This is the 17034th most frequent Russian word.
спецслужба
"Спецслужба" means "special service" or "intelligence agency."
Here, 'спецслужбы' refers to intelligence agencies or special services responsible for national security and intelligence activities.
Спецслужбы разоблачили опасную организацию.
The intelligence services exposed a dangerous organization.
In this case, 'спецслужбах' (prepositional case) is used to indicate a career or involvement within these agencies.
Он работал в спецслужбах много лет.
He worked in the intelligence services for many years.
Here, 'спецслужбы' (genitive case) denotes a specific intelligence service belonging to a neighboring country.