PDF malware analysis — malicious · a4fad7e1cd874794

MALICIOUS

PDF

15.9 KB

MD5: df6c246a22530438eea2b46a46053eb7 SHA-1: dbb4214e6759ed25558fbde9eb189902b838a60a SHA-256: a4fad7e1cd8747944348c5b1419391ec88bd96de32ce81661aa7ec87dbf63cb1

166 Risk Score

Malware Insights

MITRE ATT&CK

T1059.001 PowerShell

The PDF contains heavily obfuscated JavaScript, flagged by multiple heuristics as a multi-stage dropper. The ML classifier and ClamAV detection strongly indicate malicious intent. The primary function appears to be downloading and executing a second-stage payload, as suggested by the 'PDF_JS_OBFUSCATED_DROPPER' heuristic. The specific ClamAV detection name 'Pdf.Exploit.Agent-35901' is included as a key indicator.

Machine Learning

Nyx PDF Classifier malicious score 1.0000

Heuristics 7

ClamAV: Pdf.Exploit.Agent-35901 critical CLAMAV_DETECTION

ClamAV detected this file as malware: Pdf.Exploit.Agent-35901
Obfuscated multi-stage PDF JavaScript dropper high PDF_JS_OBFUSCATED_DROPPER

PDF JavaScript shows 5 independent signals of exploit-kit-style multi-stage obfuscation: annot_subject_stage, hex_codec_loop, hex_dashed_payload, incremental_eval_build, repeated_pluginschk. This is strongly consistent with pre-2011 Adobe Reader PDF droppers — OpenAction JS reads encoded data from annotation subjects, decodes it through one or more hex / base-N loops, and invokes eval indirectly (method name built one character at a time). The actual CVE is hidden in the final decoded layer and is not visible via static analysis.
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. (matched inside decoded stream)
syncAnnotScan annotation-staging primitive low PDF_FOXIT_SYNCANNOTSCAN

PDF JavaScript calls syncAnnotScan() — a no-op annotation-enumeration primitive used by exploit-kit JavaScript to stage payload reads from annotation /Subject fields before eval(). Not a vulnerable sink itself; rarely seen in legitimate PDFs. (matched in decompressed stream)
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.

Extracted artifacts 3

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`javascript_obj0005_000.js` `4718a27c2224fc36bf24f8e8e04598f1ad78adce4401c7be2708318738a6983d`	pdf-javascript-stream	PDF /JS object 5 at offset 0x148	469 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 1 eval/decoder/string-building token(s).
`legacy_pdfkit_stage_000.js` `787c26d86c2812bc13839057c1aefffabf7e5bc5b2cf953e4fb4403f3ec3eb34`	deobfuscated-js	repeated-marker hex decoded JavaScript at offset 0x1B09	12058 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 base64-like blob(s).
`deobfuscated.js` `896d17f6a615d4ba03c261ce5669c4da87bfb12fe48a94f8a4420bfa39e21969`	deobfuscated-js	PDF JavaScript deobfuscation pass	110093 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 5 eval/decoder/string-building token(s). Carved artifact contains 2 long base64-like blob(s).

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