PDF malware analysis — malicious · 4baeb6743364a6ed

MALICIOUS

PDF

40.6 KB Authoring application: PyPDF2

MD5: 74f74ef2fa0bdfa3115c149ba22cb528 SHA-1: 94c6aaff4288af71e37057143cc7589e0f2e6d5c SHA-256: 4baeb6743364a6ed942ed51fb989c396a6aebc5cbb71222e8c9093a4dcb4f578

276 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, indicative of obfuscation and exploit execution. The 'PDF_JS_ACTIVEX_DOWNLOADER' heuristic strongly suggests the script's purpose is to download a second-stage payload. The reconstructed string 'Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.0)' appears to be a User-Agent string, and 'Windows Script Host' is also present, suggesting the execution of downloaded scripts. The presence of a 'downloader' heuristic and the ML classifier's high confidence further support this assessment.

Machine Learning

Nyx PDF Classifier malicious score 1.0000

Heuristics 9

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.
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 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 4

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`javascript_obj0004_000.js` `a78bad20a461398905fa715ea4460c7e7b5f8b5c0fa5227f6c38551c8f2a825c`	pdf-javascript-stream	PDF /JS object 4 at offset 0x13F	12394 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_obj0004_001.js` `2f2687168a224cb8f1d1ce7c5072d0f5507ed89b9aa66edf29f8c123eaf80286`	pdf-javascript-stream	PDF /JS object 4 at offset 0x13F	607 bytes
`acroform_b64_00.js` `0e752bdefadc04c6f26519893dcdd99931d4e21349f5a0ad393239c84ece1678`	deobfuscated-js	PDF AcroForm base64 (raw) at offset 0x101D	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_00004256.bin` `13da987d885b0133657a35dba13f2fa808779eb7d9948191b910cfd5ef5117d6`	pdf-embedded-script	PDF decompressed stream script payload at offset 0x4256	41609 bytes
Detection ClamAV: No threats found 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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