Stuxnet is classified as a computer worm because

it worked its way into an existing but vulnerable program and then waited in secret to be activated so it could spread

it actively sought to replicate and spread itself without the need for any other programs to act as hosts for it$.$

it crawled from one end of the network it was attacking to the other end in order complete its job.

it was the software equivalent of a human mole, so it was named after a creature that travels underground.

it was used as the bait in a phishing attack to hook unsuspecting users.