A Trojan spotted earlier this year targeting banks in the Czech Republic has expanded its target list and become more global.
According to researchers at Avast, an analysis of the payload for the Rig Exploit kit identified a payload known as Tinba that is targeting financial institutions across the world, including Bank of America, HSBC and ING Direct.
Also known as the Tinybanker Trojan, the malware is being delivered via sites infected by the exploit kit, which targets vulnerabilities in Adobe Flash Player and Microsoft Silverlight, explained Avast virus analyst David Fiser. If the user’s system is vulnerable, the exploit executes malicious code that downloads and executes the Tinba Trojan.
When the infected user tries to log in to one of the targeted banks, webinjects are used to trick the victim into filling out a form with his or her personal data – including social security numbers, address and credit card information. If the victim does this, the data is sent to the attackers.
“In the case of the Tinba “Tiny Banker” targeting Czech users, the payload was simply encrypted with a hardcoded RC4 password,” Fiser blogged. “However, in this case, a few more steps had to be done.”
At first, the researchers located the folder with the installed banking Trojan, Fiser continued. This folder contained an executable file and the configuration file.
“At first, XOR operation with a hardcoded value 0xac68d9b2 was applied,” he explained. “Then, RC4 decryption with hardcoded password was performed. After RC4 decryption, we noticed AP32 marker at the beginning of the decrypted payload, which signalized aplib compression. Therefore, after aplib decompression, we got the configuration file in plaintext. After studying this roughly 65KB long plaintext file, we noticed that it targets financial institutions worldwide.”
The malware was first identified back in 2012 hitting targets in Turkey. At the time, it was linked to the Blackhole exploit kit. It was given the name Tinybanker/Tinba because of its small size – approximately 20 KB. The most recent changes come two months after reports surfaced that its source code had been leaked on to the Internet.
