Google’s Android operating system is like a house with open doors. Unlike Apple's iOS platform, Android allows anyone to develop and distribute an app – even without going through the official Google Play Store. 

What is a boon for independent programmers can be dangerous for users, since apps containing spyware or malware can be inadvertently installed on the phone. Antivirus apps are available, but are they any good? 

A study of the main antivirus apps for Android by the independent IT security firm AV-Test found that they nearly all achieved good protection. Only two apps failed the virus test: Lookout Antivirus & Security and AVG AntiVirus Free spotted significantly fewer threats than their competitors. 

The test found that free apps protected just as well as paid ones. 

"Which protection app you choose depends more on the additional features or the price," said Andreas Marx of AV-Test, which is based in Germany. The more expensive apps offer additional features such as the secure deletion of data or a function to find a lost smartphone. 

That the test found very similar performance when it comes to protection is because the antivirus apps all operate in the same way: by comparing the apps on the phone to a database of potentially harmful apps. 

The more up to date the database is, the better the protection. 

"We are currently aware of around 10 million malicious apps," Marx said. In comparison to the approximately 500 million viruses that can infect Windows computers, that number is still relatively small. 

Criminals are particularly interested in personal data – they earn their money using stolen accounts and passwords. 

Spy software hidden in apps is one way to get that information. Particularly dangerous in this regard are those apps that aren’t downloaded via the Play Store, but from elsewhere. 

One way to protect yourself from malicious apps, says Carsten Cordes from an institute for internet security in Germany, is to stick to trusted sources: "Viruses and malware hide in Android in harmful apps. As long as one avoids them and only installs apps from trusted sources there’s no risk." 

On Android phones you can set the security settings so that apps from unknown sources are not installed. It can still happen, however, that malicious apps get through the security checks at the big app stores. 

As Google checks the apps on its Play Store, it’s debatable whether antivirus apps are necessary, provided one sticks to downloading from the store. "Each of these apps claims for itself privileges on the device such as access to data, photos and contacts," says Cordes. 

"That’s something that every user ought to review for their individual circumstances." 

Other tips for safer use of Android devices and smartphones in general include being careful in public WiFi hotspots, having WiFi switched off then travelling and carrying out online banking only when at home behind an effective firewall. 

In addition, updates should be installed promptly, because they often plug security holes. — dpa