Source-address validation is a network control that checks whether an incoming packet really appears to come from the source address it claims. In practice, routers, firewalls, and upstream providers compare the packet’s path and interface against expected addressing rules and drop traffic that looks spoofed. This is especially important because forged source addresses are a common trick in scanning, reflection attacks, and stealthy botnet traffic.
For defenders, source-address validation reduces abuse of trust in network packets and makes attribution harder for attackers to fake. It is often discussed alongside anti-spoofing controls such as ingress filtering and reverse path checks. In botnet environments, it helps prevent compromised devices from sending packets that pretend to originate elsewhere, and it can limit evasive traffic that tries to blend into ordinary UDP flows. It is not a complete defense by itself, but it is a strong baseline that makes protocol camouflage and reflection-based attacks much less effective.