Additional security tests

[S-Coyle]

Specifically thinking about additional security checks to ensure we are locking down Electron as we should be.

There is what seems to be a useful Electron checklist of security recommendations here.
It seems we should verify that we are following these recommendations, and where applicable, add tests to confirm that these recommendations are effective and do not regress.

Other specific acceptance criteria that we must test to ensure we meet:

1. Nothing is written to the file system when no write permissions have been granted.
2. Ensure no network requests are sent out when not authorised.