An attacker tries to gain knowledge about which communication protocols are used and how, looking for manners to exploit them. This can be executed intercepting, recording, and analyzing the signal to extract as more information as possible on the communication protocols. For example, different protocols can apply SDLS security to a part of the services. Optical link can be used for satellite feeder and intersat links, for some special payloads, or for deep space communications (availability problem caused by clouds should be considered if the receiver is on the Earth). If the downlink signal is sent by a far spacecraft, the beam covers a large ground area on the Earth, and the possible scanning area is extended. Receiving a satellite signal is simple and cheap, various open-source projects exist, e.g., NyanSat. [1] [2]