If I want to find the leak in my agency, I tell twenty people twenty stories and wait to see which emerges.
If I want to find out who's selling my contact info to spammers, I give every company a different email of mine and check which one gets the spam.
If I want to know who's blackmailing people, I tell each suspect about a different potential victim and watch to see who gets blackmailed next.
How can I refer to this strategy without explaining it?
Disinformation
"Disinformation is intentionally false or inaccurate information that is spread deliberately.[1] It is an act of deception and false statements to convince someone of untruth. Disinformation should not be confused with misinformation, information that is unintentionally false." Quoted from Wikipedia
There was an elaborate program of disinformation in WWII to convince the Germans that the invasion would not be at Normandy, but at Calais. If you like science fiction, see Connie Willis "All Clear", the sequel to "Blackout". Strange, I agree to list SF as a reference, but her depiction of WWII in London and key places in England was extraordinarily well researched.
Moles and other vermin are often caught with bait.
As a noun, bait is
a poisoned lure used in exterminating pests. (definition 2)
an allurement; enticement (definition 3)
As a verb, to bait is
to entice by deception or trickery so as to entrap or destroy (definition 8)
to attract, tempt, or captivate (definition 9)
The fine disinformation answer from @ab2 leans more toward the false intel, while the bait answer leans more toward to catch a mole.
