What characteristic does a 'virus' have compared to a 'worm'?

A virus is characterized by its ability to attach itself to programs or files and requires a host program to execute. This means that a virus will typically insert itself into executable files, and when that program is run, the virus activates and can begin its malicious activity. This attachment is a fundamental aspect of how viruses propagate and spread, setting them apart from worms, which are standalone malware that can replicate and spread independently without needing to attach to a host.

Regarding the other options, a virus does not inherently have the ability to access the internet on its own, as it requires a host program to run. Additionally, unlike worms, which can replicate and spread on their own, viruses rely on user action to propagate; they do not replicate independently. The statement concerning harm comparison is also not accurate because both viruses and worms can cause significant damage depending on their nature and purpose.