--- title: OXLOADER: new loader evading detection to drop... description: Elastic Security Labs has uncovered OXLOADER, a previously undocumented Windows malware loader distributed via malicious Google Ads impersonating Node.js. The... canonical: https://daily.dev/posts/oxloader-new-loader-evading-detection-to-drop-infostealer-elastic-security-labs-zbtmpxfpn twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: OXLOADER: new loader evading detection to drop infostealer — Elastic Security Labs | daily.dev og:description: Elastic Security Labs has uncovered OXLOADER, a previously undocumented Windows malware loader distributed via malicious Google Ads impersonating Node.js. The... og:url: https://daily.dev/posts/oxloader-new-loader-evading-detection-to-drop-infostealer-elastic-security-labs-zbtmpxfpn og:image: https://api.daily.dev/og/posts/ZBTMpXfPN.png og:image:alt: OXLOADER: new loader evading detection to drop infostealer — Elastic Security Labs og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # OXLOADER: new loader evading detection to drop infostealer — Elastic Security Labs **[Elastic Security Labs](https://daily.dev/sources/elastic-security-labs)** · 10 min read · 2 upvotes · 0 comments ## Summary Elastic Security Labs has uncovered OXLOADER, a previously undocumented Windows malware loader distributed via malicious Google Ads impersonating Node.js. The loader delivers the CASTLESTEALER infostealer and achieves low detection rates through multiple obfuscation layers (control-flow flattening, mixed Boolean-Arithmetic, opaque predicates), self-modifying decryption stubs, and an unusual technique of staging shellcode inside the PE .reloc section via a copied .ocx file. Anti-sandbox checks include CPU count (≥3), RAM (≥3 GB), display refresh rate (≥20 Hz), and geographic/language exclusions targeting CIS regions and Russian-language systems, suggesting a financially motivated Russian-speaking threat actor. The final payload is delivered in-memory via DonutLoader wrapping the CASTLESTEALER .NET assembly. YARA rules and behavioral detection signatures are provided. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### What is the OXLOADER malware loader and how does it evade detection? OXLOADER is a Windows loader that delivers the CASTLESTEALER infostealer, using control-flow flattening, opaque predicates, mixed Boolean-Arithmetic obfuscation, and self-modifying decryption stubs. It abuses the executable's .reloc section to stage shellcode instead of legitimate relocation data, and performs anti-VM checks like CPU count, RAM, display refresh rate, and CIS/Russian-language exclusions, achieving low detection rates across static and sandbox engines. _Security teams tracking emerging evasive loaders can follow threat research breakdowns like this on daily.dev._ ### How is the CASTLESTEALER infostealer being distributed through malicious Google Ads? CASTLESTEALER is distributed via Google Ads impersonating Node.js, redirecting victims through an intermediary domain (app.miloyannopoulos.com) to a Storj-hosted batch script that downloads OXLOADER. The batch script shows a fake installer UI, fetches the payload via PowerShell with UAC elevation, and eventually loads CASTLESTEALER in memory using DonutLoader with Chaskey-LTS encrypted configuration. _Analysts investigating malvertising campaigns can dig into detailed IOC and technique writeups on daily.dev._ ### How does malware detect sandbox environments using CPU count and display refresh rate checks? OXLOADER requires at least 3 CPUs and 3 GB of physical RAM to continue execution, since many sandboxes are provisioned with fewer resources to conserve overhead. It also queries the display refresh rate via WMI's Win32_VideoController class, expecting at least 20 Hz, because headless or default virtualized configurations typically report 0 or 1 Hz, causing the loader to abort if these thresholds aren't met. _Reverse engineers researching anti-analysis techniques can find similar evasion breakdowns on daily.dev._ ## Similar posts on daily.dev - [Stealth in Layers: Unmasking the Loader used in Targeted Email Campaigns](https://daily.dev/posts/stealth-in-layers-unmasking-the-loader-used-in-targeted-email-campaigns-xfgpoq8c1) · Cyble · 0 upvotes · 0 comments - [Inside .NET Loader Analysis: From Malspam to In-Memory Loader](https://daily.dev/posts/inside-net-loader-analysis-from-malspam-to-in-memory-loader-tafajwltg) · Huntress Blog · 4 upvotes · 0 comments --- Tags: [#security](https://daily.dev/tags/security), [#malware](https://daily.dev/tags/malware) [View this post on daily.dev](https://daily.dev/posts/oxloader-new-loader-evading-detection-to-drop-infostealer-elastic-security-labs-zbtmpxfpn) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"OXLOADER: new loader evading detection to drop infostealer — Elastic Security Labs","url":"https://daily.dev/posts/oxloader-new-loader-evading-detection-to-drop-infostealer-elastic-security-labs-zbtmpxfpn","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/oxloader-new-loader-evading-detection-to-drop-infostealer-elastic-security-labs-zbtmpxfpn"},"datePublished":"2026-06-18T17:27:20.042Z","dateModified":"2026-09-13T21:14:24.327Z","description":"Elastic Security Labs has uncovered OXLOADER, a previously undocumented Windows malware loader distributed via malicious Google Ads impersonating Node.js. 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