Tips? Mistakes? Customs officers getting a funny feeling about something in their bags? Google searches? Purchases of stuff to make explosives with? Surveillance? The child tells their parents some creepy guy offered them a thousand Euros? Do you think intelligence agencies don't already look for this sort of thing?
https://en.wikipedia.org/wiki/Operation_Pastorius has a nice example of how this works that doesn't even rely on modern surveillance tech. They accomplished zero sabotage, and six were put to death for it.
> Even before the mission began, it was in danger of being compromised, as George Dasch, commander of the team, left confidential documents on a train, and one of the agents, while drunk, announced to patrons in a Paris tavern that he was a secret agent.
> Immediately upon reaching the beach, at around 30 minutes past midnight the saboteurs were discovered amidst the dunes by unarmed Coast Guard Seaman John C. Cullen, who was accosted by Dasch and offered a bribe of $300. (Cullen had been shortchanged, the money only amounted to $260.) Cullen feigned cooperation but reported the encounter.
> Additional breaches of secrecy occurred; Kerling had boasted to a colleague about their mission, and in Chicago, Herbert Haupt had asked his father to buy him a sports car claiming he needed it while traveling on business for the German government.
Any operation involving humans has opportunities for fuckups.
Why would I presume this to be any more accurate than "can't arrest somebody for a sabotage without letting him to execute the deed" was?
If sabotage is so easy to perform without detection, why aren't motivated actors doing more of it? It's certainly not a lack of motive at play, here.
Humans make mistakes. The saboteur can't afford any. The cops only have to get lucky once. And these are the folks who mix up "SIM card" with the game "The Sims" (https://www.washingtonpost.com/video-games/2022/04/26/russia...).
https://en.wikipedia.org/wiki/Double-Cross_System
> After the war, it was discovered that all the agents Germany sent to Britain had given themselves up or had been captured, with the possible exception of one who committed suicide.
Not a single successful agent in five years of war.
Do you think they publicly announce every one they catch? Or that none are ever deterred?
> It turns out that one can't see into a mind of other person.
And yet, we manage to catch people planning things, because sabotage requires more than just a thought.