When root meets immutable: OpenBSD chflags vs. log tampering

ISO 27001 is like that careful lawyer who never says exactly what they mean – it tells you what needs to be achieved, not how to do it. When it comes to logging, this is particularly telling: Control A.12.4.2 simply states that “logging information and logging facilities shall be protected against tampering and unauthorized access.” Period. How? That’s your problem to solve.
↫ Rafael Sadowski

It turns out OpenBSD has a few relatively simple tools to make logs immutable, in a way that not even root can delete or modify them, or change any of the logging schedules. Reading through the blog post, you don’t even need a ton of intricate knowledge to set this up, thanks mostly to just how much innate sense OpenBSD tends to make, and how excellent the documentation is.

I have no need for this level of security, but if you do, you can set this up in a few minutes.