End-to-end packet delay and loss behavior in the internet
SIGCOMM '93 Conference proceedings on Communications architectures, protocols and applications
Tor: the second-generation onion router
SSYM'04 Proceedings of the 13th conference on USENIX Security Symposium - Volume 13
Language identification of encrypted VoIP traffic: Alejandra y Roberto or Alice and Bob?
SS'07 Proceedings of 16th USENIX Security Symposium on USENIX Security Symposium
Spot Me if You Can: Uncovering Spoken Phrases in Encrypted VoIP Conversations
SP '08 Proceedings of the 2008 IEEE Symposium on Security and Privacy
Nmap Network Scanning: The Official Nmap Project Guide to Network Discovery and Security Scanning
Nmap Network Scanning: The Official Nmap Project Guide to Network Discovery and Security Scanning
Detailed analysis of Skype traffic
IEEE Transactions on Multimedia
On the risks of serving whenever you surf: vulnerabilities in Tor's blocking resistance design
Proceedings of the 8th ACM workshop on Privacy in the electronic society
Phonotactic Reconstruction of Encrypted VoIP Conversations: Hookt on Fon-iks
SP '11 Proceedings of the 2011 IEEE Symposium on Security and Privacy
Telex: anticensorship in the network infrastructure
SEC'11 Proceedings of the 20th USENIX conference on Security
BridgeSPA: improving Tor bridges with single packet authorization
Proceedings of the 10th annual ACM workshop on Privacy in the electronic society
Cirripede: circumvention infrastructure using router redirection with plausible deniability
Proceedings of the 18th ACM conference on Computer and communications security
Proceedings of the 2012 ACM conference on Computer and communications security
SkypeMorph: protocol obfuscation for Tor bridges
Proceedings of the 2012 ACM conference on Computer and communications security
StegoTorus: a camouflage proxy for the Tor anonymity system
Proceedings of the 2012 ACM conference on Computer and communications security
CensorSpoofer: asymmetric communication using IP spoofing for censorship-resistant web browsing
Proceedings of the 2012 ACM conference on Computer and communications security
The Parrot Is Dead: Observing Unobservable Network Communications
SP '13 Proceedings of the 2013 IEEE Symposium on Security and Privacy
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In response to increasingly sophisticated methods of blocking access to censorship circumvention schemes such as Tor, recently proposed systems such as Skypemorph, FreeWave, and CensorSpoofer have used voice and video conferencing protocols as "cover channels" to hide proxy connections. We demonstrate that even with perfect emulation of the cover channel, these systems can be vulnerable to attacks that detect or disrupt the covert communications while having no effect on legitimate cover traffic. Our attacks stem from differences in the channel requirements for the cover protocols, which are peer-to-peer and loss tolerant, and the covert traffic, which is client-proxy and loss intolerant. These differences represent significant limitations and suggest that such protocols are a poor choice of cover channel for general censorship circumvention schemes.