In one sentence: Account takeover is when someone else gets into your online account and uses it as if they were you.
Why it matters: Some first signs: you cannot log in, you get a notice about a change you did not make, you see a sign-in from a device or place you do not know, or friends get messages you did not send. If you see these signs, act quickly and stay calm.
One thing to do: Open your email account’s security page and look at recent sign-ins. If one looks wrong, change the password and turn on 2-step verification.
Related terms: credential stuffing, SIM swapping, phishing
Learn more: How to Secure Your Email Account (It Unlocks Everything Else); SIM Swapping: What It Is and How to Protect Your Phone Number
Checked: 25 Oct 2026. Rules and prices change. If yours looks different, check the organization's own page.
