DNS sinkhole

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A DNS sinkhole, also known as a sinkhole server, Internet sinkhole, or Blackhole DNS[1] is a DNS server that gives out false information[clarification needed], domain name.

Operation[edit]

A sinkhole is a DNS provider that supplies systems looking for DNS information with false results, allowing an attacker to redirect a system to a potentially malicious destination. DNS sinkholes have also historically been used for non-malicious purposes.

When a computer visits a DNS source to resolve a domain name, the provider will give a result if possible, and if not, it will send the resolution system to a higher-level provider to try again. The higher a DNS Sinkhole is in this chain, the more requests it will receive, the more beneficial effect it will provide.

Network-level disabling[edit]

A sinkhole is a standard DNS server that has been configured to hand out non-routable addresses for all domains in the sinkhole, so that every computer that uses it will fail to get access to the real website.[2] The higher up the DNS resolution chain the sinkhole is, the more requests it will block as it will supply answers to a greater number of lower NS servers that in turn will serve a greater number of clients. Some of the larger botnets have been made unusable by TLD sinkholes that span the entire Internet.[3] DNS Sinkholes are effective at detecting and blocking malicious traffic, and are used to combat bots and other unwanted traffic.

Host-level disabling[edit]

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

Applications[edit]

Sinkholes can be used both constructively, as has been done for the containment of the WannaCry and Avalanche threats,[4] and destructively, for example disrupting DNS services in a DoS attack.

One use is to stop botnets, by interrupting the DNS names the botnet is programmed to use for coordination. The most common use of a hosts file-based sinkhole is to block ad serving sites.[5] Ad serving can also be blocked (e.g., using Pi-hole) using a locally running DNS server on your computer or on your local network effectively blocking Ads for all devices on the network.[6]

References[edit]

  1. ^ kevross33, pfsense.org (November 22, 2011). "BlackholeDNS: Anyone tried it with pfsense?". Retrieved October 12, 2012.
  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. ^ 262588213843476. "Wannacrypt0r-FACTSHEET.md". Gist.
  5. ^ Dan Pollock, someonewhocares.org (October 11, 2012). "How to make the Internet not suck (as much)". Retrieved October 12, 2012.
  6. ^ "Turn A Raspberry Pi Into An Ad Blocker With A Single Command". Lifehacker Australia. 2015-02-17. Retrieved 2018-05-06.