Chapter 23: Problem 16

What are covert channels? Give an example of a covert channel.

Short Answer

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A covert channel is a type of communication that enables information transfer that can potentially violate a system's security policies. An example of covert channels can be the use of a shared resource (like the wallpaper color in a multi-user OS) where changes in the resource's state can be used to convey information.

Step by step solution

Defining Covert Channel

Covert channels are a type of communication pathway that enables two parties to exchange information in a way that violates the system's security policies. This type of communication is usually done in a concealed or 'covert' way which is not designed to be used for communication, making it challenging for system administrators to detect.

Understanding Covert Channels

Covert channels can be divided into two types: storage channels and timing channels. Storage channels involve the direct or indirect writing of a storage location by one process and the direct or indirect reading of the storage location by another process. Timing channels involve one process signaling information to another by modulating its own use of system resources (like CPU time) in a way that affects the real response time observed by the second process.

Example of a Covert Channel

Let's look at an example of a storage covert channel: Consider a multi-user operating system where the color of the wallpaper is visible to all users. If one user (the sender) changes the color of the wallpaper, the other user (the receiver) can see the change. This method can be used to send binary messages: for example, a red wallpaper could represent '1' and a blue wallpaper could represent '0'. This information exchange is a form of a covert channel since it's carrying on without the system administrator's knowledge and it's manipulating a feature (wallpaper color) in an unintended way to enable communication.

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What are covert channels? Give an example of a covert channel.

Short Answer

Step by step solution

Defining Covert Channel

Understanding Covert Channels

Example of a Covert Channel

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