Sinkhole divers. Some of the most spectacular are the Zacatón cenote in Mexico (the world's deepest water-filled sinkhole), the Boesmansgat sinkhole in South Africa, Sarisariñama tepuy in Venezuela, the Sótano del Barro in Mexico, and in the town of Mount Gambier, South Australia. Sinkholes that form in coral reefs and islands that collapse to enormous depths are known as blue holes and often become popular diving spots. Large and visually unusual sinkholes have been well-known to local people since ancient times. Nowadays sinkholes are grouped and named in site-specific or generic names. Some examples of such names are listed below. The
DNS sinkhole 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. Ad serving can also be blocked using a locally running DNS server on your computer or on your local network effectively blocking Ads for all devices on the network. DNS sinkhole A DNS sinkhole, also known as a sinkhole server, Internet sinkhole, or Blackhole DNS is a DNS server that gives out false information, to prevent the use of a domain name.