That warning comes from Symantec, which reports a recent surge in Android apps available via the official Google Play store, which are designed by scammers to fool people who are seeking adult-oriented videos.
"We are now seeing multiple developers fiercely publishing apps in bulk on a daily basis," said security researcher Joji Hamada Monday in a blog post. "We have so far confirmed over 200 of these fraudulent apps published by over 50 developers, although it is likely that more exist. These apps have been downloaded at least 5,000 times in the last two months."
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The apps operate in the service of a scam that's known as one-click fraud, or one-click billing fraud. "In this scam, a person browsing the Internet is suddenly informed they have just agreed to pay a registration fee after simply clicking on a link," according to unrelated research published by a team at Carnegie Mellon University's Information Networking Institute. "They do not owe any money legally, but they pay the scammer out of feelings of shame for clicking on the link -- typically for pornographic material -- and to avoid further embarrassment if others were to mistakenly assume they subscribed to such material."
Geographically speaking, the good news -- for most people -- is that such attacks seem confined to the Japanese-language market, and the Carnegie Mellon team found that fewer than 10 criminal gangs appear to be behind such scams. The bad news for people snared by the scam, however, is that scammers can net 100,000 yen (about $1,000) in one go.
"One-click fraud is essentially unknown outside of Japan," according to research published last year by Trend Micro security researcher Jonathan Leopando. "Within Japan, however, it is frequent enough that government agencies keep track of cases that have been filed with their offices. Typically, around 400 new cases are reported every month. It is certain, however, that many other cases go unreported -- users may be afraid of going to law enforcement."
A more U.S.-focused variation on this type of scam is the Reveton malware, which freezes users' PCs and informs them that they must pay a fine to the FBI -- or some other law enforcement agency -- for viewing illicit or illegal material.
Although one-click fraud campaigns have long targeted PC users, Android malware designed for the same purpose was first spotted last year.
One cornerstone of the Android app security model is that users must authorize the types of behavior they'll grant to individual executables. But such defenses do little against one-click fraud scams. "Typically, the apps only require the user to accept the 'network communication' permission, although some variants do not require the user to accept any permissions," said Hamada. "This is because the app is simply used as a vehicle to lure users to the scam by opening fraudulent porn sites. The app itself has no other functionality. This may fool users into feeling safe about the app and catch them off guard when launching the app."
Still, Symantec said it's not clear how many people who downloaded the Japanese-language Android scamming apps would have ultimately paid up. "However, it appears to be worth the time and effort for the scammers as they have continued doing business for over two months," said Hamada.
Interestingly, Symantec has seen signs that some of the more than 50 developers behind the Japanese-language one-click fraud campaign have diversified into Android dating apps too. "It is not surprising to see scammers involved with both one-click fraud apps and dating service apps because these types of dating services are typically considered dodgy in Japan," said Hamada.
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