You do hear about attacks that have been prevented. Here's one recent example. https://www.bbc.co.uk/news/uk-england-tyne-51022706 https://www.bbc.co.uk/news/u

You do hear about attacks that have been prevented. Here's one recent example. https://www.bbc.co.uk/news/uk-england-tyne-51022706 https://www.bbc.co.uk/news/uk-england-tyne-51022706 But don't forget that places like GCHQ do not release information, so it would be very unusual to get "GCHQ helped identify these suspects". Here's one example where the GCHQ link was made clear (in news reporting), and it's pretty extreme. https://en.m.wikipedia.org/wiki/Matthew_Falder https://en.m.wikipedia.org/wiki/Matthew_Falder