Scam artists seeking to capitalise on the demise of popular mobile game Flappy Bird have released harmful clones.
Apps that appeared to be identical to the original have been designed to trick users into sending premium rate text messages.
The malicious apps were found in Google's Android store, security firm Trend Micro reported.
The real Flappy Bird creator said he deleted the app as it was "addictive".
In an interview with Forbes, the "stressed" 29-year-old developer Dong Nguyen said: "Flappy Bird was designed to play in a few minutes when you are relaxed.
"But it happened to become an addictive product. I think it has become a problem. To solve that problem, it's best to take down Flappy Bird. It's gone forever."
Quick to seize an opportunity, scammers have created clone apps containing malicious software.
"All of the fake versions we've seen so far are premium service abusers - apps that send messages to premium numbers, thus causing unwanted charges to victims' phone billing statements," a blog from Trend Micro explained.
"The fake Flappy Bird app asks for the additional read/send text messages permissions during installation - one that is not required in the original version."
The fake apps were most prominent in stores targeted at users in Russia, the company said, as well as Mr Nguyen's home country of Vietnam.
Trend Micro added: "Apart from premium service abuse, the app also poses a risk of information leakage for the user since it sends out the phone number, carrier, Gmail address registered in the device."
Unsurprisingly, many clones - malicious or otherwise - have rushed to take Flappy Bird's place at the top of app store charts.
Among them, Ironpants - a game with a similar premise that was already proving popular before Flappy Bird was taken down.
Slightly less subtle clones included Clumsy Bird, Flappy Fish, Flappy Octopus and Flappy Angry Bird.
Sites where companies can post offers of freelance work are awash with requests for Flappy Bird clones to be made quickly.
Some have speculated that Flappy Bird would return soon, and that Mr Nguyen had carried out a masterstroke of viral marketing.
Others speculated that legal issues were behind the decision to take the game down, but Mr Nguyen denied this - as did Nintendo, who some suspected of applying legal pressure due to the pipes in Flappy Bird resembling those found in early Super Mario titles.
However, the developer said that the game's success and the attention it had brought him had meant he was losing sleep.