Security experts warn billions of iPhone users to turn off three settings that are on by default

Security experts have issued a stark warning to billions of iPhone users to turn off three settings that will be on by default.

National security officials have warned Apple device users that they automatically have three settings enabled at all times, which could be exposing their vulnerable data to cybercriminals.

Hackers could get their hands on your social security number, credit card details, passwords, personal photos and even your home address - some key ingredients for cyberpunks to drain your bank accounts, steal your identity or sell it on for a profit.

Cybercriminals could disguise their malicious hotspots as free Wi-Fi in public places (Getty Images)

The Wi-Fi and Bluetooth setting

The first setting to be mindful of is Wi-Fi as, while leaving it to search for available networks when you're out and about sounds convenient and data-friendly, it could automatically connect to a dodgy hotspot controlled by a hacker.

The hacker can then harvest your data, even after you've disconnect, and instal malware onto your phone.

That's because having the WiFi setting turned on leaves your device constantly searching for available networks - and when it finds one, it automatically connects, even if you didn't ask it to.

They are most commonly around in public spaces where Wi-Fi tends to be freely available, like coffee shops, bars and restaurants.

The National Security Agency (NSA) says tricksters could be hiding by changing the Wi-Fi name to that of a nearby hotel or restaurant, and call this type of attack an 'evil twin' for them going disguised as a regular Wi-Fi network.

Hackers can gain access to your device over Wi-Fi or Bluetooth (Jaap Arriens/NurPhoto via Getty Images)

Cyber security company Kaspersky says such attacks are 'the biggest threat to free Wi-Fi security,' as hackers can 'position [themselves] between you and the connection point.' They continued: "So instead of talking directly with the hotspot, you’re sending your information to the hacker, who then relays it on."

To protect your device, you'll need to disable the automatic Wi-Fi setting by turning off the option for 'Auto-Join Hotspot'.

The NSA also advises iPhone users to be mindful of connecting to public Wi-Fi networks that don't require a password to gain access, as they are 'vulnerable to theft or manipulation.'

Likewise, leaving Bluetooth searching can not only drain your battery but expose you to a 'BlueBorne' attack, and can be similarly toggled off.

Location services

Another major red flag comes under the iPhone location services.

You might be familiar with the pop-up when using a location-based app that asks you if you'd like to turn the location tracking on 'at any time' or just when using the app.

However, tech gurus warn permitting apps to access your location all the time could present hackers with a goldmine of information if they're able to get their hands on it.

Tech pros warn having location turned on could be putting you at risk (Getty Images)

Take for instance one situation in January when hackers were able to compromise the app Gravy Analytics, which collates data from users to help businesses engage with their customers.

However, hackers grabbed tonnes of data, including information that mapped users' exact movements.

You can turn the setting off easily enough by going to settings, privacy and security and tapping location services.

In location services, you can see all the apps you're sharing your location with and tap them off.

Specific Apple apps, like Maps and Weather, require your location to help you travel and pinpoint where you are, but you can limit how much they track by tapping this to the option that only looks at your location 'while using' the app.

App tracker

Have you ever been convinced your phone is 'listening' to you? Perhaps you were talking about an item and then all of a sudden, boom, you're hit with adverts about it.

Some apps may be sharing your personal data without your knowledge (Getty Images)

Well, that's because your phone is constantly collecting data about you, and your apps communicate this data when building your digital profile, from your device ID to your name and email address and other user behavior info.

Fortunately, you can put a stop to this too by using 'App Track Transparency' that is already built into your device.

The app allows you to see which apps are tracking you and what data they're collecting about you.

Under the privacy and security section in settings, click tracking.

If the 'allow apps to request to track' is toggled on, then your apps could be tracking your usage which again could be a treasure trove if fallen into the wrong hands.