According to a blog post on Symantec website on July 23rd, the fake app, which was released at the GooglePlay and supposed to function by extending your smartphone's battery life by twice as much as usual, was actually designed solely to steal your contact lists from your phone. They were so shrewd in tricking smartphone users and the trick the used was so simple.
The name of this fake app was "Denchi Nagamochi", literally means for longer battery life. They used the catchphrase "To run your smartphone for twice as long" to lure users. Most users are constantly suffering short battery life on their smartphone, so no wonder it attracted so many victims.
Once you install the app and open it, the setting screen is displayed as seen below. But this screen is displayed only for a second and right away displays another screen saying "Your device is not compatible to this app", and you can't do anything with it. But it is actually stealing your contact info at the very moment you are watching these screens. How awful!
Also, the app only requests 2 permissions to you on installing. This is another reason why people weren't skeptical and it's kind of hard to tell if it's fake app or not. It was so bold in its theft that users cannot be blamed.
Those who published this app were a famous group as spammers. The email addresses stolen from them will be used for sending out spam emails.
The conditions were attractive to trick users: it was placed in the popular saving battery-life genre, limited number of requesting permissions, and it uses Japanese language. I cannot help but to say that the group published this app were quite clever. Malicious, but clever.
These kinds of spywares and malwares tend to get more vicious and skilled every day. Please install a reliable security app to protect your smartphone!
Translation by Ruriko S.