Which method is used to thwart DoS attacks by dropping all IP packets from an attacker?

• A. ICMP echo
• B. P2P redirect
• C. None of the above
• D. Black holing

Answer: (D)

Dropping attacker traffic through blackhole routing is a fast, blunt way to mitigate a DoS flood by ensuring all packets from the attacker are discarded before they consume bandwidth or processing power. In practice, networks direct the unwanted traffic toward a null interface or “black hole” so the packets are dropped, often using dynamic routing (like BGP) to announce a null route for the attacker’s source or target prefix. This stops the flood quickly and can protect other users and services, though it can also affect legitimate traffic if not carefully scoped, so it’s typically a last-resort or targeted measure.

The other options don’t accomplish this: an ICMP echo is simply a diagnostic ping and does not remove or drop traffic as a defense; a P2P redirect is a routing technique to alter paths and isn’t meant to discard traffic; and “none of the above” isn’t correct because black holing directly fits the described method.