Rootkit has another connotation. The kit installs itself in a way that it has root (or admin) access to the full system resources. Usually it uses that to hide itself. They don’t always provide any remote access to the system either.
The whole purpose of the old sony rootkit was to prevent folks from ripping cds to the hard drive. It didn’t allow remote control or snooping, it just fscked up cd access. And it hid itself so it was a major pain to remove.
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