Daily CISO Briefing Note | December 5, 2025

Welcome reader, here’s today’s Cyber Briefing Note.

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Summary

The past 48 hours included a joint government advisory from United States and Canadian agencies regarding backdoor malware targeting virtualization infrastructure, a national computer emergency response disclosure from Japan confirming active exploitation of a VPN gateway vulnerability, security vendor research documenting a false flag operation using productivity software lures, and a security vendor threat report detailing record-level distributed denial of service activity from a botnet-for-hire. These disclosures surfaced from unrelated sectors within the same reporting window through coordinated government disclosure timelines and independent security research publication schedules.

Theme 1: Joint United States and Canadian advisory documents backdoor malware targeting VMware virtualization infrastructure

The Cybersecurity and Infrastructure Security Agency, National Security Agency, and Canadian Centre for Cyber Security released a joint malware analysis report on BRICKSTORM, a Go-based backdoor targeting VMware vSphere and Windows environments. The advisory documents activity from April 2024 through September 2025 against government and information technology sector organizations. The implant maintains persistence through self-monitoring functions and employs DNS-over-HTTPS to conceal command-and-control communications. The report includes eight malware samples and YARA detection signatures. Source category: government advisory. Executive relevance sits in the dependency on virtualization platforms hosting domain controllers and identity infrastructure within enterprise environments.

Theme 2: Japan national CERT confirms active exploitation of VPN gateway command injection vulnerability

JPCERT/CC issued an advisory confirming active exploitation of a command injection vulnerability in Array Networks ArrayOS AG Series secure access gateways since August 2025. The vulnerability resides in the DesktopDirect remote desktop access feature and allows arbitrary command execution without authentication. Confirmed incidents in Japan involved webshell deployment in the /ca/aproxy/webapp/ path. Array Networks addressed the vulnerability in ArrayOS version 9.4.5.9 released May 2025; no CVE identifier has been assigned. Source category: national CERT advisory. Executive relevance sits in the presence of VPN gateway appliances providing remote access to internal network resources and hosted applications.

Theme 3: Security vendor research documents productivity software impersonation campaign delivering remote access trojan

ReliaQuest published research identifying a campaign attributed to Silver Fox deploying ValleyRAT through trojanized installers impersonating Microsoft Teams, Telegram, WinSCP, and Google Chrome. The campaign employs SEO poisoning and targets Chinese-speaking users, including those within Western organizations operating in China. The malware chain includes Microsoft Defender exclusion manipulation, vulnerable driver deployment for endpoint security termination, and persistence through scheduled tasks executing encoded VBScript. The loader contains Cyrillic elements assessed as deliberate false flag indicators. Source category: security vendor research. Executive relevance sits in the use of productivity collaboration platforms as initial access vectors across multinational workforce environments.

Theme 4: Security vendor threat report documents record distributed denial of service activity from botnet-for-hire

Cloudflare published its Q3 2025 DDoS Threat Report documenting activity from the AISURU botnet, an estimated one-to-four million infected host network. The report describes a 29.7 Tbps UDP carpet-bombing attack lasting 69 seconds, representing the largest volumetric attack recorded. Cloudflare mitigated 2,867 AISURU attacks since January 2025, with hyper-volumetric attacks averaging 14 per day during Q3. The botnet targeted telecommunications, financial services, gaming, and hosting provider organizations. Source category: security vendor research. Executive relevance sits in the dependency on internet-facing service availability and content delivery infrastructure supporting customer and workforce access.

Synthesis

Multiple unrelated sectors appeared within the same reporting window through government advisory coordination, national CERT disclosure timelines, and independent security vendor research publication schedules.

Author
Daniel Michan is the founder of CybersecurityHQ, a CISO-grade intelligence platform read weekly across the Fortune 100. He analyzes identity-centric risk, machine identity failures, SaaS integration breakdowns, and emerging AI-speed threats, producing executive briefings and deep-dive research used by enterprise security leaders for decision support.