Smartphones have become ubiquitous on urban streets and subways throughout China, though the sight of a tech-savvy young commuter pulling out their phone and shaking it to find nearby contacts can seem strange to the uninitiated.

New applications allow users to track or find new contacts, with an array of unusual techniques at their disposal - functions such as "message in a bottle" allow users to send a message out into the world, which may or may not wash up on a stranger's phone.

Applications of these types crop up almost on a daily basis, in a manner that was unheard of just a few years ago. But as these new applications become popular, few have realized the dangers that they potentially pose for unwary users.

Old crimes, new methods

Apps including Weixin, Momo and Jack'd, which can be used with Apple's iOs or Google's Android operating systems, have burst onto the scene and quickly become popular among Chinese youth.

While they've attracted the attention of a solid customer base, they have also drawn the attention of criminals who have devised ways to use the applications for their own ends.

Whether it's for theft or sex crimes, applications that allow users to instantly pinpoint and contact potential victims anonymously have already made crime easier for perpetrators.

According to reports in Xinhua, A local court in Zhejiang Province sentenced a 32-year-old man surnamed Cao to eight years and six months in jail for raping women he accosted via Weixin, a social networking app that has garnered over 100 million users since it was developed by Tencent, a Shenzhen-based company, at the beginning of last year.

Cao introduced himself to young women in colleges surrounding the city of Ningbo via a function called "look around," which allows users to see other users who are nearby. After gaining their trust, he then drove the women to a remote place and sexually assaulted them. Cao admitted to the police that he raped seven young women.

Police in Hangzhou, the capital city of Zhejiang Province, told the Global Times that since December last year, they had received some 20 Weixin-related theft and fraud cases.

Jack'd, a social networking app for gay singles that utilizes GPS has also cropped up in a number of crime cases, with booty calls providing more than one kind of booty.

"I got in touch with someone in March through Jack'd, and after chatting for a week we had a one-night stand. But when I woke up the next morning, the guy was gone, along with my iPhone 4S, a Louis Vuitton wallet and even my 3,000 yuan jeans," a gay man in Beijing, who preferred to remain unnamed, told the Global Times.

"I drank a glass of water, which he'd put a sedative in while I was in the shower. The guy vanished after that night, and the police haven't found him," he added.

The apps also have other unintended problems. Another Jack'd user surnamed Zhang told the Global Times that he was often bothered with spam messages. "Male prostitutes and masseurs always text me on Jack'd with nude photos and 500 yuan packages that cover any kind of service you can imagine."

Pointing the finger

With crimes relating to apps on the rise, it's no surprise that fingers are being pointed. In the case of Weixin, the most obvious direction to point them is in Tencent's direction.

According to an online poll conducted by news portal ifeng.com, by Tuesday, some 42 percent, or 13,361 of the total 31,742 respondents, said Tencent should accept part of the responsibility for crimes by Weixin users.

"Although there are privacy settings in Weixin, this is not enough," Chen Qifeng, an office worker in Shanghai, told the Global Times, adding that "as more functions are added, the difficulty of assuring user privacy also increases."

"Personally, I think Tencent should keep a record of key information such as mobile phone numbers, as most users open their account via their phone," a police officer surnamed Chen from the Hangzhou Public Security Bureau, told the Global Times.

Xia Jiapin, a lawyer from Zhejiang Brighteous Law Firm, said that the developer also has an obligation to notify users of the potential danger that some functions may involve.

However, Tencent is strengthening safety measures too. When mentioning Chinese words such as "bank card" and "bank account" in Weixin text messages, an alert will be shown to inform the user of the possible consequences.

"Real-name registration is also one possibility, if necessary," said Chen, a police officer from Hangzhou. "What we can do now is establish a safety net around users."

Questions from the Global Times regarding Tencent's plans for updates or safety measures went unanswered as of late Sunday.

However, another 15,700 people, representing 49 percent of those surveyed, were of the opinion that the company bears no responsibility for these crimes, reasoning that gunmakers can't be blamed for crimes committed with their guns.

Some 2,683 surveyed also suggested follow-up laws are needed.

Staying safe?

"Sometimes, we find it really hard to find laws that define crimes relating to cellphone-embedded social-networking applications," an official from the Xicheng District People's Procuratorate, surnamed Zhou, told the Global Times.

"Updating the law is imperative, but it needs time, and it's quite possible that once a new law on such rapidly developing technology is finally introduced, its terms are too obsolete to be followed," said Zhou, adding that if terms are written vaguely and generally to guard against becoming outdated, police hands will be tied when handling cases.

Police in several Chinese cities have also given warnings to the ever growing numbers of cellphone social networking app users.

Police in Guangzhou, Guangdong Province, took the initiative with a public notice in April that said that the city has seen a series of robberies and thefts from credulous Weixin users, and asked young women to be more cautious when receiving messages from strangers.

Beijing and Nanjing police authorities also sent similars alerts to Weixin users with some tips about how to handle these situations if they do occur.

"For us users, I think self-respect and a healthy attitude toward these showy apps is the best defense," Chen Qifeng said.