Computer worms. Conceptual computer artwork of a globe and computer screens with worm shapes (red) representing computer worm programs. Computer worm programs spread through computer networks like the internet, the global network of computers. Worms, unlike computer viruses, do not run using another program. They run independently and carry out the usually malicious instructions in their program, such as deleting computer data. When replicating, they take up bandwidth, the capacity to transmit data over a network. This can slow down the whole internet. Computer worm programs are considered to be more destructive than computer viruses.