PDF malware analysis — malicious · 8424bc9c555a6901

MALICIOUS

PDF

15.6 KB

MD5: 3449b2b633847330a8e402cd8dff07dc SHA-1: 2ce68e7d73b20a3e6affaf03519cb8410c78acdb SHA-256: 8424bc9c555a6901665716854c16dc23c06cf0f416e9f606adff4acf7f9e8750

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 length of app.plugIns and uses a split-literal string to construct a call to execute a payload. The payload is likely encoded within the annotation subject and reconstructed using string manipulation and a fromCharCode function.

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 4

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` `b2e3d9776669d111818dee4782c5dfc75f9f232794efa0314cf4810a97952b81`	deobfuscated-js	repeated-marker hex decoded JavaScript at offset 0x1A96	12463 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` `ca9ae0693ccec11a60b3d38db35629eabee5299dd3d946bec046ca9667c740e1`	deobfuscated-js	PDF JavaScript deobfuscation pass	63455 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 1 long base64-like blob(s).

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