This is common knowledge; you should use a combination of alphabets, numerical digits, and special characters (!, @) to create strong passwords. Yet, the most commonly used password on the Internet is 123456 followed by 12345 – see full list.
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… Microsoft too offers an online tool that will instantly tell if your password is strong or weak.
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Enter Password Meter – this is an online tool that will not only rate your password’s strength but will offer clues on what you kind of characters can you add or remove to improve the password’s strength.
Source : Digital Inspiration Technology Blog
