Hello there! We are conducting a survey to better understand the user experience in making a first edit. If you have ever made an edit on Gamepedia, please fill out the survey. Thank you!
Countermeasures, or at least the physical kind, are considered a type of self-propelled weapon, though their purpose is defensive.
The only known physical countermeasure is a chaff dispenser, which presumably confuses missile guidance systems when released.