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Tsukuba Banking Trojan Targets Users in Japan

Researchers at IBM Trusteer have come across a new banking Trojan that is designed to target the customers of Japanese financial institutions.

Dubbed “Tsukuba” after the Japanese city, the malware is not very sophisticated from a technical standpoint, but its social engineering engineering techniques make it highly efficient in harvesting personal and financial information, researchers said.

Tsukuba is a proxy changer malware that hijacks victims’ browsers in an effort to redirect them to malicious websites.

The Trojan is distributed through spam emails. Once it’s executed, the threat leverages the Windows PowerShell scripting tool to hide its presence while it communicates with the command and control (C&C) server and downloads components.

In order to evade detection and prevent researchers from analyzing it, Tsukuba scans the list of running processes to see if any proxy detection tools or virtualization software are present. If such applications are detected, the malware stops the installation process.

If the presence of a virtual environment is not detected, the Trojan copies browser cookies and checks them to see if the victim has visited any of the targeted financial websites. This allows the cybercriminals to determine if it’s worth infecting the machine.

Once it’s installed on a device, the malware creates a malicious Proxy Auto-Config (PAC) file so that Web browser such as Firefox, Chrome and Internet Explorer redirect victims to the attackers’ URLs. The attackers don’t want to waste any resources on non-Japanese users so only individuals browsing from a Japanese IP address are directed to phishing pages, while others are presented with an error message.

IBM researchers have pointed out that unlike traditional phishing pages, the ones set up by the cybercrooks behind Tsukuba are highly customized and interactive.

“The look and feel is dynamically pulled from the legitimate bank’s portal, and the fake pages actually interact with the victim via pop-ups. In Tsukuba’s case, after victims enter their credentials, the pop-ups proceed to ask them for personal details and to upload clear images of their official documentation and passport,” IBM Trusteer threat engineer Dani Abramov explained in a blog post. “Looking at similar malware of Tsukuba’s grade, this extensive social engineering component definitely goes far beyond the common.”

In order to avoid raising suspicion when victims access the fake banking sites through the rogue proxy, the attackers install a root certificate on the infected machine.

Once a user’s information is harvested, the proxy settings are restored. In case victims become suspicious, they will not be able to reach the phishing page for a second time, and instead they will be presented with the legitimate website.

There aren’t many banking Trojans designed to target users in Japan, partly because it’s easier for cybercriminals to create phishing pages and spam emails written in English than it is in Japanese. Many users don’t expect to be targeted in such attacks, which makes them more likely to fall for the tricks employed by Tsukuba.

Last year, the security industry and law enforcement conducted several operations aimed at disrupting financial malware. As a result, according to Symantec, the number of financial Trojans dropped by 53% and the number of traditional phishing emails dropped by 74% in 2014.

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Eduard Kovacs (@EduardKovacs) is a contributing editor at SecurityWeek. He worked as a high school IT teacher for two years before starting a career in journalism as Softpedia’s security news reporter. Eduard holds a bachelor’s degree in industrial informatics and a master’s degree in computer techniques applied in electrical engineering.