Malware that can successfully outwit the CAPTCHA image recognition system has been detected.
According to Kaspersky Lab, the Trojan-SMS.AndroidOS.Podec has developed a technique to convince CAPTCHA that it is a person in order to subscribe thousands of infected Android users to premium-rate services.
Initially detected in late 2014, Podec automatically forwards CAPTCHA requests to a real-time online human translation service that converts the image to text using an online image-to-text recognition service and within seconds, the text from the CAPTCHA image is recognised by a person and the details are relayed back to the malware code, which can then proceed with execution.
Podec targets Android device users primarily through Russia’s popular social network, Vkontakte, with most victims to date detected in Russia and surrounding countries. Infection generally occurs through links to supposedly cracked versions of popular computer games, which 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. Upon infection, the Podec malware requests administrator privileges that, once granted, make it impossible to delete or halt the execution of the malware.
Victor Chebyshev, non-intel research group manager at Kaspersky Lab, said: “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 specialising in fraud and illegal monetisation.”
In an email to IT Security Guru, Lancope CTO, TK Keanini, said that this is a great example of how security is a game of innovation with each side co-evolving with one another.
He said: “In all defensive measures it is only a matter of time before they are defeated through the innovation of the attacker. The defender then must go back and innovate more countermeasures and round and round we go.
“The reason we will see more machine-to-machine attacks is because of the fact that there are just more machine-to-machine communications in architectures these days, driven by the growth cloud infrastructure supporting mobile and also by IoT architecture.
“We must go back and remember why CAPTCHA countermeasures were invented. Originally a countermeasure to kill attackers’ automation and force them to scale back to manual and human assisted techniques. In other words, successful machine to machine automation needed to be defeated in this stage of the process.”
Wim Remes, manager of strategic services EMEA at Rapid7, said: “By using a live, online human translation service, Podec doesn’t make the services believe it is human, it is actually human. Podec does not use an innovative attack method, the user still needs to download the application himself and grant privileges to it.
“The lessons we are reminded of once again are as simple as they are worth repeating: Do not be tempted by offers that seem too good to be true. Only download products from reputable application stores and review privileges applications request upon installation.”
