A Gmail address is a simple, seemingly harmless tool anyone who has access to the internet can own. By simply signing up for a Google account, you can get as many as you care for.

However, Gmail accounts are not entirely the simple, harmless tools that some of us believe them to be. If your Android smartphone is playing host to Gmail addresses that aren't yours, get rid of it right away. Wondering why? Well, here are three reasons.

1. It Could Allow Access to Your Device Data

A Gmail address is like a unique identifier for a Google account. Remember, your Google account is what gives you authenticated access to Google's numerous products and services. To help improve its services to you, Google ties data about your use of its services to your Google account.

While this on its own is nothing to worry about, things get complicated when your Android smartphone enters the equation. Once a Gmail account is logged in on your Android device, or even on Google's Chrome browser for mobile, all your activities could be tethered to that Google account.

So, if you're launching a calculator app, opening your banking app, or playing a music video, Google keeps track of those activities and saves them to your Google account. Google tracks everything you search on Google Search, and the websites you visit after that, and saves it to your account.

Google has no way of knowing whether a Gmail account logged into your device is yours or not. As a result, if a Google account is logged in on your device, it doesn't matter who owns it, all your smartphone activities can be viewed and accessed by any person that can access that account. So every app you're using and the website you're visiting could be all up for the taking.

On the surface, a stray Gmail account on your device seems like nothing to worry about. However, it could be a gaping security and privacy loophole. It doesn't matter if it's the Gmail account of a trusted friend. If that friend's account somehow gets hacked, the security and privacy of your Android data could be in jeopardy.

2. It Can Access Your Location History

Apart from your usage activities, one of the most invasive things that a Gmail address logged into your smartphone can reveal is your location history.

This is critical to your privacy and security but surprisingly easy to access as long as a malicious user has control of any Gmail address logged into your device. All they'd need to access everywhere you've visited (shops, airports, schools, etc.) is to access the Google Maps timeline of the Gmail account.

3. It Can Be Used to Remotely Wipe Your Device

One of the most useful things a Google account does for you as an Android phone owner is to give you the ability to remotely wipe your data off your phone in the event of theft. Using Google's Find My Device feature, you can not only locate your device, but you'll also be able to erase every data on that device remotely.

All you'll need to remotely access an Android smartphone to erase data is a Gmail account logged into that device—it doesn't matter whose it is.

Of course, we logged in a Gmail address we control into a test device as a secondary Google account, and we were able to remotely erase all the data on the device afterward. All it took was two minutes.

Only Use Your Google Account on Your Device

It doesn't matter for what reason, do not allow Gmail accounts that can be accessed by others to be logged in on your Android device.

Although it seems completely harmless, it is the easiest, most subtle way of compromising your privacy and security without even knowing it. If you have a stray Google account on your device, this might be a good time to take it down. It doesn't matter whether you trust whoever has access to it, whenever their security is compromised, yours could be as well.