Content Filtering and Security
Ed Felten

http://www.freedom-to-tinker.com/?p=854

Buggy security software can make you less secure. Indeed, a growing number
of intruders are exploiting bugs in security software to gain access to
systems. Smart system administrators have known for a long time to be
careful about deploying new ³security² products.

A company called Audible Magic is trying to sell ³content filtering² systems
to universities and companies. The company¹s CopySense product is a computer
that sits at the boundary between an organization¹s internal network and the
Internet. CopySense watches the network traffic going by, and tries to
detect P2P transfers that involve infringing content, in order to log them
or block them. It¹s not clear how accurate the system¹s classifiers are, as
Audible Magic does not allow independent evaluation. The company claims that
CopySense improves security, by blocking dangerous P2P traffic.

It seems just as likely that CopySense makes enterprise networks less
secure. CopySense boxes run general-purpose operating systems, so they are
prone to security bugs that could allow an outsider to seize control of
them. And a compromised CopySense system would be very bad news, an ideal
listening post for the intruder, positioned to watch all incoming and
outgoing network traffic.

How vulnerable is CopySense? We have no way of knowing, since Audible Magic
doesn¹t allow independent evaluation of the product. You have to sign an NDA
to get access to a CopySense box.

This in itself should be cause for suspicion. Hard experience shows that
companies that are secretive about the design of their security technology
tend to have weaker systems than companies that are more open. If I were an
enterprise network administrator, I wouldn¹t trust a secret design like
CopySense.

Audible Magic could remedy this problem and show confidence in their design
by lifting their restrictive NDA requirements, allowing independent
evaluation of their product and open discussion of its level of security.
They could do this tomorrow. Until they do, their product should be
considered risky.



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