An emerging botnet is taking aim at banks and financial institutions, according to researchers at Palo Alto Networks.

The botnet, dubbed Jericho, is a variant of well-known banking Trojans such as Jorik, the researchers say. Palo Alto Networks' Wildfire analysis engine has detected more than 42 unique but related banking botnet samples that are part of an ongoing criminal enterprise aimed at stealing passwords and login credentials for financial institutions, they say.

Disassembly of the samples revealed well more than 100 domains targeted by the malware, most of which belong to banking and financial sites.

"Jericho’s background is somewhat interesting," Palo Alto Networks reports. "Infections were delivered from Israeli IP space; however the engineering of the file appears to be of Romanian origin. And there was actually a connection between the two: the vast majority of the URLs used to deliver the malware ended in ierihon [dot] com, and Ierihon is the word for Jericho in Romanian."

Jericho demonstrates a number of behaviors that are designed for stealth, persistence, and avoidance of traditional signature-based approaches to malware detection, the researchers say.

"The malware is able to inject itself into the Windows logon to maintain persistence on the infected host after a reboot," Palo Alto Networks states. "What was a bit more interesting was just how efficient the malware was at injecting itself into valid applications such as Firefox, Chrome, Java, Outlook and Skype, and then repurpose their capabilities. This not only enables the malware to hide within approved applications during run time, but it also means that standard methods for observing Windows API calls are subverted. This allows for a more stealth presence in the system."

Using a combination of a stealthy program and piggybacking on common applications, Jericho has avoided the scrutiny of most antivirus vendors, the researchers said.

"Of the 42 samples analyzed by Palo Alto Networks, the top AV solutions only achieved a 3.2 percent detection rate on the day [of discovery]," Palo Alto Networks says. Twelve of the 42 signatures were not detected at all over a seven-day span.

"This trend seems to indicate that this particular criminal operation is cognizant of the AV coverage for their malware, and has established a delivery strategy that minimizes collection by AV vendors," the researchers say.

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