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DNS tunnels are network covert channels that allow
the transmission of arbitrary data using the DNS infrastructure.
Users can use such tunnels to hide their communication sessions
in order to bypass local security and accounting policies. Hence,
it is important that we investigate the viability and performance
of DNS tunneling. Our results show that clients can obtain up
to 110 KB/s in throughput, and delays as low as 150ms. These
results, however, incur very high overheads. In the worst case,
clients generate up to 2000% more traffic!
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