DNS

Network 'address book', the way sites and systems are located

The DNS system is a core part of the internet and most private networks. It is essentially an address book mapping the names of computers or websites with the IP addresses which uniquely identify them and enable them to be contacted.

Networked computers are given a specific DNS server, which they query whenever a website or other host is needed. The DNS server returns the IP address corresponding to the requested name, which it may have cached in its own database or may need to find by querying another DNS server higher up the chain. The IP address then allows the computer to contact the system it wants.

DNS is often manipulated by malware and cybercriminals, for example by adjusting the hosts file to block access to security resources or for pharming purposes.