To Chinese CERT". Retrieved September 2, 2015.
  4. ^ Hay Newman, Lily (2017-05-13). "The WannaCry Ransomware 'Kill Switch' That Saved Untold PCs From Harm". Wired. Archived from the original on 2022-06-27. Retrieved 2022-08-19.
  5. ^ Symantec Security Response (December 1, 2016). "Avalanche malware network hit with law enforcement takedown". Symantec Connect. Symantec. Retrieved December 3, 2016.
  6. ^ Europol (December 1, 2016). "'Avalanche' network dismantled in international cyber operation". europol.europa.eu. Europol. Retrieved December 3, 2016.
  7. ^ "DNS Sinkhole". ENISA. Retrieved 2022-08-19.
  8. ^ Hay Newman, Lily (2018-01-02). "Hacker Lexicon: What Is Sinkholing?". Wired. Retrieved 2022-08-19.
  9. ^ Dan Pollock, someonewhocares.org (October 11, 2012). "How to make the Internet not suck (as much)". Retrieved October 12, 2012.
  10. ^ "Turn A Raspberry Pi Into An Ad Blocker With A Single Command". Lifehacker Australia. 2015-02-17. Retrieved 2018-05-06.