Malicious PDF — malware analysis report

Static analysis result for SHA-256 81c357f9ef20df8f…

MALICIOUS

PDF

84.2 KB Created: 2021-06-29 11:44:13 +03:00 Authoring application: wkhtmltopdf 0.12.5 (via Qt 5.11.3)
MD5: 5f4eae681798c4f8c646ce2ce3989a17 SHA-1: e1c83ca7e8e5c8d4cf267ab7857e5a5e44b1646f SHA-256: 81c357f9ef20df8f4318d5999c59b52d76f7d4b56e4a8c43f7620596e0158136
156 Risk Score

Malware Insights

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

The PDF contains numerous embedded URLs, many of which point to external websites, including those hosted on compromised CMS upload storage. The ML classifier and ClamAV detection strongly indicate malicious intent, likely for phishing or distributing further malware. The document body is heavily obfuscated and unreadable, providing no direct user-facing content, but the heuristic firings clearly point to a link farm strategy.

Machine Learning

  • Nyx PDF Classifier malicious score 0.9992

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://avflash.nl/upload/files/31246172296.pdf
    • http://stroisvias.ru/userfiles/file/luwomixifupig.pdf
    • http://olimpic.hu/ckfinder/userfiles/files/farevazolilawazojoniko.pdf
    • http://klingende-zeder.de/wp-content/plugins/formcraft/file-upload/server/content/files/160943e81ab72a---xamego.pdf
    • https://signaturetowerpune.com/wp-content/plugins/super-forms/uploads/php/files/b30jn9r5ivu2mh9tk4foketlp5/xebuj.pdf
    • https://infrastone.com/userfiles/files/97779334449.pdf
    • https://sodigital.it/wp-content/plugins/formcraft/file-upload/server/content/files/160d2144a87f76---larupisanen.pdf
    • http://www.advokat.com/app/webroot/img/fck/file/77343539332.pdf
    • http://ngpsusa.com/wp-content/plugins/super-forms/uploads/php/files/oqdthrbe7n7qoilkd1f12aensj/22043390622.pdf
    • http://www.veronicaneal.com/wp-content/plugins/formcraft/file-upload/server/content/files/1/16088717f31a12---vefitib.pdf
    • http://studioaba.net/userfiles/files/jisowavujuxilomig.pdf
    • https://smilepath.com.au/wp-content/plugins/super-forms/uploads/php/files/71e9a0222d0e2cbef8438ab9d222751b/64865991728.pdf
    • https://idfusionllc.com/wp-content/plugins/super-forms/uploads/php/files/a4c8e22e12d37c88d0338944541e9d23/30785582933.pdf
    • https://creationstationdance.com/wp-content/plugins/formcraft/file-upload/server/content/files/1607e08abda849---xevomaf.pdf
    • http://atomleasing.ru/media/File/86561854078.pdf
    • https://postscriptproductions.com/wp-content/plugins/formcraft/file-upload/server/content/files/1607c7b3f3f87b---98725312942.pdf
    • https://areicon.com/images/file/zefovozupevulenudedodunon.pdf
    • https://tucarrorentacar.co/ckfinder/userfiles/files/21662099935.pdf
    • https://www.treehousecare.org/wp-content/plugins/formcraft/file-upload/server/content/files/1606fd63f50da9---kexawuwigusosiz.pdf
    • https://www.novet.de/wp-content/plugins/formcraft/file-upload/server/content/files/160729beaba3fe---lezomezoditipixanisawix.pdf
    • https://feedproxy.google.com/~r/skout/mBVl/~3/FevRqgeaUVY/uplcv?utm_term=carpal+tunnel+dr+near+me
    • 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_off0000eaf9.bin
f19216de0989c45e0cf4be1e8ebb0b6b606a668f1af38fdcfd03814724503909
pdf-font-stream PDF embedded font (sfnt) at offset 0xEAF9 16148 bytes
font_01_sfnt_off000114ae.bin
415393976b54b459b3f795002f067af807961ef9285323fb48ea508b62d9112f
pdf-font-stream PDF embedded font (sfnt) at offset 0x114AE 10304 bytes
font_02_sfnt_off00012bda.bin
9d2294e344127da9ddc2b77d68b1576b6b78373885bc9da2859f180a98f2c1e1
pdf-font-stream PDF embedded font (sfnt) at offset 0x12BDA 16792 bytes