A network telescope (also known as a ‘packet telescope,’ ‘darknet,’ ‘Internet motion sensor,’ or ‘black hole’) is an Internet system that allows one to observe different large-scale events taking place on the Internet. The basic idea is to observe traffic targeting the dark (unused) address-space of the network.
Since all traffic to these addresses is suspicious, one can gain information about possible network attacks (random scanning worms, and DDoS backscatter) as well as other misconfigurations by observing it.
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The Daily Omnivore 