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Carberp Trojan Goes Mobile: 'Citmo' Found Targeting Russian Banks

Carberp, a banking fraud Trojan, now has a variant that targets Android devices, researchers have found.

Carberp-in-the-mobile, or “Citmo”, is primarily targeting Russian banks and financial institutions in Russian-speaking countries, according to Kaspersky Lab. Citmo joins the ranks of Zeus-in-the-mobile (Zitmos) and SpyEye-in-the-mobile (Spitmos) in targeting SMS messages sent by banks to authenticate online banking transactions.

"The CitMo Android Trojan works in almost the same way as ZitMo," Maslennikov wrote, adding it can hide particular SMS messages, or resend them to the attacker's command server or to other phone number.

CarberpThe attacks begin by infecting the user's PC. The banking Trojan modifies the online banking site by injecting fields and text instructing users to download an install a mobile app on to the user's smartphone as part of the enhanced security measures. Users download and install the app, thinking they are complying with security requirements.

"If a user tries to login into his online banking account using a machine infected by Carberp, the malware will modify the transaction so that user credentials are sent to a malicious server rather than a bank server," Maslennikov noted on Kaspersky Lab's Securelist blog.

When the user initiates a transaction during an online banking session, the bank sends a SMS transaction authorization code to the user's mobile device. The malicious app the user had previously installed intercepts that message, giving criminals the access code to illegally transfer funds. The user may see a "temporarily unavailable" message or think the transaction is going through, but in reality, the criminals are actually using the mTAN to conduct their own transactions.

The app developer, going by the name of Samsonov Sergey, had uploaded three Citmo apps to Google play, but all three have been removed by Google. The apps SberSafe, AlfaSafe, and VkSafe targeted popular Russian banks.

The gang behind Carberp has been busy. Russian security firm Group-IB reported the creators of Carberp have started to sell an improved version of the malware kit with custom scripts targeting online banking customers. The Web injects target sites of major North American banks such as Wells Fargo, Citibank, JPMorgan Chase, Bank of America, and TD Bank, Group-IB said.

Team Carberp has also decided to put Carberp back on the market. Back in February 2011, it charged $10,000 for a complete version of the Trojan, with the builder and a VNC access module, to a limited number of customers for $10,000. After a month, the team had stopped sales because it had "sold to enough new users" and the malware was taken off the market.

The Trojan is now available again, although as a monthly subscription-based model with prices ranging between $2,000 and $10,000, Limor Kessem, cyber-crime and online fraud communications specialist, wrote on the RSA FraudAction Research Labs blog. The price varies on the number of modules being purchased.

For a one-time fee of $40,000, the buyer can obtain a builder application for a specialized Carberp version that contains a bootkit component.

"At no point in cyber-crime history has any developer asked such price for a banking Trojan," Kessem said.

Compared to the truly commercial malware, such as Zeus, SpyEye, Citadel, Carberp is not as widely spread in the wild since it has been kept private most of its existence, Kessem said. That's changing, as the team is beginning to sell to "new and un-vouched for users," which will open the door for brand new botmasters launching Carberp attacks.

However, it's still comparatively high price tag will still keep Carberp's sophisticated features "out of reach for common cybercriminals," Kessem said.

"This latest version of the Carberp Trojan may confirm that the highest levels of cybercrimeware are still reserved for the elite and privileged few; malware does not come with an installation wizard—yet," Kessem wrote.

Fahmida Y. Rashid is a Senior Contributing Writer for SecurityWeek. She has experience writing and reviewing security, core Internet infrastructure, open source, networking, and storage. Before setting out her journalism shingle, she spent nine years as a help-desk technician, software and Web application developer, network administrator, and technology consultant.