PDF malware analysis — malicious · 8c6588abdbb4aef2

MALICIOUS

PDF

108.8 KB Authoring application: PyPDF2

MD5: 62fd3986c0aa8e47ff1a275c42b4344d SHA-1: 9b037798a86fdcfdd13e28b4f0788d52e6144571 SHA-256: 8c6588abdbb4aef2d9dc522aee1587013583a71a6348988e12d9866d874e492f

396 Risk Score

Malware Insights

MITRE ATT&CK

T1059.001 PowerShell T1204.002 Malicious File T1566.002 Spearphishing Attachment

The file is a PDF containing obfuscated JavaScript, flagged by multiple heuristics as a JavaScript exploit cluster and an ActiveX downloader. ClamAV detections (Win.Downloader.Nemucod-6769668-0) on both the original file and an extracted artifact strongly indicate its malicious nature. The JavaScript is designed to download and execute a second-stage payload, consistent with the Nemucod downloader family's behavior.

Machine Learning

Nyx PDF Classifier malicious score 0.9998

Heuristics 11

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.
PDF paints image(s) but contains no text operators info PDF_IMAGE_ONLY_LURE

PDF has 2 image XObject(s) and the content stream contains no text-emitting operators (BT/ET, Tj, TJ, ', ") in either raw bytes or decompressed streams — this is the screenshot-as-PDF pattern used to bypass text-based scanners and to deliver instructions purely through rendered pixels. It is informational unless paired with invisible links or risky URI context.

Extracted artifacts 4

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`javascript_obj0009_000.js` `57347ca68aeee7c54520aabbb4d13654096a1428d713e6997ef237fb2a49e147`	pdf-javascript-stream	PDF /JS object 9 at offset 0x56E	13087 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_obj0009_001.js` `ea5d63a09334abf273a446805c744a9202107756736c60bde633fb6c7db1110f`	pdf-javascript-stream	PDF /JS object 9 at offset 0x56E	988 bytes
`acroform_b64_00.js` `0e752bdefadc04c6f26519893dcdd99931d4e21349f5a0ad393239c84ece1678`	deobfuscated-js	PDF AcroForm base64 (raw) at offset 0x16D4	5301 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_00004a64.bin` `914cc37703c42e08fe9a6bf2e6b1d83a4ec4e20b92fd7c9699dffd47bffd3938`	pdf-embedded-script	PDF decompressed stream script payload at offset 0x4A64	111388 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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