The Internet has become an attractive form of communication for criminals because of the anonymity it provides. In order to pursue these criminals, investigators must also lurk on message boards and chat rooms while attempting to disguise their identities as law enforcement officers. Investigators generally use either active or passive techniques to root out online criminals. Passive techniques involve obtaining information from open sources on the Internet, such as from newsgroups or Web sites, name service lookup, WHOIS queries, and GeoLookup queries. Active investigation techniques, such as traceroute and ping methods, allow investigators to trace the physical path taken by Internet data back to the point of origin. Active techniques are riskier for investigators to use because they can be easily identified by a knowledgeable target. Criminals can also use these methods against law enforcement officers, identifying the location and owner of the computer being used by the officer. Creating an undercover identity is critically important for Internet investigators. Guidelines for protecting the online identity of investigators are offered and include obtaining a non-attributable credit card and choosing an ambiguous username.