To increase the security of your accounts it is advisable to use Two-factor Authentication.
Google’s version is called 2 Step Verification.
By using 2FA you are supplying two pieces of information to authenticate who you are. You are verifying your identity.
A common example is when I attempt to log into an account, a code will be sent to my phone which I have to type into the web-page before I can continue. So even if a hacker knows my password, they would need to have my phone before they could access my online account. There are variations on this which I won’t go into, but for anyone not using 2FA who is unfamiliar with it, just search Google using (I will use Facebook as an example) “2fa facebook” (without quotes) and you can find out how to set it up.
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