Even though Android, the software developed by Google and running on just one phone sold by T-Mobile, is open source, it is unlikely to be more susceptible to malware than other, proprietary mobile operating systems, said Charlie Miller, principal analyst at Independent Security Evaluators and the researcher who found the first Android vulnerability.

While a developer could write a harmful application and distribute it via the Android Market, Google has put up some roadblocks that would make it hard for malware to cause much harm, Miller said. "If you want to do anything dangerous like access personal contacts, you have to specifically say to the virtual machine 'these are things I'm going to have to do,' and the virtual machine will ask the user if that's OK," he said. Android applications run in a Java virtual machine on the phone.

For example, if a user downloads a Scrabble game containing malicious code that tries to gather information from a user's e-mail account, the phone will ask the user to approve the application's access to the e-mail account. In that case, the user would decline the download, realizing that a Scrabble game shouldn't need to read from an e-mail account, he said.

Just this week, however, hackers discovered a way to install applications natively on the phone instead of using the virtual machine. The capability could open doors to new security threats by letting applications access any phone function. Google said it has developed a fix for the bug and plans to push it out to users soon.

That is the second vulnerability to be discovered in as many weeks. The first, discovered by Miller, resulted from Google using outdated open-source code that didn't include an update already issued that closed the hole. But such vulnerabilities aren't unique to Android or open-source software. "The fact is, you could do that against the iPhone or against the BlackBerry or whatever. All these phones have issues," he said.