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analyzing-malicious-pdf-with-peepdf

analyzing-malicious-pdf-with-peepdf

github.com/mukul975Security35.2k389 installsUpdated 8w ago
Repository

About analyzing-malicious-pdf-with-peepdf

A skill guide for security analysts examining suspicious PDFs with peepdf and supporting tools. It covers locating malicious objects, extracting content, analyzing JavaScript, and compiling IOCs.

Key features

  1. 01Scan for suspicious PDF keywords
  2. 02Inspect PDF objects interactively
  3. 03Extract and decode streams
  4. 04Analyze embedded JavaScript
  5. 05Compile threat IOCs

Use cases

  1. 01Triage PDF attachments from phishing emails
  2. 02Analyze PDF exploit documents
  3. 03Extract scripts or files from PDFs

Install

Copy the command and run it in a terminal.

$npx skills add https://github.com/mukul975/anthropic-cybersecurity-skills --skill analyzing-malicious-pdf-with-peepdf

After installing, type/analyzing-malicious-pdf-with-peepdfin Claude Code to confirm it loaded.

Bundled files

References and scripts installed along with SKILL.md.

LICENSE
references/
api-reference.md
scripts/
agent.py

Details

From the project README

Analyzing Malicious PDF with peepdf

When to Use

  • When triaging suspicious PDF attachments from phishing emails
  • During malware analysis of PDF-based exploit documents
  • When extracting embedded JavaScript, shellcode, or executables from PDFs
  • For forensic examination of weaponized document artifacts
  • When building detection signatures for PDF-based threats

Prerequisites

  • Python 3.8+ with peepdf-3 installed (pip install peepdf-3)
  • pdfid.py and pdf-parser.py from Didier Stevens suite
  • Isolated analysis environment (VM or sandbox)
  • Optional: PyV8 for JavaScript emulation within peepdf
  • Optional: Pylibemu for shellcode analysis

Workflow

  1. Triage with pdfid: Scan PDF for suspicious keywords (/JS, /JavaScript, /OpenAction, /Launch, /EmbeddedFile).
  2. Interactive Analysis: Open PDF in peepdf interactive mode to explore object structure.
  3. Identify Suspicious Objects: Locate objects containing JavaScript, streams, or encoded data.
  4. Extract Content: Dump suspicious streams and decode filters (FlateDecode, ASCIIHexDecode).
  5. Deobfuscate JavaScript: Analyze extracted JS for shellcode, heap sprays, or exploit code.
  6. Check VirusTotal: Use peepdf vtcheck to cross-reference file hash with AV detections.
  7. Generate IOCs: Extract URLs, domains, hashes, and shellcode signatures.

Key Concepts

ConceptDescription
/OpenActionAutomatic action executed when PDF is opened
/JavaScript /JSEmbedded JavaScript code in PDF objects
/LaunchAction that launches external applications
/EmbeddedFileFile embedded within the PDF structure
FlateDecodezlib compression filter used to hide content
Object StreamsPDF objects stored in compressed streams

Tools & Systems

ToolPurpose
peepdf / peepdf-3Interactive PDF analysis with JS emulation
pdfid.pyQuick triage scanning for suspicious keywords
pdf-parser.pyDeep object-level PDF parsing
VirusTotalHash lookup and AV detection cross-reference
CyberChefDecode and transform extracted payloads

Output Format

Analysis Report: PDF-MAL-[DATE]-[SEQ]
File: [filename.pdf]
SHA-256: [hash]
Suspicious Keywords: [/JS, /OpenAction, etc.]
Objects with JavaScript: [Object IDs]
Extracted URLs: [List]
Shellcode Detected: [Yes/No]
Embedded Files: [Count and types]
VirusTotal Detections: [X/Y engines]
Risk Level: [Critical/High/Medium/Low]

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