Abstract: Downloading an authoritative zone file and performing searches within the zone file can identify all of the domain names registered to an entity. A method of identifying all of the domain names registered to an entity may including downloading a root zone file from a registry or from a root server and storing the root zone file as a text file with alphanumeric character strings associating each domain name with a registrar and at least one domain name server. A search characteristic is established corresponding to a character string comprising a significant part of one of the entity's domain names. A string search is performed in the download root zone file for the search characteristic to identify one or more domain names matching the search characteristic, as well as a registrar corresponding to the matching domain name and at least one domain name server associated with the matching domain name in the downloaded root zone file.