Ingress filtering is a technique used to ensure that incoming packets are actually from the networks that they claim to originate from. This is particularly useful in mitigating IP spoofing, where an attacker might use a legitimate IP address to send malicious packets, making it appear as though the packets are coming from a trusted source. By implementing ingress filtering, networks can check that the source IP address of incoming packets is within a range that logically should be entering the network from that point. This helps in tracing back flooding attacks to their true source and is a recommended practice to protect against such attacks.
References: The concept of ingress filtering is covered in EC-Council's Certified SOC Analyst (CSA) training and is a recognized technique for protecting against flooding attacks. It is also mentioned in the context of security operations center (SOC) processes and is a part of the knowledge base required for SOC analysts12.