Insidious
Insidious adj. 1. Working or spreading harmfully in a subtle or stealthy manner: insidious rumors; an insidious disease. 2. Beguiling but harmful; alluring: insidious pleasures.

Insidious adj. 1. Working or spreading harmfully in a subtle or stealthy manner: insidious rumors; an insidious disease. 2. Beguiling but harmful; alluring: insidious pleasures.