PDF malware analysis — malicious · 6675401d9e522e25

MALICIOUS

PDF

16.1 KB

MD5: fc1792b24aa8f43b502abc2955cfe2eb SHA-1: 9915326db9ee5c5063756d384f993ca497a8dc53 SHA-256: 6675401d9e522e25b218b3bc87a8b95fa5b467159fda604408fa37caf712c198

196 Risk Score

Malware Insights

MITRE ATT&CK

T1059.007 JavaScript T1566.001 Spearphishing Attachment

This PDF file contains heavily obfuscated JavaScript, identified as a multi-stage dropper. The script attempts to evade analysis by checking the number of plugins and uses a split-literal-normalize technique to reconstruct a payload from annotation subjects. The primary function appears to be downloading and executing a second-stage payload, as indicated by the 'Obfuscated multi-stage PDF JavaScript dropper' heuristic and ClamAV detection.

Machine Learning

Nyx PDF Classifier malicious score 1.0000

Heuristics 7

ClamAV: Pdf.Dropper.Agent-7268172-0 critical CLAMAV_DETECTION

ClamAV detected this file as malware: Pdf.Dropper.Agent-7268172-0
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` `a3319192cac6d4dc4eeb6af2d736b0ffec979b23116a003bc7c23382761c32a5`	pdf-javascript-stream	PDF /JS object 5 at offset 0x148	733 bytes
`generic_stage_recovery_000.js` `d0d9b30997e09d7380aa1f50db3a2ef0c80cafe011beab0224533da2964e68f5`	deobfuscated-js	generic stage recovery split-literal-normalize from JavaScript object 5 at offset 0x148	717 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` `830da7fa7e50f9c1aaa46443ecf8a3065ec60a712bb89e9807463b3a3c8ad203`	deobfuscated-js	repeated-marker hex decoded JavaScript at offset 0x1B73	12668 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` `b554c3ac2cb0b3e6376521ecf6215e449fdb427cdda8521f41e5c58dd06884bd`	deobfuscated-js	nested inline base-23 callee-key decoded JavaScript at offset 0x1B73	5062 bytes
`deobfuscated.js` `dcdedeb8b7b5ba48481ab7cd44d432c89f2b557cc7fb88885bc352571e0e6c6f`	deobfuscated-js	PDF JavaScript deobfuscation pass	110293 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 1 long base64-like blob(s).

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