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Cryptomining malware is one of the most common outcomes of a compromised VPS — attackers use hijacked server resources to mine cryptocurrency, often for extended periods before detection. This guide covers identifying and remediating this specific threat.

Signs of a Cryptomining Infection

• Sustained, unexplained high CPU usage, often near 100% continuously
• Unusual process names, frequently with random or disguised names mimicking system processes
• Unfamiliar outbound network connections, often to mining pool servers
• Server running noticeably slower than usual for no apparent application-level reason
• Increased hosting/electricity costs on providers billing by CPU usage

Step 1 — Identify the Suspicious Process

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Look for a process consuming very high, sustained CPU with an unfamiliar or suspicious name.

Step 2 — Investigate the Process Details

ps -p PID -o pid,ppid,cmd,%cpu,user
sudo ls -la /proc/PID/exe

Check the actual binary location and parent process — cryptominers often run from unusual locations like /tmp or hidden directories.

Step 3 — Check Network Connections from the Process

sudo lsof -p PID | grep -i TCP

Connections to unfamiliar IPs, especially on non-standard ports, are a strong signal of a mining pool connection.

Step 4 — Do Not Simply Kill the Process and Move On

Killing the process alone doesn't address how it got there — cryptomining malware frequently includes persistence mechanisms (cron jobs, systemd services, SSH key additions) that will simply restart it, or worse, is just one visible symptom of a broader compromise.

Step 5 — Check for Persistence Mechanisms

crontab -l
sudo cat /etc/crontab
ls /etc/cron.d/
systemctl list-units --type=service | grep -v "^UNIT"

Look for unfamiliar entries added recently.

Step 6 — Check for Unauthorized SSH Keys

cat ~/.ssh/authorized_keys
sudo cat /root/.ssh/authorized_keys

Compare against keys you actually recognize.

Step 7 — Check for New/Unfamiliar User Accounts

cat /etc/passwd

Step 8 — Determine the Entry Point

Common entry points for cryptomining malware:

• Weak or reused SSH credentials
• An unpatched vulnerability in a web application or exposed service
• An exposed, unauthenticated Docker daemon or database
• A vulnerable dependency (see How to Audit and Secure Your Application's Dependencies)

Step 9 — Follow Full Incident Response

Given the difficulty of confirming complete removal on an actively compromised system, the recommended approach is a full rebuild — see How to Recover from Ransomware or a Compromised VPS for the complete process, including rotating all credentials.

Step 10 — Verify the Fix Prevents Recurrence

Address the specific entry point identified in Step 8 before returning to production — follow VPS Security Checklist for Beginners as a baseline, plus any specific fix for the identified vulnerability.

Prevention Going Forward

• SSH key authentication only, strong hardening — see SSH Hardening: Change the Port, Disable Root Login & Use SSH Keys
• Regular security updates and dependency audits
• Monitoring for sustained unusual CPU usage — see How to Set Up Effective Server Alerting
• Never expose Docker daemon or databases directly to the public internet

Continue Reading

• How to Recover from Ransomware or a Compromised VPS
• How to Diagnose and Fix High CPU Usage on a VPS
• How to Detect and Remove Rootkits on a Linux VPS

Browse more articles in Advanced Security & Compliance.