Malware on Google Android devices is becoming more and more of a problem for smartphone owners. Until now, malicious apps such as DroidDream and DroidDream Light, had exploited bugs in earlier versions of the OS but wouldn't affect those devices running Gingerbread (version 2.3). However, now researchers have spotted malware that exploits a critical vulnerability in this version of Google's mobile platform.

The safest course of action is to avoid apps that you've never heard of and to research apps and their publishers thoroughly before pressing the Download button. When you install an app, you'll see a list of permissions for services that the app can access on your device. But an alarm clock app, say, probably shouldn't need to access your contacts. If something in the permissions screen looks fishy, just don't download the app.

However, if you are concerned about the software already installed on your Android smartphone, then there are a number of free security apps available in the Android Market that will scan your phone and identify any rogue apps. Here's five of the best.

Lookout Security & Antivirus

Not only will this app scan your handset for malware, spyware and Trojans, it will also check every app before you install it in the future to ensure its not malicious. It even lets you back-up your contacts and data stored on the phone and locate if your handset is lost or stolen.

AVG Anti-Virus Free

Just like its free desktop software, AVG Anti-Virus for Android smartphones will protect you from viruses, malware and exploits in real-time. With the app users can scan content stored on their handset as well as locate their handset if lost and even back-up their data.

Bitdefender Mobile Security

Like other Android security apps, Bitdefender Mobile security will scan your handset for malware and let you locate your smartphone if lost or stolen. However, this app also lets you see what applications have been granted permission to access your private data, connect to the web or even send text messages.

Norton Mobile Security Lite

This app detects and removes mobile security threats used by cyber-criminals to steal your personal info, spam you with texts, or take control of your phone.

Webroot Mobile Security Basic

This free app from Webroot blocks and removes malicious apps, as well as blocking phishing and other malicious websites and even stops unwanted calls and texts.