A new and improved version of Tinba, a banking malware known for its small size, has been spotted in attacks targeting the customers of European financial institutions.
Tinba, also known as Tinybanker and Zusy, was first spotted by researchers in mid-2012. Similar to other banking Trojans, Tinba uses man-in-the-browser (MitB) tactics and web injects to collect valuable information from victims.
In May, researchers at IBM Security noticed a campaign involving a new variant of the malware. Experts have spotted infections in Poland, Italy, Germany and the Netherlands.
Once it infects a computer, the malware waits for the victim to visit one of the targeted banking websites. When such a website is accessed, web injects are triggered and victims are presented with a bogus message designed to trick them into handing over personal and financial information that the cybercriminals can use to conduct fraudulent transactions.
One of the messages spotted by IBM researchers informed users that their account had been locked due to some money being accidentally transferred to it. Victims were instructed to refund the money in order to have the account unlocked.
According to researchers, the new Tinba version has some interesting fallback mechanisms designed to protect the botnet against hijacking and takedowns.
The list of features includes public key signing to ensure that only authorized botmasters can send commands and updates to the Trojan, update server authentication when receiving new configuration data, and a machine-dependent encryption layer for each bot to prevent spoofing by researchers. Experts also noted that bots are designed to communicate with hardcoded resource URLs, but if necessary they can fall back to URLs from a domain generation algorithm (DGA).
One of the first countries targeted by Tinba was Turkey, where more than 60,000 unique infections were identified during a 2012 campaign.
Over the past years, the malware, whose source code has been leaked, has considerably expanded its target list. In September 2014, researchers at Avast reported that the Trojan had gone global, targeting financial organizations such as US Bank, Bank of America, HSBC, TD Bank, Chase, Fifth Third Bank, Wells Fargo, Banco de Sabadell, Regions, ING, RBC Royal Bank, CitiBank, Westpac, and others.