This is great defense in depth but if someone gets RCE on your host then I would assume that entire box is compromised. Local privilege escalation is very frequently possible, only costs ~$50k for a 0day [1] and there are tons of free PoCs available if you don't keep your systems fully patched.

The protection I would highly recommend everyone use is enabling Amazon's "v2" metadata service [2] in enforce mode, which will neuter nearly all SSRF metadata attacks. This won't do anything if someone has RCE on your host, but it would have prevented the Capital One breach the author uses as their example. Nearly every metadata compromise in recent history has been through SSRF.

Another aspirational read is how Netflix detects credential compromise [3]: the first time a host asks for metadata credentials they save its ip address, and if they ever see those credentials used from a different ip address they alert on it.

[1]: https://zerodium.com/program.html

[2]: https://aws.amazon.com/blogs/security/defense-in-depth-open-...

[3]: https://netflixtechblog.com/netflix-cloud-security-detecting...