IDS
termsecurity
Stands for: Intrusion Detection System
A system that watches traffic or hosts and reports what looks like an attack - and, as an IPS, blocks it.
The whole design question is the one letter. Detection produces alerts somebody must read; prevention produces outages when it is wrong. Moving from one to the other converts every false positive from noise into an incident, which is why mature deployments stage it: monitor, then block for a pilot, then block generally, with a date on each step. The second constraint is encryption - a sensor that cannot read the traffic is reduced to metadata, which is why so much of this capability migrated to the endpoint.
Also known as: Intrusion Detection System, ips