Which statement correctly describes the role of external providers in defending against DoS as described in the material?

• A. Assistance from ISPs and upstream providers is often required.
• B. Assistance from ISPs is never required.
• C. End users handle it alone.
• D. Antivirus software alone suffices.

Answer: (A)

Defending against DoS often requires help from external networks because huge floods can saturate the victim’s bandwidth before any internal defenses can react. External providers like ISPs and upstream networks see traffic at a larger scale, have dedicated scrubbing centers, and can filter or redirect attack traffic before it reaches the target. They can implement edge filtering, rate limiting, or even null routes to drop malicious traffic and then forward clean traffic to the victim. This collaboration is why the statement that assistance from ISPs and upstream providers is often required best describes the defense approach.

End users alone typically can’t handle large DoS floods, since the volume can overwhelm consumer or enterprise connections. Antivirus software doesn’t address network floods at all, so it isn’t sufficient for DoS protection.