The immune system
It logs into your servers with a login of its own and keeps watch. On a new machine it takes a baseline; after that it tells you what changed, with the evidence and the exact commands it would run, and nothing changes until you say so. It carries a blue-team playbook and never gets root or sudo.
- Uptime, load, memory and disks filling up
- New users, new SSH keys, failed logins
- Persistence: cron jobs, systemd units, ld.so.preload
- Reverse shells, tunnels and miners
- Web shells in upload folders
- Ports open that shouldn't be
- Lynis score and security updates, run to run
- TLS certificates about to expire