Directing covert attention to the target location enhances sensitivity, but it is not clear how this enhancement comes about. Knowing that a single spatial frequency channel mediates letter identification, we use the critical-band-masking paradigm to investigate whether covert attention affects the spatial frequency tuning of that channel. We find that directing attention to the target location...

Covert channels use stealth communications to compromise the security policies of systems. They constitute an important security threat since they can be used to exfiltrate confidential data from networks. TCP/IP protocols are used everyday and are subject to covert channels problems. Covert channels are used for the secret transfer of information. Encryption only protects communication from be...

We propose a theoretical framework for a network covert channel based on enumerative combinatorics. It offers protocol independence and avoids detection by using a mimicry defense. Using a network monitoring phase, traffic is analyzed to detect which application-layer protocols are allowed through the firewalls. Using these results, a covert channel is built based on permutations of benign netw...

We report a novel approach for detecting a hostile process extruding data through a covert timing channel. Our method looks for correlations between the timing of network traffic and bit strings in the address space of the suspicious process. Background Covert leakage of sensitive information from governmental or corporate systems remains a significant threat. Intelligent network gateways can c...

We consider a scenario in which K transmitters attempt to communicate covert messages reliably to a legitimate receiver over a discrete memoryless multiple-access channel (MAC) while simultaneously escaping detection from an adversary who observes their communication through another discrete memoryless MAC. We assume that each transmitter may use a secret key that is shared only between itself ...

Cloud computing is becoming increasingly popular because of the dynamic deployment of computing service. Another advantage of cloud is that data confidentiality is protected by the cloud provider with the virtualization technology. However, a covert channel can break the isolation of the virtualization platform and leak confidential information without letting it known by virtual machines. In t...

This paper introduces interference channels, a new kind of covert channel that works by creating external interference on a shared communications medium (such as a wireless network). Unlike previous covert channels, here the covert sender does not need to compromise an authorized sender or require the ability to send messages on the network, but only needs the ability to jam traffic for short i...

This letter studies and compares the physical-layer security approach and the covert communication approach for a wiretap channel with a transmitter, an intended receiver and an eavesdropper. In order to make the comparison, we investigate the power allocation problems for maximizing the secrecy/covert rate subject to the transmit power constraint. Simulation results illustrate that if the eave...