Win.Downloader.Nemucod-6769668-0 PDF malware analysis — malicious · 560f56054db1ee0f

MALICIOUS

PDF

200.1 KB Authoring application: PyPDF2

MD5: 6828abf37aa76c491d4118c07ed55f7c SHA-1: 00600e42edb55daa61aeffb0efe456b6bdff13d3 SHA-256: 560f56054db1ee0fea994c398e6681e361e1a68204e9bbf7d4746e36cc80594e

394 Risk Score

Malware Insights

Win.Downloader.Nemucod-6769668-0 · confidence 95%

MITRE ATT&CK

T1059.001 PowerShell T1204.002 Malicious File T1071.001 Web Protocols

This PDF file contains embedded JavaScript that is heavily obfuscated. Heuristics indicate it functions as an ActiveX downloader, likely to retrieve and execute a second-stage payload. The ClamAV detection of 'Win.Downloader.Nemucod-6769668-0' strongly suggests this family and its typical downloader behavior. The extracted JavaScript files and the PDF JavaScript exploit cluster further support this assessment.

Machine Learning

Nyx PDF Classifier malicious score 0.9870

Heuristics 10

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: Win.Downloader.Nemucod-6769668-0 critical CLAMAV_DETECTION

ClamAV detected this file as malware: Win.Downloader.Nemucod-6769668-0
ClamAV detection on extracted artifact critical EXTRACTED_FILE_CLAMAV

ClamAV flagged at least one file extracted from inside this sample. Even when the wrapping document carries no AV detection of its own, a hit on the carved artifact is a strong indicator the sample is a delivery vehicle.
eval() call high PDF_EVAL

eval() found — commonly used for obfuscated exploit execution
Embedded script payload in PDF stream high PDF_EMBEDDED_SCRIPT_PAYLOAD

PDF stream bytes contain script execution markers such as ActiveXObject/CreateObject, WScript.Shell, PowerShell, or shell-exec primitives. This is stronger than ordinary PDF JavaScript because it indicates a staged external script payload hidden in stream bytes.
PDF JavaScript ActiveX downloader high PDF_JS_ACTIVEX_DOWNLOADER

Decoded PDF JavaScript instantiates Windows ActiveX/COM objects to download a payload over HTTP, write it through ADODB.Stream, and execute it through WScript.Shell/rundll32-style process launch. This is commodity downloader behavior rather than a specific Acrobat CVE trigger.
Suspicious extracted artifact high 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.
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.

Extracted artifacts 4

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`javascript_obj0006_000.js` `2c3a671d99b1d877d29f9b14266ee60bbcc63e7bad989afb1f5a0333ec064209`	pdf-javascript-stream	PDF /JS object 6 at offset 0x3C9	13203 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 4 eval/decoder/string-building token(s). Carved artifact contains 2 long base64-like blob(s).
`javascript_obj0006_001.js` `b6f9509a2533b9f1a1699ab168cfed2adfd145a178d1a4ce8c6a5bbaebd85483`	pdf-javascript-stream	PDF /JS object 6 at offset 0x3C9	7780 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 2 long base64-like blob(s).
`acroform_b64_00.js` `a7132ec71d3510814e863e1380172dfc7fbf035bd25b7ba6ab73f2bfa2adf99c`	deobfuscated-js	PDF AcroForm base64 (raw) at offset 0x64F	5327 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 2 shell/COM execution token(s). Carved artifact contains 1 eval/decoder/string-building token(s).
`embedded_pdf_script_000048f3.bin` `7c4930ec2275875366a1be414bab02fbdac3824ee61f9ebd1935f23859ed8948`	pdf-embedded-script	PDF decompressed stream script payload at offset 0x48F3	204887 bytes
Detection ClamAV: Win.Downloader.Nemucod-6769668-0 Obfuscation or payload: likely Carved artifact contains 2 shell/COM execution token(s). Carved artifact contains 12 eval/decoder/string-building token(s). Carved artifact contains 2 long base64-like blob(s).

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