http://arstechnica.com/tech-policy/2014/05/houseguest-downloads-child-porn-cops-show-up/good to see organisations dealing with this kind of thing, shame for the householders though.
Do you really know how your various friends, relations, acquaintances, and hangers-on plan to use your Internet connection when they drop by and ask for "the Wi-Fi password"? Unlikely—and yet anything that they do illegally through your home network can bring cops to your door with search warrants, asking tough questions about child pornography.
Case in point: Marin County, California, just north of San Francisco's Golden Gate Bridge. Local police in Marin communities like Novato are members of the regional Internet Crimes Against Children (ICAC) task force, and as such they participate in the common law enforcement practice of monitoring peer-to-peer file-sharing networks for possible child pornography files. In September 2013, Novato detective Amy Yardley was looking for such files being traded from Marin County IP addresses, and she scored a hit on the Ares network with a suspicious file downloaded by a Sausalito Internet subscriber.
Yardley passed the tip to the Sausalito Police Department, where detective Brian Mather obtained a search warrant for the subscriber's address. He showed up at the house with a search team but couldn't find any child pornography within. The home's residents, no doubt unnerved by both the search and the charge behind it, pleaded their innocence and gave Mather a complete list of all houseguests who had used their wireless network in recent months.
Investigating this list took months, but Mather eventually developed a suspect: Mark Magner, age 32, from nearby San Rafael. Police then searched Magner's home and seized his computer. A forensic examination of the machine turned up "multiple videos and pictures that depicted juveniles and children involved in sexual acts," in the words of a police department press release.
Mather called Magner in to the Sausalito police headquarters on April 22, told Magner what had been found on his computer, and arrested him. On May 9, the Marin County District Attorney filed charges in state court, accusing Magner of one count of "possession or control of child pornography." Magner is scheduled to enter a plea at a hearing next week
