Malicious PDF — malware analysis report

Static analysis result for SHA-256 c81ea7b4af1819ed…

MALICIOUS

PDF

71.3 KB Created: 2021-09-20 19:19:22 +03:00 Authoring application: wkhtmltopdf 0.12.5 (via Qt 5.11.3)
MD5: c4c8923491c2be0b586de6bb819d97ff SHA-1: 066123735135d6a15d096743832419650b2f9261 SHA-256: c81ea7b4af1819ed132b4cc2c707a5228bb1c3f6b7b4a10a291187a6634fef3f
156 Risk Score

Malware Insights

MITRE ATT&CK
T1566.001 Spearphishing Attachment T1203 Exploitation for Client Execution

This PDF was flagged by multiple heuristics and a machine learning classifier as malicious, with ClamAV identifying it as a phishing trojan. It contains numerous links pointing to compromised WordPress upload storage and other disposable hosting, suggesting a link farm designed to redirect users to malicious content. The document body is heavily obfuscated and appears to be generated by wkhtmltopdf, further obscuring its malicious intent.

Machine Learning

  • Nyx PDF Classifier malicious score 0.9994

Heuristics 6

  • ClamAV: Pdf.Phishing.Trojan-d2528dad23a95d95-d2528dad23a95d95-10044376-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Pdf.Phishing.Trojan-d2528dad23a95d95-d2528dad23a95d95-10044376-0
  • PDF link farm points to compromised-WordPress upload storage medium PDF_COMPROMISED_CMS_UPLOAD_LINK_FARM
    PDF contains multiple clickable links, across many distinct hosts, whose targets are random-slug files parked in the upload directories of vulnerable WordPress form plugins (FormCraft, Super Forms). This is the hallmark of the 'free document/template' SEO phishing PDF family, which ranks for search queries and routes users into payload/redirect chains hosted on compromised sites. The PDF itself carries no exploit — the risk is the linked destinations.
  • Small PDF is a non-clustered link farm on disposable hosting medium PDF_SEO_DISPOSABLE_LINK_FARM
    Small PDF contains many clickable external PDF links spread thin across many distinct hosts (no single dominant host), corroborated by a utm_term SEO-redirector link and/or links parked on free/disposable content hosts. This is the 'free document/template' SEO phishing PDF family, which ranks for search queries and routes users into payload/redirect chains, rather than a normal document citation pattern. The PDF itself carries no exploit — the risk is the linked destinations.
  • External URI info PDF_URI
    PDF contains an external URL action
  • Object number defined twice with different bodies info PDF_DUPLICATE_OBJ_BODY_INCREMENTAL
    The same indirect object (N G) is defined more than once with different body bytes. First-wins and last-wins readers will resolve different content, which is a parser-confusion shape used by targeted PDFs. Body-only differences are common in benign incremental updates, so severity is raised only when the duplicate carries active content.
  • Embedded URL info EMBEDDED_URL
    One or more URLs were extracted from the document. The URL itself is not a detection — see the per-URL labels for which channel (macro, JS, link annotation, document body, ...) reached each URL.
    URL https://destockbaby.com/ckfinder/userfiles/files/sikojadowasofigu.pdf
    • http://marjoleintje.nl/include/userfiles/dapabubakafibomiditide.pdf
    • http://flashdisplay.net/UploadFiles/FCKeditor/20210906022651.pdf
    • https://xn--78-6kce7dfhb9dwb.xn--p1ai/wp-content/plugins/super-forms/uploads/php/files/389249214bd4595d77aa8a643666b164/puwulamojaduvukevajif.pdf
    • http://manpukulivermore.com/uploads/files/dupexejitab.pdf
    • http://www.iuoelocal870.com/kaizen/ckfinder/userfiles/files/3912633375.pdf
    • http://thietbimaugiao.vn/Images_upload/files/64745236158.pdf
    • http://27derajat.com/assets/ckfinder/core/connector/php/uploads/files/78914988136.pdf
    • http://knipia.com/userfiles/file/veradomute.pdf
    • http://www.larucheapain.fr/ljk/file/jemowijikureji.pdf
    • https://carthink.org/wp-content/plugins/formcraft/file-upload/server/content/files/16132d01e49379---tizivafakepunatajimuvibu.pdf
    • http://cameragiaminh.com/upload/files/jaxefakeselezavafemabut.pdf
    • http://appli-veolia.net/ckfinder/userfiles/files/wolaza.pdf
    • http://for-rent-aalst.com/wp-content/plugins/formcraft/file-upload/server/content/files/161476157bd36e---jawivobemevorudulimedipo.pdf
    • https://yarsan.ru/wp-content/plugins/super-forms/uploads/php/files/37eac29e520cbc55d88ce28feec6fccf/99549069500.pdf
    • http://carlaschroyen.com/content_docs/49588429636.pdf
    • https://feedproxy.google.com/~r/1eyvgo/aqOO/~3/YTWXjIUwRh0/uplcv?utm_term=length+of+a+arc+formula
    • http://www.w3.org/1999/02/22-rdf-syntax-ns#
    • http://purl.org/dc/elements/1.1/
    • http://ns.adobe.com/pdf/1.3/
    • http://ns.adobe.com/xap/1.0/
    • http://ns.adobe.com/xap/1.0/mm/
    • http://ns.adobe.com/xap/1.0/rights/
    • http://dejavu.sourceforge.net
    • http://dejavu.sourceforge.net/wiki/index.php/License

Extracted artifacts 3

Files carved from inside the sample during analysis.

FilenameKindSourceSize
font_00_sfnt_off0000b2d7.bin
9d2294e344127da9ddc2b77d68b1576b6b78373885bc9da2859f180a98f2c1e1		 pdf-font-stream PDF embedded font (sfnt) at offset 0xB2D7 16792 bytes
font_01_sfnt_off0000caee.bin
3728b9ec67d6ed195d102ada41901c76de00c5c2bc81edf8e615a4184c1744b4		 pdf-font-stream PDF embedded font (sfnt) at offset 0xCAEE 10580 bytes
font_02_sfnt_off0000e2e8.bin
ab918a5625d2cea5a7c22a52503a6b0f6f3ca5662579b897fb517fcec24618f6		 pdf-font-stream PDF embedded font (sfnt) at offset 0xE2E8 17692 bytes

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