🚀 go-pugleaf

In article <1992Aug20.214220.22820@cbnewsl.cb.att.com>, fec@cbnewsl.cb.att.com (f.e.carey) writes:

|> 
|> If file permission settings prevent me from reading the daily 
|> files that contains records of production defects in the factory,
|> the access controls forbiding such access could be
|> said to be functioning.  Yet if I am able to determine
|> the size of the files I can infer information about
|> defect rates.  In such a case there would seem to be
|> no "sending process". 
|> Does such a scenario qualify as a covert channel?

There are two potential security problems here.  First, the size of 
the file could imply the defect rate.  This is an example (albeit
a strange example) of the statistical database inference problems
that Dorothy Denning has written extensively about.

There is a second problem that is a covert channel, namely that
a Trojan horse program could modulate the size of the file (or
files) to encode information.  This is a covert channel.

|> 
|> Another scenario: If I've being held incommunicado in a
|> building and denied access to phones, mail, etc. and I am 
|> able to signal out a message using the venetian blinds, 
|> Have I utilized a covert channel?

Yes - in fact, the classic example of a covert channel is a POW
banging on the walls to communicate with other POWs.