Webmasters should strive to ensure that they do not become a part of the exchange of child pornography. Webmasters, particularly those who offer free website hosting, may find their generosity exploited by pornographers. Webmasters can search the files on their machines for words which indicate that a site may contain child pornography .
Webmasters can also watch for unusually large activity of .jpg files, with particular names .
There are also scans which are identified by an abbreviation of the pornographic magazine from which they originated. If a new site suddenly has a lot of traffic in image files, and the files disproportionately start with those prefixes, the site should be investigated. I don't know enough about the industry, and my list would be misleading. I would hope that the FBI or Customs would cooperate with any webmaster interested in implementing automatic detection, by providing a list of the most commonly encountered filenames and referral sources.