Anyone with an iPhone or Android should turn their device on and off once a week, officials say - to protect them from hackers.

The idea is to thwart 'zero-click' hacks, which involve downloading spyware onto users' phones without them ever clicking a link.

The National Security Agency (NSA) endorses the rebooting method, which temporarily deletes the massive stores of information that continuously run in the background - such as on our apps or internet browser.

The NSA has also warned that users should be wary about connecting to public WiFi networks and are advised to update their phone's software and apps regularly.

An NSA document listed the many steps all iPhone and Android users should take to mitigate the risk of a cyberattack.

Restarting your phone is one of the lesser-known methods.

Unlike other forms of malware, zero-click attacks don't require any interaction from the victim. 

Hackers prey on a software vulnerability and gain access to devices, without having to dupe you into clicking a malicious link or downloading a malicious file.

If the system isn't turned off and on, a cybercriminal can manipulate opened URLs to run code that installs malicious files onto the devices.

By turning the phone off and back on, it forces the closure of all apps and logs out of all bank and social media accounts, therefore preventing the hackers from accessing sensitive information.

The reboot method also has the same effect on spear-phishing attacks - when an attacker sends targeted fraudulent emails to steal sensitive information like login credentials.

Nearly half of smartphone owners reported they rarely or never turned their cell phone off, according to a 2015 Pew Research study, while 82 percent said they never or rarely rebooted their phone.