eSentire is The Authority in Managed Detection and Response Services, protecting the critical data and applications of 2000+ organizations in 80+ 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.
We provide sophisticated cybersecurity solutions for Managed Security Service Providers (MSSPs), Managed Service Providers (MSPs), and Value-Added Resellers (VARs). Find out why you should partner with eSentire, the Authority in Managed Detection and Response, today.
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?
At the beginning of January 2024, the eSentire Threat Response Unit (TRU) investigated a cryptojacking incident involving exploitation of a customer’s vulnerable Apache Tomcat server(Figure 1).
Figure 1: Infection process tree
The command shown above downloads the malicious script from 45.125.131[.]17 and uses “| sh” that pipes the output of the downloaded file directly into “sh”, a Unix shell, which executes the content of the downloaded file.
The downloaded file is a shell script (MD5: f63d58eba01f63cfd9ca24f2b390c4bc).
In Figure 2, the code is responsible for downloading a binary file from a remotehost. The code uses “wget” or “curl” to download a file named amd64 from the server specified at “HTTP_SERVER” and save it under “/tmp/.systemd-private-77435dd5909847103069367864234-color.service-vKDO4qY/”. The code introduces a random delay (RAND) before starting the download.
Figure 2: Snippet of code responsible for downloading coinminer binary
In the code below (Figure 3), the script attempts to create one of the following directories:
Figure 3: Code snippet responsible for creating directories
Once the directory is successfully created in any one of these locations, the script sets “PATH_BIN” to the path of this directory and exits the loop. If the script fails to create the directory in all three locations, it prints an error message and breaks out of the loop.
The code in Figure 4 is responsible for executing the downloaded binary with certain parameters:
stratum+tcp://ghostrider.jp.mine.zpool[.]ca:5354; this is the mining pool's server address
“- a ghostrider” specifies the mining algorithm. In this case, it’s ghostrider.
-u "$ADDRESS" sets the user's wallet address.
“-p c=BTC” specifies that the mining payouts should be in Bitcoin (BTC).
“--cpu-max-threads-hint=30” option instructs the mining software to use up to 30% of the CPU's maximum threads for mining to control resource usage.
Figure 4: Mining configuration
The code snippet in Figure 5 checks if a cron job involving the C2 server already exists. If not ($TEMP_CRON -eq 0), it creates a new cron job. The cron job is scheduled to run at a random minute every hour ($RAND_CRON). It uses curl or wget to download and execute the shell script from the server. The cron job is written to a temporary file named “Koajd.txt”, which is then added to the crontab and subsequently deleted.
The script then checks if there are fewer than three processes running that match certain criteria (involving "$ADDRESS" (coinminer address), amd64, and specific mining configuration). If the conditions are met ($TEMPxa2 -lt 3), it calls the “two_loop” function, which goes to the beginning of the shell script and produces the same steps we have described.
Figure 5: Snippet of the code responsible for setting up the cron job
Upon checking the BTC wallet address (referenced in Figure 6), it is observed that the current balance stands at approximately $333.
Figure 6: BTC wallet balance
What did we do?
Our 24/7 SOC Cyber Analysts investigated the incident and confirmed the activity is malicious.
Upon notification by our SOC of suspicious activities, the customer promptly acknowledged the alert and initiated an internal investigation into the incident.
What can you learn from this TRU Positive?
Attackers leverage unpatched vulnerabilities in widely used software like Apache Tomcat, emphasizing the need for timely updates and patch management.
The use of scripts for downloading and executing the coinminer, creating directories for persistence, and setting up cron jobs for continued operation demonstrates the methods used by attackers to maintain a presence on compromised systems.
The incident is an example of cryptojacking, where attackers use the resources of compromised systems for cryptocurrency mining, underlining the need for effective monitoring of system resources and network traffic for unusual activity.
Recommendations from our Threat Response Unit (TRU) Team:
Harden edge devices against compromise:
Replace default account credentials with unique ones.
Prioritize patching of vulnerabilities, particularly known exploited ones.
Protect endpoints (including servers) against malware by:
eSentire 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.
To learn what it means to have an elite team of Threat Hunters and researchers that works for you, connect with an eSentire Security Specialist now.
Indicators of Compromise
Name
Indicators
df2vGJJ58ivF
f63d58eba01f63cfd9ca24f2b390c4bc
C2
45.125.131[.]17
Pool’s server address
ghostrider.jp.mine.zpool[.]ca:5354
BTC wallet
bc1q8szxzvt4y2wzvew0x8mrgpkhf9dah5twx847wg
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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