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AutoIt Delivering Vidar Stealer Via
Drive-by Downloads

BY eSentire Threat Response Unit (TRU)

June 6, 2024 | 4 MINS READ


Threat Intelligence

Threat Response Unit

TRU Positive/Bulletin

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Adversaries don’t work 9-5 and neither do we. At eSentire, our 24/7 SOCs are staffed with Elite Threat Hunters and Cyber Analysts who hunt, investigate, contain and respond to threats within minutes.

We have discovered some of the most dangerous threats and nation state attacks in our space – including the Kaseya MSP breach and the more_eggs malware.

Our Security Operations Centers are supported with Threat Intelligence, Tactical Threat Response and Advanced Threat Analytics driven by our Threat Response Unit – the TRU team.

In TRU Positives, eSentire’s Threat Response Unit (TRU) provides a summary of a recent threat investigation. We outline how we responded to the confirmed threat and what recommendations we have going forward.

Here’s the latest from our TRU Team…

What did we find?

In May 2024, eSentire’s Threat Response Unit (TRU) detected an attack involving a fake KMSPico activator tool, which delivered Vidar Stealer through a series of events. The attack leveraged Java dependencies and a malicious AutoIt script to disable Windows Defender and, finally, decrypt the Vidar payload via the shellcode.

In the observed incident, the user performed a web search for KMSPico and browsed to the top result (kmspico[.]ws). The tool is marketed as a “universal activator” for Windows and appears to no longer be maintained.

The kmspico[.]ws site is hosted behind Cloudflare Turnstile and requires human input (entering a code) to download the final Zip package. These steps are unusual for a legitimate application download page and are done to hide the page and final payload from automated web crawlers.

Figure 1: Malicious webpage serving the payload

The ZIP archive in our analysis contains Java dependencies and the malicious executable Setuper_KMS-ACTIV.exe (MD5: 6b6d562c71b953f41b6915998f047a30).

Upon launching the executable, javaw.exe will start, which is responsible for disabling behavior monitoring in Windows Defender and dropping the malicious AutoIt script named “x” (MD5: c7ece036a2284fba0f5d31055b44846f) along with AutoIt named Flour.pif (MD5: b06e67f9767e5023892d9698703ad098).

The AutoIt script contains the encrypted Vidar payload (Figure 2) that will be injected into the current running AutoIt process.

Figure 2: Snippet of the encrypted Vidar payload

The shellcode is responsible for decrypting the Vidar payload using the RC4 decryption algorithm (Figure 3) with an obfuscated hardcoded key in the malicious AutoIt script.

Figure 3: RC4 PRGA (Pseudo-Random Generation Algorithm) within the shellcode

Vidar Stealer uses Telegram for the Dead Drop Resolver (DDR)to store the C2 IP address, as shown in Figure 4.

A Dead Drop Resolver is used by threat actors to host command and control (C2) information on legitimate external web services, embedding and often obfuscating domains or IP addresses within content posted on sites and popular applications such as Telegram and Stealer, thus concealing the C2 infrastructure (T1102.001).

Figure 4: Telegram as a DDR

This incident is a reminder that malware-laden applications (particularly greyware piracy tools) are hidden in plain sight among web search results and stresses the importance of user awareness to guard against such threats.

What did we do?

Our team of 24/7 SOC Cyber Analysts isolated the affected host and notified the customer of suspicious activities, providing additional support and remediation.

What can you learn from this TRU Positive?

Recommendations from our Threat Response Unit (TRU):

We recommend implementing the following controls to help secure your organization against Vidar Stealer malware:

Indicators of Compromise

You can access Indicators of Compromise here.

eSentire Unit
eSentire Threat Response Unit (TRU)

The eSentire Threat Response Unit (TRU) is an industry-leading threat research team committed to helping your organization become more resilient. TRU is an elite team of threat hunters and researchers that supports our 24/7 Security Operations Centers (SOCs), builds threat detection models across the eSentire XDR Cloud Platform, and works as an extension of your security team to continuously improve our Managed Detection and Response service. By providing complete visibility across your attack surface and performing global threat sweeps and proactive hypothesis-driven threat hunts augmented by original threat research, we are laser-focused on defending your organization against known and unknown threats.

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