Cruise Missiles are long-range, fire-and-forget weapons that can find the target on their own. Like all artillery-type units, Cruise Missiles have no attack or defense values, only bombardment.
A city must have Aluminum in its Strategic Resource box to build Cruise Missiles.
Civilopedia Entry
One of the most effective weapons in modern military arsenals is the cruise missile. The AGM-86 and the Tomahawk can be launched against a strategic target hundreds of miles away, traveling low to avoid radar and other means of detection, and hitting their target with unnerving accuracy. They can also be used against short-range, tactical targets such as ships. In this role, it is often possible for a single, one million dollar missile to seriously damage or even destroy 80 million dollar warships.