Which of these is a feature of a stealth virus?

A stealth virus is designed specifically to avoid detection by antivirus programs and other security measures. This feature makes it particularly insidious, as it can operate in the background without raising alarms, allowing it to infect systems and spread more effectively than other types of malware. The ability of the stealth virus to remain hidden enables it to collect sensitive information or perform harmful actions without the user or security software being aware of its presence.

In contrast, the other options do not accurately characterize the nature of a stealth virus. For instance, noticeable slowdowns are more often associated with certain types of malware that consume system resources rather than with stealth viruses, which aim to minimize their impact on system performance to avoid detection. User intervention is typically a characteristic of other virus types that require a user to execute a file or take a specific action for the virus to activate, which is not a defining trait of a stealth virus. Lastly, while some viruses may target non-system files, stealth viruses can affect any files or data they come into contact with, including system files, depending on their design and objectives.