Samsung
Lock Secure Folder Manually auf Samsung
Secure Folder on Samsung phones does lock itself automatically, but only once a condition you set beforehand is met. Depending on that setting, the folder stays accessible until a timer expires or you restart the device, not the moment you actually leave it.
That delay matters if someone else picks up your phone right after you close Secure Folder. The content inside stays reachable for as long as the automatic condition is still pending, even though the folder looks closed on screen.
Close it on the spot
Secure Folder has its own menu with a direct lock command, independent of your timer setting. Go to Tap on Secure Folder ➔ Open the Menu ➔ Tap on Lock and exit. This closes the folder immediately and requires the usual PIN, pattern, or biometric check the next time you open it.
Use this whenever you hand the phone to someone else or step away in public, even briefly. Keep the automatic timer active as a backup for the times you forget the manual step, since both methods work independently of each other.