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Blog — Jan 12, 2023

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

Gootloader Malware Leads to Cobalt Strike and Hand-on-Keyboard Activity

5 minutes read
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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?

Figure 1: Compromised WordPress site serving the initial payload

It is worth mentioning that the filenames and scheduled task name can be different even if the initial payload was downloaded from the same infected webpage.

The next stage of Gootloader (threat actor(s)’ hands-on activity)

The threat actor(s) retrieved and ran the Cobalt Strike payload zieu.ps1 from path appdata\roaming\btbh\.

Figure 2: Retrieved zieu.ps1 Cobalt Strike payload

After establishing the connection with the Cobalt Strike server (91.215.85[.]176), the threat actor(s) proceeded with retrieving and extracting BloodHound, a tool used for graphically analyzing Active Directory and other identity systems to identify attack pathways (20230103151757_bloodhound.zip) that contained pshound.ps1 under C:\Users\<username>.

After further analyzing the Windows Event Logs, we concluded that the script is similar to the one mentioned by GuidePoint Security that appears to be a BloodHound executable.

Besides the Cobalt Strike payload, the threat actor(s) retrieved the following files/tools:

Figure 3: Snippet of s5.ps1 script

The persistence via Registry Run Keys was created to run the PowerShell SOCKS proxy script with the following values:

Registry Run Key name: socks_powershell

Data (command to run): Powershell.exe -windowstyle hidden -ExecutionPolicy Bypass -File "C:\Users\\AppData\Local\s5.ps1"

The threat actor(s) removed most of the files they dropped on the host including the results produced by BloodHound as well as an unidentified krb.txt file dropped under C:\Users\.

After running BloodHound, the threat actor(s) attempted to move laterally by using PsExec to execute file rz.ps1 on a second host. This was not successful due to the PowerShell execution policy preventing execution of untrusted scripts. We were unable to retrieve the rz.ps1 script, but we assess it was likely a Cobalt Strike payload.

How did we find it?

What did we do?

What can you learn from this TRU positive?

Recommendations from our Threat Response Unit (TRU) Team:

Indicators of Compromise

Indicator Note
23d3d8cd3a5b8e4703a9b91970d790d1 zieu.ps1 (Cobalt Strike payload)
785fcb9380b4c2310c2200790641bc73 s5.ps1 (PowerShell SOCKS proxy)
cadb91ac90f52e27c0acae43b79aa202 son.ps1 (PowerShell SOCKS proxy)
bbbfab2763b717178141f0561584d087 contract salary calculator ontario 34123.js
hxxps[://]skymedia360[.]com/xmlrpc[.]php Contacted domain
hxxps[://]filorga[.]com/xmlrpc[.]php Contacted domain
hxxp[://]breadoflifetabernacle[.]com/xmlrpc[.]php Contacted domain
hxxps[://]lyngsfjord[.]com/xmlrpc[.]php Contacted domain
hxxps[://]galonivan[.]com[.]br/xmlrpc[.]php Contacted domain
hxxps[://]assistironline[.]net/xmlrpc[.]php Contacted domain
hxxps[://]dexacoin[.]net/xmlrpc[.]php Contacted domain
hxxps[://]thetripgoeson[.]com/xmlrpc[.]php Contacted domain
hxxps[://]hcss[.]nl/xmlrpc[.]php Contacted domain
hxxp[://]beechdesigngroup[.]com/xmlrpc[.]php Contacted domain
hxxp[://]dentalofficeathens[.]gr/xmlrpc[.]php Contacted domain
hxxp[://]aracelicolin[.]org[.]mx/xmlrpc[.]php Contacted domain
hxxps[://]shareddata[.]org/xmlrpc[.]php Contacted domain
hxxps[://]dunkandjump[.]com/xmlrpc[.]php Contacted domain
hxxps[://]nickthomm[.]com/xmlrpc[.]php Contacted domain
hxxps[://]1worldsync[.]com/xmlrpc[.]php Contacted domain
hxxps[://]hozoboz[.]com/xmlrpc[.]php Contacted domain
hxxps[://]burmancoffee[.]com/xmlrpc[.]php Contacted domain
hxxps[://]tonyevers[.]com/xmlrpc[.]php Contacted domain
hxxps[://]serialowy[.]pl/xmlrpc[.]php Contacted domain

eSentire’s Threat Response Unit (TRU) is a world-class team of threat researchers who develop new detections enriched by original threat intelligence and leverage new machine learning models that correlate multi-signal data and automate rapid response to advanced threats.

If you are not currently engaged with an MDR provider, eSentire MDR can help you reclaim the advantage and put your business ahead of disruption.

Learn what it means to have an elite team of Threat Hunters and Researchers that works for you. Connect with an eSentire Security Specialist.

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eSentire Threat Response Unit (TRU)
eSentire Threat Response Unit (TRU)

Our industry-renowned Threat Response Unit (TRU) is an elite team of threat hunters and researchers, that supports our 24/7 Security Operations Centers (SOCs), builds detection models across our Atlas XDR Cloud Platform, and works as an extension of your security team to continuously improve our Managed Detection and Response service. TRU has been recognized for its threat hunting, original research and content development capabilities. TRU is strategically organized into cross-functional groups to protect you against advanced and emerging threats, allowing your organization to gain leading threat intelligence and incredible cybersecurity acumen.