Google’s open approach to things is a double-edged sword when it comes to apps. On one hand, there isn’t a huge barrier to entry to try and make a app and make it available to the marketplace but on the other hand the lack of policing or app review makes it extremely easy to slip malicious code through the store to wreak havoc on individual users. Google hasn’t been sleeping though, and have created a service named bouncer that takes care of the malicious apps that try to get into club Android. Though only detailed a few days ago, the service has already been in place for quite some time now, which basically scans and analyzes apps being submitted to the marketplace and runs it against a background check of known virus signatures and behaviors. Since the appearance of the service in the first and second half of 2011, Google says that there’s been a 40% drop in the number of potentially dangerous downloads from the Android market.
This doesn’t mean you should download everything in sight however. Android users should always be wary of potentially malicious apps in the marketplace, and should always use a hefty does of common sense when downloading anything.
Source: Google Mobile Blog