denial of service
an attack that knocks a service offline rather than stealing from it
A denial-of-service attack stops people using a system. It might crash the software with a malformed request, or swamp it with traffic. Nothing need be stolen, but staff cannot log in, customers cannot reach the website, and the business stops until the service recovers.
Think of it as
Jamming the shop's front door with a broken lock so no customer can get in.