Your Samsung Galaxy S4 certainly contains a lot of sensitive information such as important documents, banking information, password, email accounts and social networks, etc.. Can you imagine if this information falls into the wrong hands? In order to keep your information safe, you can enable the password mechanism of your S4 (lock screen):
Starting from the Home screen, open Settings> My Device > Lock Screen > Screen lock
Select "Password -High security"
Enter a password and confirm.
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