Do you suspect they are spying on your WhatsApp? This is how hidden sessions are detected and closed
WhatsApp lets you identify unauthorized logins to your account so you can close them
To find out if a hacker has logged into your WhatsApp or if you have a "ghost session" open, the trick is to frequently check the "Linked Devices" section and close anything you don't recognize. WhatsApp displays each active session (mobile, PC, browser) and lets you close them immediately from your own phone.
Signs your WhatsApp might be hacked
If someone opened your WhatsApp on another device, you'll usually see small, strange changes to your account. They aren't always obvious, but there are several clues:
If something like this happens, the first thing to suspect is a session opened on another device or someone who had physical access to your phone and scanned the QR code without you noticing.
How to see and close phantom sessions on WhatsApp
WhatsApp has a key feature for detecting phantom sessions: "Linked devices," which shows all the places where your account is active (computers, browsers, other mobile phones, etc.). From there you can see the device type and last active time, and close everything with a couple of taps. Ideally, you should make this a routine security check, just like checking your email or notifications: a quick look at "Linked Devices" to ensure only your devices have access. That way, if a hacker left a phantom session on a shared PC or someone else's browser, you can kill it instantly. Extra steps to secure your WhatsApp account: In addition to hunting down phantom sessions, it's key to strengthen security so that no one can log back in, even if they have your number. WhatsApp integrates several layers that you should activate right now: By activating these protections and regularly checking your linked devices, you greatly reduce the chances of having a phantom session or an intruder reading your chats without you noticing. WhatsApp does let you see all active sessions and close them whenever you want, but it's up to you to log in every now and then, look at the list, and disconnect anything that doesn't seem familiar.

