Which technique involves sending messages with a spoofed source IP address to gain unauthorized access?

• A. Spoofing
• B. Phishing
• C. Brute Force
• D. Sniffing

Answer: (A)

IP spoofing involves forging the source IP address in messages so they appear to come from another machine. By sending packets with a spoofed address, an attacker can exploit trust based on where a message seems to originate, potentially slipping past IP-based access controls and gaining unauthorized access to systems or services. The crucial idea is that the recipient can be misled about who sent the traffic, making it harder to trace and block the intrusion. This differs from phishing (which targets people), brute force (password guessing), or sniffing (passive traffic capture). Defenses include ingress filtering to block forged sources, and stronger authentication at higher layers such as TLS, IPsec, and multi-factor authentication.