I posted this in GD since there is obviously no factual answer. Also aside from being granted extrajudicial powers, this question is concerned with whether they would use such tactics.
In our post 9/11 world, we know for a fact that international intelligence agencies have gone into override with intelligence gathering. Apparently, dozens of attacks are prevented in Western Europe, the US, Canada, Australia, Hong Kong, Russia (though that can be disputed).
Looking at the history of governments and their specifically the US, no one should be surprised by any unethical actions that are leaked in future decades. We know torture is in Guantanamo Bay for prisoners who haven’t gone through any legal process in any country and some of who are completely innocent, drone strikes kill innocent civilians as shown by Wiki Leaks etc.
What I’m really interested is how often the CIA nabs terrorists with 'social engineering methods. Rather than using physical methods (arrests, executions with chemical/biological means), or electronic methods (hacking electronic devices, wiretap), they get a trusted individual to befriend a suspected criminal and gather intelligence.
Example:* a gender rights terrorist who is part of an extremist form of mens rights activism (20 people). They are plotting to plant a suicide bomber a court in the US where a female teacher is being accused of having sex with a younger boy but getting a light sentence in a few years. They are spread across England, Belgium and New York. Europol hears about this but due to their secretive and paranoid nature, cannot get anything from tapping their communications. No matter how long they listen, the men know they are being watched and are extremely cautious. However, they have heard from reading their manifestos that these men believe that they will get young adult virgin lesbians after blowing themselves up.
Europol shares this with the Americans and they decide what to do.
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Knowing that they don’t have concrete evidence that they are planning attacks but are certain that they have every intention, would the CIA/FBI try and infiltrate the group with two female young agents befriending a member. The hope would be that the group member would be seduced and his defenses would drop thereby revealing the plot.
Do you believe such tactics would ever be used by any intelligence agency?