Final answer:
A virus scanner can work by comparing files against a list of known virus profiles, blocking files that copy themselves, blocking all unknown files, or looking at files for virus-like behavior.
Step-by-step explanation:
A virus scanner can work by comparing files against a list of known virus profiles, by blocking files that copy themselves, by blocking all unknown files, or by looking at files for virus-like behavior.
For example, when a virus scanner compares files against a list of known virus profiles, it checks if the contents of the file match any known patterns of viruses. If there is a match, the file is flagged as a potential virus. Similarly, a virus scanner can block files that copy themselves by detecting if a file tries to create multiple copies of itself.
Overall, virus scanners use various techniques to identify and block viruses, ensuring the protection of computer systems.