Do they not? I feel like I read about the FBI foiling plans to blow up this or that multiple times a year.
For example this, which happened in the past month: "FBI arrest man over alleged Amazon centre bomb plot" (https://www.bbc.com/news/technology-56719618)
"He believed that there were 24 buildings that 'run 70% of the internet', including services used by the CIA and FBI, according to a conversation detailed in the criminal complaint against him."