The ones working for west Germany, as well as America weren't hiding, they were useful. Their targets were the one who were useless alive for anything other than getting revenge against.

The key is they had a good excuse to build a highly effective surveillance and infiltration system. It also was/is skilled at getting their hands dirty on foreign soil, while keeping the mess contained. At the time, they have a worthy target. As time went on, the number of targets dropped. The system in place was then turned to other uses.