Who do these AWS credentials belong to?

Let's say you've found an AWS_ACCESS_KEY_ID and an AWS_SECRET_ACCESS_KEY, whether that's on your local machine's ~/.aws/credentials, in your project's environment variables, etc - the important next question is "are these still active, and if so what access do they have?".

Fortunately you can use aws sts get-caller-identity to do this, for instance:

env AWS_ACCESS_KEY_ID='XN...' AWS_SECRET_ACCESS_KEY='fpQ...' aws sts get-caller-identity

This then outputs, for instance::

{
    "UserId": "...",
    "Account": "...",
    "Arn": "arn:aws:iam::...:user/..."
}

Or if the keys are no longer value, you'll get something along the lines of:

An error occurred (InvalidClientTokenId) when calling the GetCallerIdentity operation: The security token included in the request is invalid.