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Nov 22, 2021
Microsoft Exchange Vulnerability - CVE-2021-42321
THE THREAT eSentire has identified publicly available Proof-of-Concept (PoC) exploit code, for the critical Microsoft Exchange vulnerability CVE-2021-42321. CVE-2021-42321 was announced as part of Microsoft’s November Patch Tuesday release. Exploitation would allow a remote threat actor, with previous authentication, to execute code on vulnerable servers. Prior to the patch release, Microsoft…
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eSentire is The Authority in Managed Detection and Response Services, protecting the critical data and applications of 1000+ organizations in 70+ countries from known and unknown cyber threats. Founded in 2001, the company’s mission is to hunt, investigate and stop cyber threats before they become business disrupting events.
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Telarus and eSentire Expand Partnership to Safeguard Enterprises Globally Against Business Disrupting Ransomware and Zero-Day Attacks
London, UK and Sydney, Australia– Oct. 28, 2021 - eSentire, recognized globally as the Authority in Managed Detection and Response (MDR), today announces the expansion of its partnership with Telarus, the largest privately-held distributor of business cloud infrastructure and contact centre services. Building on their mutual success across North America, Telarus will bring eSentire’s Managed…
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Blog — Oct 25, 2021

TRU Positives: Weekly investigation summaries and recommendations from eSentire’s Threat Response Unit (TRU)

Years Old Infection Discovered After Installing the eSentire MDR for Endpoint Agent

Speak With A Security Expert Now

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?

Figure 1 PowerShell script which re-assembles folder names into a working script.

Figure 2 Directory listing showing encoded folder names used by PNRP.ps1 to form a new PowerShell command.

Figure 3 CyberChef recipe demonstrating the decoding process.

The antivirus coverage for the initial PowerShell script residing on disk is minimal since the malicious content is loaded dynamically from directory filenames during runtime:

Figure 4 VirusTotal results for the first stage PowerShell script.

Figure 5 The final re-assembled PowerShell command. Executes code from a remote source and disables AV protections.

How did we find it?

Our Machine Learning PowerShell classifier identified the persistence mechanism utilized by the threat actors after our endpoint agent was installed on the system.

What did we do?

What can you learn from this TRU positive?

Figure 6 The multi-stage PowerShell execution from the endpoint perspective. Note the final command is easily readable.

Recommendations from our Threat Response Unit (TRU) Team:

Ask Yourself…

If you’re not currently engaged with a Managed Detection and Response provider, we highly recommend you partner with us for security services in order to disrupt threats before they impact your business.

Want to learn more? Connect with an eSentire Security Specialist.

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