A query and response database used for determining the owner of a US registered domain name (.com, for example) or IP address. Whilst the concept was developed with the best of altruistic intentions (such as allowing system administrators to look up and contact other domain name administrators in order to address problems), the system can have nefarious uses - like building email lists for SPAM campaigns. Oline marketers might use a WHOIS database for a number of legitimate reasons, such as; (a) checking who owns a domain that is inactive, perhaps with a view to purchasing it, or (b) as part of a competitor analyse - the registration of particular names might betray future business plans. Note that there is no WHOIS facility available for .uk and other EU domain names as the information is protected by the Data Protection Act in the UK and similar legislation in other EU countries.