PDF malware analysis — malicious · 4deb3768bd06e9a2

MALICIOUS

PDF

72.1 KB Authoring application: PyPDF2

MD5: 8ab3dc994427cf651d6b5a43a66e9015 SHA-1: 7b1b279f8f524315be0b80bad2a18fd392a0edbf SHA-256: 4deb3768bd06e9a2b348937dc1a9e6d89db57df6f6b1d8b04a4d6681b1418e50

394 Risk Score

Malware Insights

MITRE ATT&CK

T1059.001 PowerShell T1204.002 Malicious File

The PDF contains embedded JavaScript that utilizes eval() and String.fromCharCode() for obfuscation, a common technique for downloading and executing further payloads. The ClamAV detection of 'Win.Downloader.Nemucod-6769668-0' on both the initial PDF and an extracted artifact strongly suggests this family of downloader. The script's complexity and use of obfuscation indicate a deliberate attempt to conceal its malicious actions, likely to download and run a second-stage payload.

Machine Learning

Nyx PDF Classifier malicious score 0.9974

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_obj0008_000.js` `a89957867c89d41b9a2af1523fd0a1b470604b83985dba323950b624ab51bcb9`	pdf-javascript-stream	PDF /JS object 8 at offset 0x34F	13156 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_obj0008_001.js` `ea5d63a09334abf273a446805c744a9202107756736c60bde633fb6c7db1110f`	pdf-javascript-stream	PDF /JS object 8 at offset 0x34F	988 bytes
`acroform_b64_00.js` `0e752bdefadc04c6f26519893dcdd99931d4e21349f5a0ad393239c84ece1678`	deobfuscated-js	PDF AcroForm base64 (raw) at offset 0x14F9	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_000048d2.bin` `84dd1e40b82f71d90c6e84837082d8e6f2b6b54dd35abd0dff61c29851c9439d`	pdf-embedded-script	PDF decompressed stream script payload at offset 0x48D2	73795 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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