The malware scanner which comes with Google's latest Android 4.2 Jelly Bean operating system has a detection rate that falls far behind that of third-party anti-virus products, a new study has shown.

Researchers at North Carolina State University who looked at the updated OS for smartphones and tablets said the service needs much improvement before it's considered effective.

The study, titled "An Evaluation of the Application Verification Service in Android 4.2 Antivirus", said anti-virus software needs to have a malware detection rate of more than 80 percent to be considered effective. However, out of more than 1,200 malware samples tested, the Android scanner detected only 193 - a detection rate of only 15.32 percent, the study found.

"By introducing this new app verification service in Android 4.2, Google has shown its commitment to continuously improve security on Android," said Xuxian Jiang, Associate Professor in Department of Computer Science at NC State University, who led the study. "However, based on our evaluation results, we feel this service is still nascent and there exists room for improvement."

The in-built Android scanner checks apps downloaded from marketplaces other than Google Play - the official Android app store. The study says that the weakness of the scanner is the limited amount of data the service collects on an app in order to see if it matches malware traits. This data includes the app name, size and version, the URL associated with the app and the SHA1 value - a cryptographic hash function designed by the National Security Agency.

These mechanisms can easily be bypassed by cybercriminals and to make the service more effective Google would need to gather more information, such as uploading the whole app to its server for analysis, Jiang said.

But this would cause unacceptable delays for many Android users as well as raise privacy concerns.

"It really requires a very delicate tradeoff," said Jiang, who suggested Google was erring on the side of caution in gathering user data.

"So far, too little information has been used," he added. "Google has been very cautious in trying to avoid triggering user concerns on privacy."

Most Android users can avoid running into malware simply by only downloading software from Google Play, where each app is vetted by Google before it is made available.

"If the user just buys the phone and never uses any additional apps and never clicks any untrusted links, then likely he will not need any [antivirus] solutions," Jiang said.