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Exploring the Infection Chain: ScreenConnect’s Link to AsyncRAT Deployment

BY eSentire Threat Response Unit (TRU)

July 3, 2024 | 5 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 June 2024, eSentire’s Threat Response Unit (TRU) observed several incidents involving users downloading the ScreenConnect remote access client. ScreenConnect is a remote access tool that can allow unauthorized access to a user's system if exploited by threat actors. We assess with medium confidence that the initial infection vector was a drive-by download.

This occurred when users visited a deceptive site that redirected them to download the ScreenConnect application automatically. With the established session via ScreenConnect, the threat actor dropped an executable file that eventually led to the infection of AsyncRAT, which is a remote access trojan (Figure 1).

Based on a review of available logs, we determined that the user in one case downloaded the ScreenConnect instance from a compromised WordPress site aviranpreschool[.]com, which was redirected from lomklauekabjikaiwoge[.]com. When launched, ScreenConnect connected to threat actor’s instance at fa-histsedueg.screenconnect[.]com.

Figure 1: Infection chain

As mentioned previously, using ScreenConnect, the threat actor dropped the executable file uy5a7ykit5s7xs7isi9i.exe (MD5: 6bdba391a77bb67cb5aaae203d061ea8).

The executable is an NSIS installer that contains an NSI script and embedded AutoIt components and batch scripts.

The NSI script is responsible for executing the batch file named “Industries.cmd” (MD5: 3f8ca557d51e210952bdd7180cb33d10) (Figure 2).

Figure 2: The contents of the "Industries" batch file

The Industries.cmd batch file performs the following actions:

The script also checks for processes such as avastui.exe (Avast antivirus software), avgui.exe (AVG AntiVirus), nswscsvc.exe (Norton Security), and sophoshealth.exe (Sophos endpoint). If any of these processes are found, it executes a malicious AutoIt script using the original AutoIt executable. It's possible this step is taken to evade detection for renamed binaries by these AV agents.

The malicious AutoIt script is responsible for decrypting the embedded AsyncRAT payload via RC4 and subsequently injecting it into either RegAsm.exe or AppLaunch.exe if bdagent.exe (Bitdefender Agent) is detected as a running process. You can access the configuration for the AsyncRat payload on our GitHub page.

In conclusion, the June 2024 incidents analyzed by eSentire's Threat Response Unit illustrate how threat actors utilized the ScreenConnect client to establish unauthorized remote sessions. By deceiving users into downloading ScreenConnect via misleading websites, the attackers gained remote access and subsequently deployed the AsyncRAT trojan.

What did we find?

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:

Indicators of Compromise

You can access the 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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