Podec: First Trojan to trick CAPTCHA into thinking its human

CAPTCHA has long been considered to be very safe online, but a new trojan detected by security analysts can trick CAPTCHA into thinking its human.

Published Date
11 - Mar - 2015
| Last Updated
11 - Mar - 2015
Podec: First Trojan to trick CAPTCHA into thinking its human

Kaspersky Lab’s security analysts have discovered first malware to successfully outwit the CAPTCHA image recognition system. The Trojan-SMS.AndroidOS.Podec has developed a technique to convince CAPTCHA it is a person in order to subscribe thousands of infected Android users to premium-rate services.    

First detected in late 2014 and updated since then, Podec automatically forwards CAPTCHA requests to a real-time online human translation service that converts the image to text.  It can also bypass the Advice on Charge system, which notifies users about the price of a service and requires authorization before payment.  The Trojan’s goal is to extort money from victims via premium-rate services.

According to data collected with the help of the Kaspersky Security Network, Podec targets Android device users primarily through Russia’s popular social network, VKontakte (VK, vk.com). Other sources discovered by Kaspersky Lab include domains with the names of Apk-downlad3.ru and minergamevip.com. Most victims to date have been detected in Russia and surrounding countries.
Infection generally occurs through links to supposedly cracked versions of popular computer games, such as Minecraft Pocket Edition. These links appear on group pages and victims are drawn in by the lack of cost and what appears to be a far lower file size for the game when compared to the legitimate version. Upon infection, the Podec malware requests administrator privileges that, once granted, make it impossible to delete or halt the execution of the malware.

According to Kaspersky, “CAPTCHA image recognition requests are increasingly added to online forms to ensure the request is submitted by a person and not automated software. Podec passes CAPTCHA by redirecting the CAPTCHA processor to an online image-to-text recognition service, Antigate.com.  Within seconds the text from the CAPTCHA image is recognized by a person and the details are relayed back to the malware code, which can then proceed with execution.”

 “Podec marks a new and dangerous phase in the evolution of mobile malware.  It is devious and sophisticated. The social engineering tools used in its distribution, the commercial-grade protector used to conceal the malicious code and the complicated process of extortion achieved by passing the CAPTCHA test - all lead us to suspect that this Trojan is being developed by a team of Android developers specializing in fraud and illegal monetization. It is clear that Podec is being further developed, possibly with new targets and goals in mind and we urge users to be wary of links and offers that sound to good to be true,” said Victor Chebyshev, Non-Intel Research Group Manager at Kaspersky Lab.

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