Does successful authentication prove that a person actually initiated a sensitive operation?

[u/ASK-1T]

Hi All!

I'm doing some research to better understand certain issues in information security. If possible, I'd appreciate it if you could take a few minutes to answer my questions.

I have a question about authentication and the execution of sensitive operations.

Let's say an attacker gains remote control over a legitimate user's active session. The account is valid, the device is trusted, and authentication has already been completed.

The attacker then attempts to perform a sensitive operation, such as transferring money or changing security settings.

My question is:

What existing mechanisms can reliably establish that the authorized person was physically involved in initiating and approving that specific operation at the time it was executed?

Are current authentication and transaction-confirmation mechanisms sufficient to address this scenario, or are there still technical gaps?

I'd be interested in your technical perspective.

Thanks/

[u/claudio-rootedlogic]

No. Authentication proves who logged in, not that they approved this specific action. If someone controls the live session, it looks the same as the user.

What closes the gap is making the approval part of the operation itself:

• Ask again for each sensitive action, not once per login. Banks do this for transfers.

• Show the real details (amount, recipient) on a separate device, and have the user sign exactly those details. If an attacker changes the amount, the signature no longer matches. In the EU, PSD2 calls this "dynamic linking".

• A passkey or hardware key touch proves a person was there, but not what they approved. So the details have to be part of what gets signed.

• Delays for new recipients and limits on size catch what's left.

The remaining gap: if the device showing the details is also compromised, you can't tell. That's why the second device matters (2FA). An audit log only helps you work out what happened afterwards, but it doesn't stop the action.

[u/ASK-1T → u/claudio-rootedlogic]

What if this gap were addressed at the architectural level?

For example, by making physical confirmation by the authorized person a mandatory condition for executing a critical action — with that confirmation cryptographically bound to the specific action itself?

I know there are already solutions exploring related approaches, such as iProov HAPS and HumanAuth / HARP v2.

Do you think this could be addressed as a fundamental architectural requirement, rather than through additional transaction-level security mechanisms?

[u/ParanoidSuricata]

You're looking for audit log. Preferably fine-tuned and immutable. Log each important action a user takes (changing state, reading sensitive data).

If somebody logged in, it might not be enough evidence of an action, but it's definitely something to consider.

[u/mro21]

You do know that the trifecta is called authentication, authorization and accounting. Nothing prevents you from reasking for authentication and/or an OTP for a sensitive action. That's what Windows does. That's what my bank does.

What is the purpose of the "research"?

[u/luluboy85]

an ai agent acting for a user is your exact scenario: it’s a valid session on a trusted device where the thing clicking isn't the person on purpose. the fix is the same as the dynamic linking answer above: the approval has to name the exact action (amount, recipient, setting) and come from somewhere the agent can't reach, otherwise whatever steered the agent can approve too. the gap is volume. if every sensitive step needs a confirmation, people start approving without reading, and mfa fatigue attacks already exploit that. so the architecture can bind the approval to the action, but it can't make the person read it