Banking Trojan “Brolux” Targets Users in Japan

A new banking Trojan dubbed “Brolux” has been spotted targeting online banking users in Japan, researchers at ESET have warned.

According to the security firm, the threat, detected as Win32/Brolux.A, has been distributed by malicious actors with the aid of a Flash Player exploit leaked as a result of the Hacking Team breach (CVE-2015-5119) and an Internet Explorer vulnerability dubbed “Unicorn” (CVE-2014-6332).

The Flash Player flaw was patched by Adobe in July and the Unicorn bug was addressed by Microsoft in November 2014, but it appears even older exploits like these can be useful for delivering malware.

ESET says the exploits have been hosted on an adult website and there is no indication that any exploit kits have been used to distribute Brolux. If the exploits are successful, a signed binary is pushed to the victim’s device.

Once it infects a computer, the Trojan’s main payload downloads two configuration files: one containing a list of 88 URLs, and one containing a list of browser window titles associated with Internet banking in Japan.

The malware monitors the websites visited by the user in search for online banking sites. If the victim uses Internet Explorer, Brolux compares the visited site’s URL with the URLs in the first configuration file. If Firefox or Chrome are used, the threat compares the window’s title with the list from the second configuration file.

If the URLs or window titles match, a new process is created and the victim is pointed to a phishing page designed to harvest login information, security questions and answers, payment card data, passwords, email addresses and passwords, and PINs. In order to make everything look legitimate, the phishing pages are designed to appear as if they are associated with the Japanese Public Prosecutors Office and the Financial Services Agency (FSA).

ESET researchers have uncovered clues suggesting that Chinese cybercriminals might be behind this Brolux attack. For example, one of the samples uses a Chinese mutex name, the phishing pages also contain text written in Chinese, and the malware is signed with a certificate issued to a Chinese company. The certificate was previously used to sign other malware, including a banking Trojan aimed at users in Korea, and potentially unwanted applications (PUAs).

Several pieces of malware have been used over the past period to target the customers of Japanese banks, including Shifu, Neverquest and Tsukuba. However, Trend Micro highlighted in a report published this week that the Japanese cybercriminal underground is still in its infancy.

“Although our observations reveal that Japanese cybercriminals lack the technical know-how needed for malware creation, the interest is there, as evidenced by exchanges on how to monetize malware tools purchased from other regional underground markets,” Trend Micro experts said. “Once enterprising individuals discover the feasibility of making money using hacking or malware, we may see more locally produced hacking tools and tips on Japanese underground sites.”