On a Friday in February, a visitor to the website 4chan posted child porn photos to the “international” channel. 4chan may be notorious for the offensive images that get posted there, but it turns out there are limits even on that free-wheeling board. According to a police affidavit, 4chan flagged the post, recorded the Internet Protocol (IP) address associated with the user who posted it, and reported it to the National Center for Missing and Exploited Children. The Center passed the tip along to the feds, who forwarded it to the Seattle Police Department, where it landed on the desk of Detective Daljit Gill.
The ultimate fate of that tip, according to a new white paper from the digital civil liberties group Electronic Frontier Foundation, reveals in part why IP addresses can be unreliable pieces of evidence that are misused by police and the courts.