How to secure clients on one VPS server?

Question

Malware

One VPS server hosts several customer sites (personal account). Each client will be able to upload files to his site, the question is: if the client uploads any file with a virus (accidentally or intentionally), will other sites on the VPS server be affected (the sites are on different domains and folders)?

Answer 1

If anything from clients is executed on your server, you should be prepared that this "anything" uses an exploit with elevated rights to root and will screw up the entire server.
No, it is not solved by the rights to folders.
Exploits that break through virtualization also happen, but less often, of course.
It is worth localizing the problem: what exactly clients upload to the site and how it is used. Proceeding from this, already dance further.
For example, if it's exclusively multimedia/documents/archives - just exclude the possibility that they will be processed in some way on the server.
If these are full-fledged sites and clients upload arbitrary scripts - well, cut the handler's capabilities ... and divide the rights into folders, of course.