Sentence:  Using what the bureau calls a "<WSD>False Flag</WSD>" operation, F.B.I. agents posing as Russian intelligence officers contacted Mr. Pitts in August 1995, long after it believed he had ceased his spying activities, and feigned interest in reactivating him as a means of confirming his spying activities and determining how much information he may have provided to Moscow. 
Meaning of the word marked with <WSD> tags:  A diversionary or propaganda tactic of deceiving an adversary into thinking that an operation was carried out by another party.