Malicious PDF — malware analysis report

Static analysis result for SHA-256 08c1111f21f1166e…

MALICIOUS

PDF

4.6 KB
MD5: 44909fa9fe57c0b0e442846942f2eb5f SHA-1: ac8e15e40ddf183d8af63e17c5e2a992182f4cb6 SHA-256: 08c1111f21f1166e966116c1a6f097a6727009e2054c0d42b99afd52ce5c01ae
86 Risk Score

Malware Insights

MITRE ATT&CK
T1059.007 JavaScript T1566.001 Spearphishing Attachment

The PDF contains embedded JavaScript that is obfuscated using string concatenation and XOR operations. The script reconstructs the string "charUv3A" + "CodeUKFI" + "KrpAtrpK" and uses it to call a method on the PDF object. It then reconstructs the string "uneVmHA" + "scape" and uses it to call a method on the PDF object. The script further reconstructs the string "Rj5getP" + "wYjageNjwY" + "7UithWoi7U" + "yXCrdyXC" and uses it to call a method on the PDF object. The script then reconstructs the string "Z45from" + "dU2Char2Ud" + "Code9aFO" and uses it to call a method on the PDF object. Finally, it reconstructs the string "xN5getPa" + "3vSgeNum" + "Words" and uses it to call a method on the PDF object. The script's primary function appears to be downloading and executing a second-stage payload, indicated by the "PDF_PAGE_WORD_XOR_EVAL_STAGER" heuristic. The presence of JavaScript and the stager heuristic strongly suggest a malicious intent, likely delivered via spearphishing.

Machine Learning

  • Nyx PDF Classifier malicious score 1.0000

Heuristics 3

  • Page-word XOR JavaScript eval stager high PDF_PAGE_WORD_XOR_EVAL_STAGER
    PDF JavaScript enumerates rendered page words with getPageNthWord/getPageNumWords, extracts encoded byte fragments, XOR-decodes the stage with char-code helpers, and evals the result. This is an old exploit-kit staging pattern and is not normal document JavaScript.
  • 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.

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
javascript_obj0011_000.js
725b7386f6e9caae9e03f9492eb7f26f190197c23637c755c72761214d6aafe9		 pdf-javascript-stream PDF /JS object 11 at offset 0xC9C 852 bytes

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