My friend started receiving frequent security notifications from WhatsApp, up to seven times a day : "Your security code with [contact] changed. Click to learn more."
When I click I read "because there was a login on a new device of theirs", or "because there was a logout from one of their devices".
She did not make any setting change to cause this. She did not change her phone. She has 2FA enabled, and has set her privacy to contacts only.
She had always been using WhatsApp web in her office and home, logging in and logging out. She did not receive such security notifications before.
According to the WhatsApp official help page : https://faq.whatsapp.com/general/security-and-privacy/security-code-change-notification/ : "At times, the security codes used in end-to-end encryption might change. This can happen because you or your contact reinstalled WhatsApp or changed phones." However, none of us reinstalled WhatsApp or changed phones. Some sources on the Internet commented that somebody is trying to hack into her phone.
Why is the attacker so persistent? What are they trying to achieve? Could they succeed with this brute force attack? Can something be done to punish the attacker?
Since the security notifications are annoying, she has turned off the security notifications, but her contacts like myself would still continue to receive these security notifications.