Bouncer is a service that Google has been working on for some time. Just announced on Thursday, Bouncer scans the Android Market for potentially malicious software automatically. With Bouncer, Google can protect users against malware while still removing the (some call draconian) application approval process of the App Store from the equation.
To detect malicious software, Google looks for known signatures as any antivirus might do, but also runs apps on a simulator in the cloud. The company also analyzes new developer accounts to help prevent repeat-offenders from returning.
What's interesting, though, is that Google said that Bouncer has been running silently, sans publicity, for some time. The company was vague, and said "for some time," but they also indicated that from their estimates, Android malware is declining.
The news was met with approval, but also criticism, as some had been calling for Google --- if it wasn't going to curate apps --- to scan them, instead, since the Android Market opened.
said "We think it is great that Google is working with the Android community to provide an alternative to a manual curation process, allowing developers to innovate quickly while also increasing the baseline level of security for Android users."
We have security software on all our Android devices, but not as much for protection against malware as for protection against loss or stolen devices. The software we use allows remote lock, location, and remote wipe, to protect against instances when our devices --- with all our important data --- might be lost.