PDF malware analysis — malicious · 31cba21d0b6ce05c

MALICIOUS

PDF

12.0 KB Created: 2011-01-31 16:32:23 +03:00 Authoring application: rz_9_kn (via c2e8b74def)

MD5: b960b6a7d3c06fca727e049bc7adfabf SHA-1: ee76c93ed44071a5147a14fb92b2e028c6161b0f SHA-256: 31cba21d0b6ce05cea3ef555467a554e5d9f84fd9314c8cc502f434fce3fd9b6

104 Risk Score

Malware Insights

MITRE ATT&CK

T1059.001 PowerShell

The PDF file contains embedded JavaScript, indicated by multiple heuristic firings including 'PDF_JAVASCRIPT', 'PDF_JS', and 'PDF_EVAL'. The 'eval()' call and 'String.fromCharCode' usage within the JavaScript streams suggest code obfuscation and dynamic execution. The ML classifier also flagged this PDF as malicious with high confidence. The primary attack pattern involves leveraging these JavaScript features to likely download and execute a second-stage payload.

Machine Learning

Nyx PDF Classifier malicious score 0.9997

Heuristics 6

eval() call high PDF_EVAL

eval() found — commonly used for obfuscated exploit execution (matched inside decoded stream)
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)
Optional Content Group with action trigger low PDF_OPTIONAL_CONTENT

Optional Content Group (layer) co-occurs with an action trigger — content can be selectively hidden from viewers or scanners while the action still fires on open
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_obj0011_000.js` `258559416ab0e894f201fb73fd676b770beffd71b0d07d51570035850491d6ed`	pdf-javascript-stream	PDF /JS object 11 at offset 0x2375	2460 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 2 eval/decoder/string-building token(s).
`javascript_obj0013_001.js` `b49be252cac6e937bc06044e9360ae806935f87a20a29a9a03512a6843f28784`	pdf-javascript-stream	PDF /JS object 13 at offset 0x27C0	1101 bytes
`javascript_obj0015_002.js` `c5b017dde8ddeec16da8ce547f2ed8da66b241f0b2a714900cb6fc000974fc43`	pdf-javascript-stream	PDF /JS object 15 at offset 0x2A3F	308 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 1 eval/decoder/string-building token(s).

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