Sexually explicit webcam material proved to be a particular problem for GCHQ, as one document delicately put it: "Unfortunately … it would appear that a surprising number of people use webcam conversations to show intimate parts of their body to the other person. Also, the fact that the Yahoo software allows more than one person to view a webcam stream without necessarily sending a reciprocal stream means that it appears sometimes to be used for broadcasting pornography."
The document estimates that between 3% and 11% of the Yahoo webcam imagery harvested by GCHQ contains "undesirable nudity". Discussing efforts to make the interface "safer to use", it noted that current "naïve" pornography detectors assessed the amount of flesh in any given shot, and so attracted lots of false positives by incorrectly tagging shots of people's faces as pornography.
UK spy agency intercepted webcam images of millions of Yahoo users [Spencer Ackerman and James Ball/The Guardian]