Malicious PDF — malware analysis report

Static analysis result for SHA-256 837c70a4c0252fa0…

MALICIOUS

PDF

69.1 KB Created: 2021-09-23 06:43:39 +03:00 Authoring application: wkhtmltopdf 0.12.5 (via Qt 5.11.3)
MD5: e1ccec4612483c5c24d90f1be8e3b8fe SHA-1: 1c466fbae0a1873c2954585d983b181c3f4a62b0 SHA-256: 837c70a4c0252fa03ac56b0e05635499caff90569053fbdf45439e6a635776ab
156 Risk Score

Malware Insights

MITRE ATT&CK
T1566.001 Spearphishing Attachment T1204.002 Malicious Link

The PDF file was flagged by multiple heuristics as a link farm, with numerous external URIs pointing to potentially compromised or disposable hosting. The ML classifier and ClamAV also identified it as malicious, specifically a phishing trojan. The document body is heavily obfuscated and appears to be generated by wkhtmltopdf, lacking clear user-facing content but containing numerous embedded URLs that likely lead to malicious sites.

Machine Learning

  • Nyx PDF Classifier malicious score 0.9982

Heuristics 6

  • ClamAV: Pdf.Phishing.Trojan-d2568dad23a94d95-d2568dad23a94d95-10044375-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Pdf.Phishing.Trojan-d2568dad23a94d95-d2568dad23a94d95-10044375-0
  • 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://crysiq.ru/uplcv?utm_term=bloatware+removal+tool+android
    • http://grupopiscis.com/upload/files/6902789816.pdf
    • http://cleannshieldflorida.com/wp-content/plugins/super-forms/uploads/php/files/64dcd983bc5a70e114201b09c0cdb60b/69126583240.pdf
    • http://taociren.com/upload/file/210911020343773501j6gor8ua9onc.pdf
    • http://chochosanencino.com/uploads/files/42299287829.pdf
    • http://jatyn.cn/upfiles/202109/file/1631233679.pdf
    • http://michalpavlicek.com/uploaded/file/gefejageboratadad.pdf
    • http://aotwresort.org/ckfinder/userfiles/files/5057955707.pdf
    • http://maquinandoysubastando.com/dleyes/admin/fotos/file/76059531168.pdf
    • http://xaydunganphubacninh.com/webroot/img/files/duvanevekijeforigewat.pdf
    • http://kapelski.pl/userfiles/file/mibaturo.pdf
    • http://tikatalog.sk/_files/file/6326304312.pdf
    • https://store-connector.com/_upload_bilder/_filemanager/file/wogimovuzinijovozovadidu.pdf
    • https://kamionosnyelvlecke.hu/userfiles/file/xekibosubazejevukunotopax.pdf
    • https://cananalimdar.com/wp-content/plugins/super-forms/uploads/php/files/mgjpq15l4912372446af207if5/soviwojipupiwomujaforobo.pdf
    • https://lorenzonimmigrationlaw.com/wp-content/plugins/formcraft/file-upload/server/content/files/16132af5726735---vavojopotirebesim.pdf
    • http://vanhacollection.com/images/files/16560866240.pdf
    • http://pobierzplik.pl/uploads/files/8715202728.pdf
    • http://culbertsonlawyer.com/customer/3/d/9/3d947ad6ce2568d98b832ccf5548371bFile/givuzeninonorigufuwax.pdf
    • http://autokolcsonzoszolnok.hu/admin/fck_upload/file/67696378783.pdf
    • http://artattack-concerts.de/files/file/rovabagakow.pdf
    • https://jewfri.kr/files/image/files/81957418590.pdf
    • https://ntiverification.com/userfiles/file/lezamemi.pdf
    • 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_off0000b1f6.bin
bbfc34db57642926f7caa4b92ad4c8097a16816f787375c404945b53dfc27cc1
pdf-font-stream PDF embedded font (sfnt) at offset 0xB1F6 14640 bytes
font_01_sfnt_off0000d6a4.bin
9d2294e344127da9ddc2b77d68b1576b6b78373885bc9da2859f180a98f2c1e1
pdf-font-stream PDF embedded font (sfnt) at offset 0xD6A4 16792 bytes
font_02_sfnt_off0000eebb.bin
2c4e2b5c61282b1bdd1c5e67f04e7540f363bcff30cfa89ff6155c3117f230d7
pdf-font-stream PDF embedded font (sfnt) at offset 0xEEBB 10444 bytes