Silent Night Zeus botnet available for sale in underground forums

Pierluigi Paganini May 23, 2020

Experts reported the existence of a botnet, tracked as Silent Night based on the Zeus banking Trojan that is available for sale in several underground forums.

This week researchers from Malwarebytes and HYAS published a report that included technical details on a recently discovered botnet, tracked as Silent Night, being distributed via the RIG exploit kit and COVID-19 malspam campaign. 

Silent Night

The source code of the Zeus Trojan is available in the cybercrime underground since 2011 allowing crooks to develop their own release since.

Experts found multiple variants in the wild, many of them belonging to the Terdot Zbot/Zloader malware family.

The name “Silent Night” Zbot is likely a reference to a weapon mentioned in the 2002 movie xXx, it was first spotted in November 2019 when a seller named “Axe” started offering it on the Russian underground forum forum.exploit[.]in.

Axe was advertising the Trojan as the result of over five years of work, a total of 15k ~ hours were spent for the development of the malicious code.

“The author described it as a banking Trojan designed with compatibility with Zeus webinjects. Yet, he claims that the code is designed all by him, based on his multiple years of experience – quote: “In general, it took me 5+ years to develop and support the bot, on average about 15k ~ hours were spent.”.” reads the report published by the researchers.

The botnet goes for $4,000 per month for a custom build, $2,000 per month for a general build, while an extra for HVNC functionality is available for 1,000 USD/month and 14 days to test the code for 500 USD.

Experts believe that Axe is the developer of the Axe Bot 1.4.1, comparing Axe Bot 1.4.1 and Zloader 1.8.0 C2 source codes, experts noted that all of their custom PHP functions have the prefix CSR, which can either be a naming space or a developer’s handle

Silent Night is able to grab information from online forms and perform web injections in major browsers, including Google Chrome, Mozilla Firefox, and Internet Explorer, monitor keystrokes, take screenshots, harvest cookies and passwords.

Silent Night leverages web injections to hijack a user’s session and redirect them to malicious domains or to grab the login credentials for online banking services. Data collected by the malware are then transferred to the operator’s command-and-control (C2) server.

The malware is able to infect all operating systems.

The seller also claims to use an original obfuscator, the decryption is performed only “on demand.” The analysis of the content of an open directory on the Command and Control server allowed the researchers to discover a manual for bot operators that includes instructions for the set up of the malware.

On Dec 23 2019, this variant of Zloader was observed being distributed by the RIG Exploit Kit, experts observed small campaigns, likely for testing purposes. The spreading intensified over time, in March 2020, it was delivered in a COVID-19-themed spam campaign using weaponized Word documents.

“The design of Silent Night is consistent and clean, the author’s experience shows throughout the code. Yet, apart from the custom obfuscator, there is not much novelty in this product. The Silent Night is not any game changer, but just yet another banking Trojan based on Zeus.” concludes the report. “Based on the analysis of the bot’s configurations, we may confidently say that there is more than one customer of the “Silent Night”.”

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Pierluigi Paganini

(SecurityAffairs – Silent Night, hacking)

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