Nemucod PDF malware analysis — malicious · ab4890d9417c1999

MALICIOUS

PDF

65.8 KB Authoring application: PyPDF2

MD5: 22df17d7a14bae69e61823787b039554 SHA-1: 9f574e2c4fdfce346f11647559ed3c6f0efd89c8 SHA-256: ab4890d9417c1999b7268357e4d6dbe7655191904613592827494ed46c27ed3f

230 Risk Score

Malware Insights

Nemucod · confidence 95%

MITRE ATT&CK

T1059.001 PowerShell T1204.002 Malicious File

This PDF file was detected as malicious by ClamAV with the signature Txt.Downloader.Nemucod-6769573-0, indicating it belongs to the Nemucod family. Static analysis revealed embedded JavaScript streams and a high-confidence ML classifier prediction. The presence of PDF_JAVASCRIPT and PDF_EVAL heuristics, along with the ClamAV detection on an extracted artifact, strongly suggests that the embedded JavaScript is designed to download and execute a second-stage payload. The document body is heavily obfuscated and unreadable, providing no direct clues about the lure.

Machine Learning

Nyx PDF Classifier malicious score 0.9999

Heuristics 7

ClamAV: Txt.Downloader.Nemucod-6769573-0 critical CLAMAV_DETECTION

ClamAV detected this file as malware: Txt.Downloader.Nemucod-6769573-0
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
Suspicious extracted artifact medium 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.
PDF paints image(s) but contains no text operators info PDF_IMAGE_ONLY_LURE

PDF has 1 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 2

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`javascript_obj0004_000.js` `8d2a59b462c847fa81ef102c144be096b6b235cc7f092fbce854233a4f66bfed`	pdf-javascript-stream	PDF /JS object 4 at offset 0x134	17469 bytes
Detection ClamAV: Txt.Downloader.Nemucod-6769573-0 Obfuscation or payload: likely Carved artifact contains 48 eval/decoder/string-building token(s). Carved artifact contains 2 long hex-escaped blob(s).
`javascript_obj0004_001.js` `28e90f971086239457646ae79cab82de1ff8f19437baafa96c9c1a111715275e`	pdf-javascript-stream	PDF /JS object 4 at offset 0x134	736 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 1 eval/decoder/string-building token(s). Carved artifact contains 1 long hex-escaped blob(s).

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