For more than four days, a server at the very core of the Internet’s domain name system was out of sync with its 12 root server peers due to an unexplained glitch that could have caused stability and security problems worldwide. This server, maintained by Internet carrier Cogent Communications, is one of the 13 root servers that provision the Internet’s root zone, which sits at the top of the hierarchical distributed database known as the domain name system, or DNS.

Source: Technology Lab – Ars Technica