Tries to find hostnames that resolve to the target's IP address by querying the online database at http://www.bfk.de/bfk_dnslogger.html. The script is in the 'external' category because it sends target IPs to a third party in order to query their database. SYNTAX: hostmap.prefix: If set, saves the output for each host in a file called '<prefix><target>'. The file contains one entry per line. http.pipeline: If set, it represents the number of HTTP requests that'll be pipelined (ie, sent in a single request). This can be set low to make debugging easier, or it can be set high to test how a server reacts (its chosen max is ignored). http.useragent: The value of the User-Agent header field sent with requests. By default it is ''Mozilla/5.0 (compatible Nmap Scripting Engine http://nmap.org/book/nse.html)''. A value of the empty string disables sending the User-Agent header field. http-max-cache-size: The maximum memory size (in bytes) of the cache.