Black-bag

Watergate turned out to be a black-bag operation by former CIA employees.

Source: wiktionary

Holden's SEAL training had covered clandestine penetrations, but never black-bag jobs

Source: wiktionary

Con Keeler was past his fortieth birthday and a veteran of more black-bag jobs than he could count.

Source: wiktionary

In an interesting coda that perhaps presaged the black-bag jobs of the Watergate era, an unknown person or persons broke into Dr. Parr's office on New York's Forty-second street in 1926, gained access to the safe, and stole President Grant's, Mrs. Grant's, and President Chester Arthur's dentures.

Source: wiktionary