Covert Channels in Computer Networks
The idea behind covert channels is to hide
'illegitimate' communication channels in 'legitimate' communication
channels so that any observer is unaware of the hidden
communication.The problem was first published by Lampson in 1973. He defined covert channels as "channels, [...] not intended for information transfer at all". In 1985 the US DoD
defined the concept of covert channels as follows: "A covert channel is
any communication channel that can be exploited by a process to
transfer information in a manner that violates the system'ssecurity policy".
Covert channels in general have been the topic of research for over
three decades. More recently covert channels have been researched in
computer network protocols. The idea was initially proposed by Girling in
1987 and illustrated with some examples. Some research was done during
the 90's but there are only few publications. Only recently (since
2002) this topic seemed to have sparked significant interest
in the networking and security research community.
Covert channels are part of the wider area of information hiding. A
closely related topic is steganography (meaning covered writing in
greek), which is the hiding of information in audio, pictures and
video. Hence some people also refer to covert channels in network
protocols as protocol or Internet steganography.
Subliminal channels proposed by Simmons in 1983 are covert channels embedded in digital signatures.
page focusses on covert channels in
computer network protocols but also contains some information about
subliminal channels, covert channels in general, steganography etc. I
started this page when I did the literature survey for my PhD. Many
thanks to a number of people who contributed by sending me
Publications on Covert Channels in Computer Network Protocols
Publications on Subliminal Channels
More general publications on Covert Channels
Covert Channels in Computer Networks Tools
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