Let me give you a glimpse of my opinion, about NATO hidden operatives, against the russian embassy. Besides traffic signs with microphones and the most closed antennas, one of the most important spot, is the Mail Office (Correios), less then 30 meters. The internet sniffing comes trought that office, to search either for communications, and specific banking transferences. So, let me start.

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The technical aspects, are using SVR "sites" locations signals, this is the russian equipmment

https://www.irz.ru/products/15/134.htm

This is NATO machine for surveillance  -  

HP 831065-S01 Smart Buy Ml30 Gen9 E3-1230V5 4G Us Svr

https://www.newegg.com/Product/Product.aspx?Item=2NS-0006-0JN60

This is how the secret service, here at Portugal, use the national hidden video surveillance, trought the SVR signals of the train network