Millions of Android users are being warned to check their phone for a string of apps which have been hijacked my malicious viruses.

There are three main viruses currently using 19 apps to steal sensitive information and secretly sign up users to premium services, monetising the infection.

One of the malware strains has already been downloaded more than three million times.

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Because Android is an open source operating system, it can run any third-party app, unlike iOS.

While this makes devices more customisable, it also leaves them open to harmful cyber attacks, with malware commonly hidden in the coding of seemingly harmless apps.

According to the experts at MalwareFox, cyber criminals download real apps from the Google Play Store, and inject malicious viruses into the backend coding of those programs, before re-uploading them to the store under a new name.

Malware is always adapting and finding new ways to invade devices, but cybersecurity experts are always on the hunt for them.

Here are the viruses currently doing the rounds, and the apps they are hiding in, according to MalwareFox.

Joker Spyware

This spyware gathers sensitive data like contact lists and SMS messages, and can register the device for premium services without consent.

It is hiding in the following apps:

• Simple Note Scanner – com.wuwan.pdfscan
• Universal PDF Scanner – com.unpdf.scan.read.docscanuniver
• Private Messenger – com.recollect.linkus
• Premium SMS – com.premium.put.trustsms
• Blood Pressure Checker – com.bloodpressurechecker.tangjiang
• Cool Keyboard – com.colate.gthemekeyboard
• Paint Art
• Color Message.

Harly Trojan

This Trojan uses China Telecom’s code — 46011, according to Malware experts at Kaspersky, which say it gives clues to suggest the malware developers are located in China.

It can also subscribe users to premium services in an invisible window to monetise the infection.

It is hiding in the following apps:

• Fare Gamehub and Box
• Hope Camera-Picture Record
• Same Launcher and Live Wallpaper
• Amazing Wallpaper
• Cool Emoji Editor and Sticker

Autolycos Malware

This malware has already been downloaded more than three million times, according to PCrisk.

It also…