Is a separate user of ISPmanager a guarantor of the protection of other sites?

Question

Malware

Today I received a notification from the hoster that the server is sending spam.
Naturally, I scanned the entire server with two antivirus programs built into ISPmanager (virusdi and revision).
Several threats were found on different users.
The site files contain an encrypted code that does something for the distribution.
But the question is, is a separate user for each site a guarantee that other sites will not be affected?
That is, look for vulnerabilities only in infected sites, or you will have to shovel the entire server.

Answer 1

If the rights to the site files are correct, then he will not be able to get write access to the files of another user.
But it won’t hurt to check the rest of the sites, especially since the built-in antivirus allows you to do this, it won’t be superfluous.