Examples of lost security when integrating (secure) SW

I just had a discussion with my colleagues regarding problems with
security in larger systems that are composed by combining
modules/components that individually are secure. Both my gut and sources
I have consulted says this is the case. However, I haven't been able to
find any examples of when this has happened!

Bruce Schneier spends a few pages in Secrets & Lies on the subject,
without offering any examples of what can happen. I seem to remember
some talk on a conference (was it Usenix?) a few years ago__I never
attended it but I read the abstract of the papers/talks--where a talk on
security mentioned a case where the combination of two security features
effectively cancelled each other.

Can anyone offer any more concrete examples, ideally not only academic
ones?

/M

-- 
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Magnus Therning                 Philips Research Laboratories Eindhoven
Phone: +31 40 2745179           (OpenPGP: 0x4FBB2C40)

Some operating systems are called 'user friendly', Linux however is
'expert friendly'.

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