PDF malware analysis — malicious · c51d44f0529e7ddc

MALICIOUS

PDF

174.0 KB Created: 2009-08-17 21:45:05 +08:00

MD5: 074797d53af11475abd8d76091e24215 SHA-1: 8396e65fa7bf08f7dfc0a879154ec051a0ac07ba SHA-256: c51d44f0529e7ddce16c36969143509fb7a284a1fb9a61a98fc0aaf8081cf527

148 Risk Score

Malware Insights

MITRE ATT&CK

T1059.001 PowerShell

The PDF contains embedded JavaScript, indicated by multiple heuristic firings including PDF_JAVASCRIPT, PDF_JS, and PDF_GENERIC_STAGE_RECOVERY. The ML classifier also flagged this PDF as malicious. The JavaScript appears to be obfuscated and attempts to recover an exploit stage. The primary intent seems to be downloading and executing a second-stage payload from the embedded resources, which are identified as JavaScript files and a decoded binary stream. Due to the obfuscation and incomplete ClamAV scan, the exact payload and execution method are not fully discernible, leading to a moderate confidence score.

Machine Learning

Nyx PDF Classifier malicious score 0.8523

Heuristics 10

eval() call high PDF_EVAL

eval() found — commonly used for obfuscated exploit execution (matched inside decoded stream)
Generic recovered JavaScript exploit stage high PDF_GENERIC_STAGE_RECOVERY

Bounded static stage recovery exposed hidden JavaScript through generic transforms such as null-byte collapse, percent decoding, marker replacement, arithmetic character codes, fromCharCode, numeric arrays, or hex literals. This rule is emitted only when the recovered stage contains exploit-like Acrobat JavaScript or shellcode markers.
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. (matched inside decoded stream)
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. (matched inside decoded stream)
Embedded file low PDF_EMBEDDED

PDF embeds a file attachment — could carry an executable or another weaponised document as a nested payload (matched inside decoded stream)
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. (matched inside decoded stream)
PDF differential parser failed info PDF_DIFFERENTIAL_PARSE_FAILED

The cross-check parser (pdfminer.six) failed on this file: PDF differential parser exited 1. Static heuristics still ran and any of their findings above are valid; only the differential cross-check signal is missing.
Suspicious extracted artifact info 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.
ClamAV scan did not complete on extracted artifact info CLAMAV_SCAN_INCOMPLETE

ClamAV did not complete on 3 carved artifact(s); EXTRACTED_FILE_CLAMAV may be missing for this run. The result is not cached so a later submission will retry the scan.
Embedded URL info EMBEDDED_URL

One or more URLs were extracted from the document. The URL itself is not a detection — see the per-URL labels for which channel (macro, JS, link annotation, document body, ...) reached each URL.
URL http://www.w3.org/1999/02/22-rdf-syntax-ns#
- http://ns.adobe.com/xap/1.0/
- http://purl.org/dc/elements/1.1/
- http://ns.adobe.com/xap/1.0/mm/
- http://ns.adobe.com/pdf/1.3/

Extracted artifacts 3

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`stream_004_off00000674.js` `5ff92f5502ee1cae01cbaad9a28aea7c3f90a417f1ea57fecc297ac6c7f18e5c`	decompressed-pdf-stream	PDF FlateDecoded stream at offset 0x674	3658 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 2 eval/decoder/string-building token(s).
`generic_stage_recovery_000.js` `9190eaafc6d850279c9d2d4a66543b52784ab9a89f0d74826ff910ca7d97a6e9`	deobfuscated-js	generic stage recovery percent-decode from decompressed stream at 0x674 at offset 0x674	3476 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 2 eval/decoder/string-building token(s).
`objstm_0026_00.bin` `e64642f7d054b6fe06eb3d71d841961a918a29f4bb39c60d85d7a97b6273524b`	pdf-objstm-decoded	PDF /ObjStm 26 0 obj (inflated)	306 bytes

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