Trojan horse

The Trojan horse was, in the epic poem The Aeneid, a wooden horse presented as gift to the city of Troy during the Trojan War which, when brought inside the city gates, was discovered to hold Greek troops inside. Over time, the term "Trojan horse" has come to mean any seemingly benign object which holds a hidden threat or danger.

T'Ryssa Chen was suspected of being a Trojan horse after being attacked by Borg, and then sent 2000 light years back to Federation space, seemingly unassimilated.