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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…
PaperCut, a print management software provider, announced two critical vulnerabilities in March 2023:
Although both vulnerabilities were originally reported to PaperCut in January 2023 and patched in March 2023, they have been widely exploited in April 2023.
PaperCut NG/MF allows network administrators to manage print jobs, specifically who can print and whether the user has enough allocated credits. This requirement is typically found in educational institutions where students are allotted a set number of credits for print jobs.
PaperCut NG/MF uses an application server to intercept and process print jobs. It also provides an Admin web interface for administrators to remotely configure and manage the system.
In a typical scenario, an attacker could exploit CVE-2023–27350 by visiting the “SetupCompleted” page on the PaperCut MF/NG web interface (described here) to bypass authentication and log in as an administrator. Once authenticated, command execution can be achieved using print scripts via the web interface.
Exploitation of CVE-2023–27350 by Cryptocurrency Miner Botnet
On April 22, eSentire MDR for Endpoint alerted our SOC of unusual PowerShell activity on the server of a customer in the education sector.
A subsequent investigation confirmed this activity was tied to exploitation of CVE-2023–27350 against the customer’s public-facing PaperCut web interface.
The coinminer deployment followed standard tradecraft for this class of threat. The first stage batch file me1.bat (MD5: a3ffb336aee9f01275c92ac529c8f70e) kills existing mining processes and persistence mechanisms and attempts to disable Windows Defender.
The batch file then retrieves and executes a second batch file me2.bat (MD5: 5d32f0eee7adf20e0766d5481a1953a5).
The second batch file handles installing XMRIG miner on the system. Me2.bat is a slightly modified version of https://github.com/MoneroOcean/xmrig_setup/blob/master/setup_moneroocean_miner.bat, where xmrig.exe is renamed to dom.exe and written to %USERPROFILE%\dom. The miner uses key wallet id 43DTEF92be6XcPj5Z7U96g4oGeebUxkFq9wyHcNTe1otM2hUrfvdswGdLHxabCSTio7apowzJJVwBZw6vVTu7NoNCNAMoZ4 and retrieves a zip package from http://50.19.48[.]59. This package contains the necessary binaries and configuration files for running the Monero miner.
Non-Sucking Service Manager, renamed to dsm.exe is used to create a service for the miner binary.
There are several references to “mimu” within the setup file. For example the script prepends the string “mimu.” to the hostname and configures the miner pool to update.mimu-me[.]cyou:80. Interesting this domain resolves to 22.214.171.124, an IP previously seen in association with exploitation of Atlassian Confluence Vulnerability CVE-2022-26134 to deploy coin miners.
“Mimu” is likely a reference to the Mimu/Mimo Miner botnet. The wallet id mentioned above and overall deployment behavior aligns with community reporting from previous critical vulnerabilities in Log4J.
Other public mentions of this recent campaign suggest the operators behind this botnet attempted to widely exploit CVE-2023–27350 around mid-to-late April 2023.
Public and private educational institutions that rely on PaperCut may be targeted for exploitation if their application is vulnerable. We highly recommend immediately checking to see if their application has been compromised. In addition, eSentire TRU also recommends:
Monero Miner Pool
mimu-me[.]cyou DNS A Record Value
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.
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.