A difference between a worm and a virus is that _.

Computer worms are similar to viruses in that they replicate functional copies of themselves and can cause the same type of damage. In contrast to viruses, which require the spreading of an infected host file, worms are standalone software and do not require a host program orhuman help to propagate. A virus must attach itself to a program or document and is spread by traveling with the carrier. A worm, however, can travel by itself (Security Awareness: Applying Practical Security in Your World By Mark Ciampa).