From the article:
Memex was designed by the Defense Advanced Research Projects Agency It scours the so-called dark net to create data maps of links and patterns
This identifies associations between sites and criminal groups, for example
It follows the announcement of a UK-based unit set up to track down dark net users sharing child pornography over secret networks
Experts will use digital fingerprints left on dark net to hunt paedophiles
Some other sources:
http://www.scientificamerican.com/article/human-traffickers-caught-on-hidden-internet/
http://www.darpa.mil/newsevents/releases/2014/02/09.aspx
Interesting:
The program is specifically not interested in proposals for the following: attributing anonymous services, deanonymizing or attributing identity to servers or IP addresses, or accessing information not intended to be publicly available.
Video:
http://www.cbsnews.com/news/new-search-engine-exposes-the-dark-web/
Somehow I don't believe it is "just" to hunt paedophiles.