Security measures to prevent thermal imaging intrusion


I am looking to determine the best security measures to prevent unauthorized access to my network by an attacker using thermal imaging through a window/wall. I know there is thermal imaging can that detect subtle enough fluctuations in heat to monitor your keyboard strokes through a wall.

But how sensitive is the detection really?

Is it sensitive enough to detect hand writing as you are writing sensitive information down on paper?

Is there enough heat fluctuations on a monitor between colors to be able to detect information on a monitor?