Abstract. The exploration of advanced covert timing channel design is important to understand and defend against covert timing channels. In this paper, we introduce a new class of covert timing channels, called model-based covert timing channels, which exploit the statistical properties of legitimate network traffic to evade detection in an effective manner. We design and implement an automated framework for building model-based covert timing channels. Our framework consists of four main components: filter, analyzer, encoder, and transmitter. The filter characterizes the features of legitimate network traffic, and the analyzer fits the observed traffic behavior to a model. Then, the encoder and transmitter use the model to generate covert traffic and blend with legitimate network traffic. The framework is lightweight, and the overhead induced by model fitting is negligible. To validate the effectiveness of the proposed framework, we conduct a series of experiments in LAN and WAN environments. The experimental results show that model-based covert timing channels provide a significant increase in detection resistance with only a minor loss in capacity.
Abstract-The detection of covert timing channels is of increasing interest in light of recent exploits of covert timing channels over the Internet. However, due to the high variation in legitimate network traffic, detecting covert timing channels is a challenging task. Existing detection schemes are ineffective at detecting most of the covert timing channels known to the security community. In this paper, we introduce a new entropybased approach to detecting various covert timing channels. Our new approach is based on the observation that the creation of a covert timing channel has certain effects on the entropy of the original process, and hence, a change in the entropy of a process provides a critical clue for covert timing channel detection. Exploiting this observation, we investigate the use of entropy and conditional entropy in detecting covert timing channels. Our experimental results show that our entropybased approach is sensitive to the current covert timing channels and is capable of detecting them in an accurate manner.
The detection of covert timing channels is of increasing interest in light of recent practice on the exploitation of covert timing channels over the Internet. However, due to the high variation in legitimate network traffic, detecting covert timing channels is a challenging task. The existing detection schemes are ineffective to detect most of the covert timing channels known to the security community. In this paper, we introduce a new entropy-based approach to detecting various covert timing channels. Our new approach is based on the observation that the creation of a covert timing channel has certain effects on the entropy of the original process, and hence, a change in the entropy of a process provides a critical clue for covert timing channel detection. Exploiting this observation, we investigate the use of entropy and conditional entropy in detecting covert timing channels. Our experimental results show that our entropy-based approach is sensitive to the current covert timing channels, and is capable of detecting them in an accurate manner.
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