The term Trojan horse has come to refer to subversion introduced from the outside.

From Britannica:

The Trojan horse, a huge hollow wooden horse constructed by the Greeks to gain entrance into Troy during the Trojan War. The horse was built by Epeius, a master carpenter and pugilist. The Greeks, pretending to desert the war, sailed to the nearby island of Tenedos, leaving behind Sinon, who persuaded the Trojans that the horse was an offering to Athena (goddess of war) that would make Troy impregnable. Despite the warnings of Laocoön and Cassandra, the horse was taken inside the city gates. That night Greek warriors emerged from it and opened the gates to let in the returned Greek army.