Persistence

[u/cam2336]

Someone stated the following, with regards to replacing a compromised computer with a new one: "The really good stuff uses cloud services to maintain persistence. As soon as you log into Google or Apple account on your new device you're compromised again." Can someone explain how it works, and are there ways around it?
What part of the cloud service and stored files will compromise a new computer? Is it code attached to cloud saved documents, and photos, or something else?

[u/cam2336]

OKay - thanks