system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Where do viruses go when they are quarantined, but not deleted?

How are they kept in the computer without further damaging the machine or running?
gpt
Most anti-viruses do it very similarly. Here's what Symantec/Norton anti-virus does:

1. Load the malicious file into memory.
2. Encrypt it with a simple algorithm. (Something similar to subtracting 10 from every byte. So if the virus's code looked like KLM, the encrypted version would become ABC.)
3. Move the encrypted version to some folder like C:\Symantec\Quarantine.
4. Delete the original file.

The encrypted version is basically rendered inert; it's as if it's been deleted. The bytes in the file are completely different and cannot be run, opened, viewed, etc. If you open Symantec and view the quarantine folder, you can choose to restore it, which just means decrypting it and moving it back to its original location.

This is also why ransomware malware is effective. By encrypting every file on your computer and throwing away the key (retaining a copy for themselves, privately), they've effectively made everything inert, as if they deleted all your files. By paying money, they can send the key back to you.