Integrity monitoring is a very common practice on server security, generally done inside a file system, where it creates a cryptographic checksum of all your files and if something changes you get an alert. Useful, no? This is called FIM (file integrity monitoring).
What we don’t see often is this kind of integrity checking being done to your Internet assets. What if someone modifies your site in the middle of the night? Or changes the registration information of your domain? When will you find it out?