Distinguish between safe and intrusive NSE scripts and give an example usage scenario for each.

• A. Safe NSE scripts are non-disruptive and focus on non-intrusive checks like http-title.
• B. Safe NSE scripts always require root privileges.
• C. Intrusive NSE scripts probe vulnerabilities or misconfigurations and may disrupt service; use in controlled environments.
• D. All NSE scripts are intrusive by design.

Answer: (C)

NSE scripts differ in how much they might affect the target. Some are designed to be safe and non-disruptive, simply gathering information or verifying things without touching the service beyond reading data. Intrusive scripts go further: they probe for vulnerabilities or misconfigurations and can disrupt or destabilize a service, so they should only be used where you have explicit permission and in controlled environments.

That distinction is why the statement about intrusive scripts is the most accurate: they probe vulnerabilities or misconfigurations and may disrupt service, so they’re appropriate only in a lab or other controlled, authorized testing scenario. An example of a safe usage is running a script that reads the HTTP title to confirm what service is listening on a port, which provides information without affecting the service. An example of an intrusive usage is running a vulnerability-focused script in a test network to detect known flaws—procedures like this carry a risk of disruption and must be done with consent and proper safeguards.

Other points to note: not all safe scripts require root privileges, and not all NSE scripts are intrusive; some are explicitly designed to be non-disruptive.