Lockheed Martin's 7-phase intrusion model. 28 representative techniques across the chain, each cross-linked to MITRE ATT&CK where applicable.
Pairs naturally with the Diamond Model: the kill chain answers where in the intrusion timeline; the diamond answers who and against what.
The attacker harvests information about the target - people, technology, infrastructure, partner networks, certificates, exposed services. Most of this is passive (OSINT) and indistinguishable from legitimate research.
Attacker goal
Build a profile rich enough to pick the right initial-access vector.
Defender goal
Reduce attack surface and detect targeted scanning that crosses into active recon.