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The Tetragon Way: From Observe to Enforce with bpf_send_signal

Tetragon is the Cilium ecosystem's runtime security tool: it observes with kprobe/tracepoint (the very hooks Part II used) and then enforces inside the kernel. Its enforcement uses two helpers — bpf_send_signal sends SIGKILL to kill a process, and bpf_override_return overrides a syscall's return value. This article rebuilds that: an exec tracepoint calls bpf_send_signal(SIGKILL) the moment a process runs — a forbidden binary gets exit 137, a normal binary still runs. No LSM, no reboot.