SHANGHAI - The rise of Android, one of the major operating systems for smart phones, has invited attacks by various malicious applications, giving rise to concerns among Chinese consumers and businesses alike.

These malicious applications have infiltrated Android and most often cause mobile phone users to unknowingly lose their phone credits or being slapped with an astronomical bill at the end of the month. Android is an open source system by Google Inc.

Experts said certain unscrupulous service providers are implanting malicious software into their popular applications in order to secretly charge users, without the knowledge of phone operators such as China Mobile or China Unicom.

To entice users, phone operators usually offer free downloads as part of their sales and marketing effort to boost profits. Proceeds from the use of applications are divided between phone operators and application service providers.

Xu Weite, vice-president of Gfan.com, a popular online community for Android users, told Sina.com that one in 10 applications for the Android system are implanted with malware. "The figure is set to rise as more and more low-end smart phones adopt the system," he said.

According to an October report by Analysys International, an IT consultancy company, the number of Android users in China has reached 8.6 million as of September 2010, and was on track to reach 10 million by the end of last year.

The Sina report says that there are at least 10 service providers in China that specialize in developing and disseminating malicious applications under the Android system. Complaints filed by users regarding irregular charges are on the rise among China's Android online communities.

A Web user named Xing recently posted his phone bill on Gfan.com, to share his grievance and to alert other users.

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His posting showed that a free application called "Tower Master" charged him 20 times more for a single usage that costs 2 yuan (30 cents). He claimed that he was not notified of the hefty charges.

Another user nicknamed Topk said he was charged more than 70 yuan in a month without official notification after he downloaded many "free" applications online.

"While opening up its source code has triggered the widespread application of the Android system, it has also made the system difficult to regulate and vulnerable to malware and viruses," said Fu Liang, an independent telecommunications industry analyst.

"Not only can malware and viruses ring up huge costs for consumers , they can also steal information. That poses a bigger threat as the mobile phones of today have become a place for consumers to store private information," he said.

A report this week from Lookout Mobile Security, a US-based provider of antivirus software for mobile devices, said a new virus dubbed "Geinimi" is affecting Android devices and it "can compromise a significant amount of personal data on a user's phone and send it to remote servers".