Almost everyone owns a smartphone. People have become very attached to their smartphones that they are rarely without them. They keep them within arm’s reach, sleep next to them, and even use them when in the bathroom. What most people don't realize is that smartphones are a snooper's best friend. The features that make smartphones smart are the same reasons why the modern day smartphone is a private citizen's worst privacy nightmare. Just think about the information you have on your smartphone: email addresses, phone numbers, calendar appointments, photos, videos, possibly saved passwords, and financial information. Furthermore, smartphones can be used to continually track your location to monitor your whereabouts.
In spite of this, we can take some measures to ensure that our smartphones remain secure. If your phone is not secure and it got lost or stolen, your personal information, including your photos, passwords, banking information, and emails could be used to steal your money, or worst — your identity.
A Windows Phone is secured by design. Some of its security features are enabled by default. But, there are still a number of things you can do to help keep your personal information and your Windows Phone secure. Here are a few you can try:

Assign a Password or PIN Code on Your Phone
Setting up a password on your phone's lock screen is possibly one of the basic security measures you can employ to prevent unauthorized access to your phone. It might be a pain to constantly type a PIN or password every time you want to use your phone, but losing your phone without the protection of a password could lead to a far greater headache.
To set up a password or a PIN on your phone, go to the App list, tap Settings, and then tap Lock screen. Turn on Password, and then enter your preferred password in the New password and Confirm password boxes. Tap Done to save your changes.

Set Up a PIN on Your SIM Card
Setting up a SIM card PIN will prevent other people from making unauthorized phone calls with your phone. To set up a PIN on your SIM card, tap the Windows icon on the Start screen. Tap Phone > More > Settings. Turn on SIM security, and then enter the PIN for your SIM by doing one of the following:
  • If you are setting up a PIN for your SIM for the first time, enter "1234" and then tap Enter. 1234 is the default PIN for most SIMs. If the default PIN did not work, contact your mobile carrier for the correct default PIN.
  • If you have already set up a PIN on your SIM card, even if it was on another phone, enter your PIN, and then tap Enter. You will then receive a message saying "SIM PIN enabled."
Set Up a Wallet PIN
A Wallet PIN is a numeric password that you can assign to your Wallet. When combined with the lock screen password, it can provide an extra layer of protection and prevent unauthorized purchases in the Windows Phone Store and unwanted NFC payments.
To set up a Wallet PIN, go to the App list, tap Wallet > More > Settings+PIN. Turn on Wallet PIN, then enter and confirm your PIN code, and then tap Done.
You can also check the Use Wallet PIN to protect music, app, and in-app purchases box if you want to require this PIN when purchasing in the Windows Phone Store.

Use the Find My Phone Service
Find My Phone is Windows Phone's own built-in version of Apple's Find My iPhone and Android's Android Device Manager. Find My Phone can ring and lock your phone, show its location on a map, or erase its information if it is stolen. You can even send a short message containing your contact information that will appear on your phone's lock screen in case someone found your lost phone. To know more, click here.

Set Up Kid's Corner
Kid's Corner is a safe place for your children to play with the games, apps, music, and videos added there, while restricting them from accessing your phone settings and making any changes. To set up Kid's Corner, go to the App list, tap Settings > kid's corner. Select the AppsGamesMusic, and Videos you want to add, and then tap Done.

Regularly Back Up Your Data
Make sure to back up your phone settings, photos, videos, text messages, and contacts to cloud. It’s a good thing Windows Phone has a feature that allows you to automatically back up your important phone settings and data to cloud in case something untoward happens to your phone.
To turn on apps and settings back up, go to the App list, tap Settings > Backup > Apps + settings. Turn on Settings backup and App backup. You can also back up your text and chat messages by turning on Text message backup and Chat backup.
To auto upload your photos and videos to cloud, go to App list, tap Settings > Backup > Photos + videos.

Keep Your Phone Updated
Like any device, your Windows Phone will work better when it is running the latest Windows software update as well as the manufacturer update, if there's any. That is why it is recommended to download and install any update available for you.
To automatically download updates, go to the App list, tap Settings > Phone update, and then check the Automatically download updates if my data settings allow it box.