PDF malware analysis — malicious · 5dc75171f8ffe096

MALICIOUS

PDF

16.5 KB

MD5: 60add14f23a24abda6c825ed32af3ab1 SHA-1: 7467532a68f45318054bb9d5cbb3f52bd17a6520 SHA-256: 5dc75171f8ffe09671035f0f5765a6f639af6d76c11585dc77019252ed448a28

136 Risk Score

Malware Insights

MITRE ATT&CK

T1059.007 JavaScript T1566.001 Spearphishing Attachment

This PDF file contains obfuscated JavaScript designed to act as a dropper. The script attempts to evade analysis by checking the number of plugins and uses a split-literal technique to reconstruct a payload from annotation subjects. It then executes this payload, likely to download and run a second-stage malicious file. The ML classifier strongly indicates maliciousness.

Machine Learning

Nyx PDF Classifier malicious score 1.0000

Heuristics 6

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, numeric-array minus-key decoders, alphabet-index arrays, /Producer half-difference metadata arrays, hex literals, marker-stripped Base64 literals, custom 6-bit XOR table decoders, or repeated-marker hex carriers. This rule is emitted only when the recovered stage contains exploit-like Acrobat JavaScript or shellcode markers.
Obfuscated multi-stage PDF JavaScript dropper high PDF_JS_OBFUSCATED_DROPPER

PDF JavaScript shows 3 independent signals of exploit-kit-style multi-stage obfuscation: annot_subject_stage, hex_dashed_payload, 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.
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 5

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`javascript_obj0005_000.js` `a2765ef4bc176af71164210608f93ccd0cfd1d5803648c48f5d630ef03f5faa9`	pdf-javascript-stream	PDF /JS object 5 at offset 0x148	749 bytes
`generic_stage_recovery_000.js` `2cddb2bc6087d7e401900b317c670724f2f13cb3e511de2bcf362f30cd1285e7`	deobfuscated-js	generic stage recovery split-literal-normalize from JavaScript object 5 at offset 0x148	737 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` `a2a7b367384d36763cec4c286fd0f9b5df53ec42a0c26597869325add0a43c68`	deobfuscated-js	repeated-marker hex decoded JavaScript at offset 0x1C1F	13057 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).
`legacy_pdfkit_stage_001.js` `5798755f9a1532eda80962679123febe3b0b4f07cba2c7a34c5b7e140c061d1e`	deobfuscated-js	nested inline base-23 callee-key decoded JavaScript at offset 0x1C1F	5186 bytes
`deobfuscated.js` `2b7cd4a1ae887c5556aa2681b9926ff9924d6ed1c0012680727634adc73178c3`	deobfuscated-js	PDF JavaScript deobfuscation pass	65410 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 1 long base64-like blob(s).

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