Malicious PDF — malware analysis report

Static analysis result for SHA-256 87ac78a96a221ebf…

MALICIOUS

PDF

203.2 KB Created: 2021-07-21 16:04:57 +09:00
MD5: 86ed2cc6a94b42f75e7746b8f432456b SHA-1: ea53fee4696867097647c5e56281574904f7f5eb SHA-256: 87ac78a96a221ebf61f90011cadb4e7a2ee9575758e6ffa20912464bf5d1f6ca
94 Risk Score

Malware Insights

MITRE ATT&CK
T1059.001 JavaScript/JScript T1204.002 Malicious File

The PDF file contains obfuscated JavaScript, triggered by a vulnerability in PDF viewers (CVE-2020-9715). The JavaScript is further deobfuscated, indicating a multi-stage approach. The primary goal appears to be the execution of this script, which is designed to download and execute additional malicious content.

Heuristics 6

  • dataObjects ESObject stale-cache trigger — CVE-2020-9715 critical CVE exact CVE_2020_9715
    PDF embeds a file and JavaScript follows the CVE-2020-9715 ESObject use-after-free trigger shape: access this.dataObjects[], clear the dataObjects entry, schedule app.setTimeOut(), then re-access the Data ESObject through toString().
  • 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.
  • Embedded file low PDF_EMBEDDED
    PDF embeds a file attachment — could carry an executable or another weaponised document as a nested payload
  • 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)
  • 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.
    URL http://www.w3.org/1999/02/22-rdf-syntax-ns#
    • http://ns.adobe.com/xap/1.0/
    • http://ns.adobe.com/xap/1.0/rights/
    • http://ns.adobe.com/pdf/1.3/
    • http://purl.org/dc/elements/1.1/
    • http://ns.adobe.com/xap/1.0/mm/

Extracted artifacts 2

Files carved from inside the sample during analysis.

FilenameKindSourceSize
javascript_obj0089_000.js
322a2481b996ba3f0a4676de8c2c9e6d44b1c7d6a69a1f8e2395866b53882a62		 pdf-javascript-stream PDF /JS object 89 at offset 0x1D5F2 341509 bytes
Detection
ClamAV: No threats found
Obfuscation or payload: likely
Carved artifact contains 6 eval/decoder/string-building token(s). Carved artifact contains 1 long base64-like blob(s).
custom_b64_stage_000.js
77f997ff3d7d7d5fbbd17c712cb7239c252894d726341c3d8593dec28d3bb638		 deobfuscated-js custom Base64 decoded JavaScript layer 1 (PDF /JS object 89) at offset 0x1DA9E 255159 bytes
Detection
ClamAV: No threats found
Obfuscation or payload: likely
Carved artifact contains 4 eval/decoder/string-building token(s).

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