Richard Clayton of
the University of Cambridge’s computer science labs is here with us
today at the Berkman Center as a participant in our luncheon
series.  He describes his scholarly efforts focused on BT
(Britain’s largest telecommunications provider) and its blocking
program:

“I’ve been looking at BT’s CleanFeed system (it’s [sic] proper name is the BT
Anti-Child-Abuse Initiative). This was designed to be a low cost, but
highly accurate, system for blocking ‘child pornography’. At first
sight it is significant improvement upon existing schemes. However,
CleanFeed derives its advantages from employing two separate stages,
and this hybrid system is thereby made more fragile because
circumvention of either stage, whether by the end user or by the
content provider, will cause the blocking to fail.”  Mr. Clayton
notes that there are lots of ways to break the system.  His fear,
among other things, is that the BT approach may make it easier for
those seeking to access child pornography to find a complete listing of
all known child pornography.  A recent paper on this score is here.

His research is important insofar as it helps us to understand the way
that “friendly country” filtering works.  In this case, BT is using filtering techniques to block child pornography from
viewing.  The study of how this blocking takes place is
instructive both to those who are seeking to fight the evils of child
pornography as well as those seeking to understand how blocking does
and might work in regimes that do more blocking than just child
pornography, as we and our partners do in the OpenNet Initiative.