Absurd 12-Step Malware Dropper Spotted in Malicious npm Packages

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A sophisticated malware dropper was discovered in malicious npm packages, employing steganography, Unicode obfuscation, and a multi-stage payload delivery system. This supply chain attack highlights the growing complexity of threats targeting open-source repositories.

Read the full article: https://lnkd.in/egxCY9Bt

You Should Know:

1. Steganography in Malware

Attackers hid malicious code inside seemingly harmless image files using steganography. To detect such files in Linux: 

binwalk -e suspicious_image.png 
strings suspicious_image.png | grep -i "eval|base64|http"

2. Unicode Obfuscation

The malware used a “dizzying wall of Unicode characters” to evade detection. To analyze obfuscated JavaScript: 

node --print-ast malicious_script.js

Or use CyberChef (https://gchq.github.io/CyberChef/) to decode Unicode.

3. Multi-Stage Payload Execution

The attack involved 12 steps, including:

  • Dependency Confusion: Fake npm packages mimicking legitimate ones.
  • Living-off-the-Land (LotL): Using legitimate tools like `curl` or `certutil` for payload retrieval. 
    Monitor suspicious network connections 
sudo netstat -tulnp | grep -E "curl|wget|certutil"

4. Detecting Malicious npm Packages

 Check package integrity 
npm audit 
npm ls --depth=0 
 Scan for known malware 
npx better-npm-audit audit

5. Windows Defender for Supply Chain Attacks

 Scan for hidden payloads 
Get-MpThreatDetection | Where-Object { $_.InitialDetectionTime -gt (Get-Date).AddDays(-1) }

6. YARA Rule for Detection

rule npm_malware_dropper { 
meta: 
description = "Detects npm malware using steganography & Unicode obfuscation" 
strings: 
$unicode_obf = /\u[0-9a-fA-F]{4}/ wide 
$steg_keywords = "fromCharCode|eval|atob" nocase 
condition: 
any of them 
}

7. Preventing Supply Chain Attacks

  • Use Sigstore for package signing verification: 
    cosign verify ghcr.io/your-repo/package@sha256:abc123
  • Enforce SBOM (Software Bill of Materials): 
    syft scan dir:./ --output spdx-json > sbom.json

What Undercode Say:

Supply chain attacks are evolving with advanced evasion techniques. Security teams must:
– Monitor npm/pip dependencies for suspicious updates.
– Analyze Unicode-heavy scripts using automated tools.
– Restrict outbound network calls from build systems.
– Use runtime protection (Falco, AppArmor) to detect malicious behavior.

 Linux hardening against supply chain attacks 
sudo apt install apparmor-utils 
sudo aa-enforce /etc/apparmor.d/bin.npm

Prediction:

Attackers will increasingly abuse AI-generated code in open-source packages to bypass traditional detection. Expect more “polyglot payloads” (files that are valid in multiple formats, e.g., PDF + JavaScript).

Expected Output:

npm audit 
binwalk -e payload.png 
node --print-ast obfuscated.js

IT/Security Reporter URL:

Reported By: Wysopal Absurd – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅

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