Malicious PDF — malware analysis report

Static analysis result for SHA-256 671d026e39e98a4f…

MALICIOUS

PDF

592.9 KB
MD5: 59186f50b2313d83ac6a790d13d09bbb SHA-1: 573e6b7e86f7c036d433dcdbc736587a3d8ddd23 SHA-256: 671d026e39e98a4fc89e8971e8dd5a854a32e497673735b8d82c1bc58da4a6f6
180 Risk Score

Malware Insights

MITRE ATT&CK
T1059.007 JavaScript T1203 Exploitation for Client Execution T1566.001 Spearphishing Attachment

This PDF file contains embedded JavaScript that is heavily obfuscated using string concatenation and `fromCharCode`. The JavaScript is flagged as an exploit cluster and is likely responsible for downloading and executing a secondary payload. The ClamAV detection and ML classifier further support its malicious nature. No specific family could be identified due to the obfuscation and lack of distinct indicators.

Machine Learning

  • Nyx PDF Classifier malicious score 0.9998

Heuristics 8

  • PDF JavaScript exploit cluster critical PDF_JS_EXPLOIT_CLUSTER
    PDF combines an executable JavaScript/action surface with exploit staging indicators such as eval/unescape/fromCharCode, XFA script content, or a related CVE pattern. Benign form JavaScript remains low-severity, but this correlated cluster is high-confidence malicious behavior.
  • ClamAV: Pdf.Exploit.Agent-23176 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Pdf.Exploit.Agent-23176
  • JavaScript action low PDF_JAVASCRIPT
    PDF contains a /JavaScript action. Generic JavaScript is common in benign forms; specific dangerous APIs are scored by separate rules.
  • Embedded JS stream low PDF_JS
    PDF references a /JS stream. Generic JavaScript is common in benign forms; specific dangerous APIs are scored by separate rules.
  • String.fromCharCode low PDF_FROMCHARCODE
    String.fromCharCode found — used to construct payload strings dynamically. Common in benign JavaScript libraries for codepoint manipulation, so this alone is informational; weaponised use is also caught by the dedicated fromCharCode-stage and exploit-shape rules. (matched inside decoded stream)
  • PDF differential parser failed info PDF_DIFFERENTIAL_PARSE_FAILED
    The cross-check parser (pdfminer.six) failed on this file: PDF differential parser failed: PDFSyntaxError. Static heuristics still ran and any of their findings above are valid; only the differential cross-check signal is missing.
  • Suspicious extracted artifact info EXTRACTED_FILE_STATIC_TRIAGE
    One or more files extracted from inside this sample matched static suspicious-content checks such as script obfuscation, encoded payload blobs, packed data, or execution/download terms.
  • Embedded URL info EMBEDDED_URL
    One or more URLs were extracted from the document. The URL itself is not a detection — see the per-URL labels for which channel (macro, JS, link annotation, document body, ...) reached each URL.
    URL http://reporter.mozilla.org/privacy/
    • http://reporter.mozilla.org/service/
    • http://getfirefox.com/releases/
    • http://en-US.start.mozilla.com/firefox?client=firefox-a&rls=org.mozilla:en-US:official
    • http://www.answers.com/main/ntquery
    • https://addons.mozilla.org/searchplugins/updates/answers.src
    • https://addons.mozilla.org/searchplugins/updates/answers.png
    • http://www.google.com/search
    • https://addons.mozilla.org/searchplugins/updates/google.src
    • https://addons.mozilla.org/searchplugins/updates/google.gif
    • http://www.w3.org/1999/02/22-rdf-syntax-ns#
    • http://home.netscape.com/NC-rdf#
    • http://www.mozilla.org/unix/customizing.html#prefs

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
javascript_obj1054_000.js
b77987ebbbc9d5466f77aac85bec69019c472ab6bf367e31245a125942ad9996		 pdf-javascript-stream PDF /JS object 1054 at offset 0x29 84010 bytes
Detection
ClamAV: No threats found
Obfuscation or payload: likely
Carved artifact contains 1 eval/decoder/string-building token(s). Carved artifact contains 2 long base64-like blob(s).

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