Gozi IFSB banking Trojan has rolled out new code, a new botnet and a high level of customization in the latest wave of attacks.

Gozi IFSB, a banking Trojan that has been making the rounds of the internet for several years, is back with new targets, new characteristics, and a new botnet for distribution. The changes, detailed by Talos Intelligence on Tuesday, serve to make the Trojan a more dangerous threat to a select group of victims.

Gozi IFSB has begun to use the Dark Cloud botnet in recent campaigns, a development that shows the attackers are moving to infrastructures that are associated with widespread criminal and malicious activity. Dark Cloud, which uses compromised personal computers as hosts for websites that change addresses every few minutes, is based primarily in Eastern Europe and Russia.

The most recent campaign uses individually targeted email messages with malicious Microsoft Word files as the delivery mechanism for the malware payload. 

"It's likely they built emails to resemble realistic email threads, appearing to reply to a victim’s previous question or request," says Talos threat researcher Holger Unterbrink, in an email interview with Dark Reading. "In other cases, they crafted email messages that are somehow related to the victims interests such as company-related information."

The level of customization indicates a high level of human involvement with the messages, rather than a mass spam email campaign. "We believe that they are using an obfuscator script/program. In many cases we looked at, they built different obfuscated docs for every single victim," says Unterbrink.

While there are a variety of different malicious payloads attached to the delivery systems, almost all are based on VBA scripts that use various methods of obfuscation and different execution patterns in attempts to evade detection in sandbox environments. Sophisticated current sandboxes and malware detection routines would almost certainly detect the activity, but simple or older technology could easily miss the operations.

Given the new payload and delivery mechanisms, what should organizations do to protect themselves from the latest wave of Gozi IFSB? "Use a multi-layer security architecture approach," says Unterbrink. "This means a mix of security protection devices/applications which are capable of communicating with each other. Companies need to realize that some attackers are using extremely sophisticated methods and/or rely on victims making mistakes (e.g. opening phishing emails). In a multi layer protected environment, even the side effects of successful attacks can be detected."

"Another important recommendation," he says, "is to focus on user education. Setup [sic] fake phishing campaigns or buy similar services to make your user aware of this threat."

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About the Author(s)

Curtis Franklin, Principal Analyst, Omdia

Curtis Franklin Jr. is Principal Analyst at Omdia, focusing on enterprise security management. Previously, he was senior editor of Dark Reading, editor of Light Reading's Security Now, and executive editor, technology, at InformationWeek, where he was also executive producer of InformationWeek's online radio and podcast episodes

Curtis has been writing about technologies and products in computing and networking since the early 1980s. He has been on staff and contributed to technology-industry publications including BYTE, ComputerWorld, CEO, Enterprise Efficiency, ChannelWeb, Network Computing, InfoWorld, PCWorld, Dark Reading, and ITWorld.com on subjects ranging from mobile enterprise computing to enterprise security and wireless networking.

Curtis is the author of thousands of articles, the co-author of five books, and has been a frequent speaker at computer and networking industry conferences across North America and Europe. His most recent books, Cloud Computing: Technologies and Strategies of the Ubiquitous Data Center, and Securing the Cloud: Security Strategies for the Ubiquitous Data Center, with co-author Brian Chee, are published by Taylor and Francis.

When he's not writing, Curtis is a painter, photographer, cook, and multi-instrumentalist musician. He is active in running, amateur radio (KG4GWA), the MakerFX maker space in Orlando, FL, and is a certified Florida Master Naturalist.

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