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Microsoft Exchange Server Zero Day Hack Insight

Arete Analysis

On March 2, 2021, Microsoft disclosed and provided security updates for four [4] critical vulnerabilities — CVE-2021-26855, CVE-2021-26857, CVE-2021-26858, and CVE-2021-27065 — impacting on-premises Microsoft Exchange Servers.

While Internet-facing Exchange Servers, such as Outlook Web Access systems, are at particular risk — and especially those at organizations without a dedicated Exchange Server administrator — Microsoft says the vulnerabilities do not impact Office 365/Exchange online mailboxes.

The Microsoft Threat Intelligence Center (MSTIC) attributes the activity to HAFNIUM, a Chinese state-sponsored threat group. Chinese state-sponsored threat actors historically target government agencies, higher-education institutions, law firms, defense contractors, policy think tanks, non-governmental organizations (NGOs), and most recently, infectious disease researchers.

IMMEDIATE ACTION: If you have not done so already, review the Microsoft advisories and apply patches to protect vulnerable systems.

Arete Contextual Insights

  • State-sponsored threat groups, such as HAFNIUM, have the time, skills, and resources to manufacture these potent vulnerability exploits. They are not, however, the only bad actors wielding these techniques.

  • Beyond what Chinese state-sponsored operations have perpetrated, Arete expects broad impact in high orders of magnitude across multiple industry verticals.

  • Since the disclosure, multiple security researchers have been analyzing the Exchange
    vulnerability patches. Arete can assert that cybercriminals and other state-sponsored actors are doing the same, most likely racing against patch cycles.

  • The Cybersecurity and Infrastructure Security Agency (CISA) and other high-fidelity sources estimate that tens of thousands of organizations are likely compromised. Via research channels, Arete is aware that one high-fidelity source provided Information Sharing and Analysis Centers (ISACs) with a list of approximately 12,000 organizations for victim notification.

  • Leveraging Microsoft resources, Arete has identified multiple impacted clients and is currently responding to exploitations across a broad variety of organizations from a variety of cybercrime actors deploying payloads, including, but not limited to, cryptomining malware and ransomware.

Follow-On Actions

Assess systems to validate compromise and analyze impact. Rapid identification and triage
analysis through deployment of SentinelOne and data collection scripts across the impacted Exchange Server(s) to identify malicious activity.

  • Implement protective measures to harden environments. Based on findings, deploy SentinelOne throughout the remainder of the environment to identify all instances of lateral movement, search for indicators of compromise (IOC’s), and provide insight into the current state of systems health throughout the environment.

Additional Defense Services Available

Managed Detection and Response (MDR) service combines cutting-edge machine learning and artificial intelligence technologies with insights from Arete cyber professionals to provide 24/7 monitoring, reporting, and defense against threats.

Cyber Strategy and Defense. Arete performs current-state testing to assess clients’ cyber hygiene and create a prioritized action plan that closes identified security gaps, strengthens existing infrastructure, and formalizes people, processes, and technologies into a robust cybersecurity program.

Cloud Advisory and Architecture Services. Arete helps clients navigate the shared responsibility model, advising on cloud architectures based on economics, business use, and security.

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Article

Europol Disrupts AudiA6 Crypto Laundering Service

European authorities have dismantled AudiA6, a major cryptocurrency laundering service linked to ransomware groups and broader cybercriminal networks. Between 2022 and 2025, the platform is believed to have processed over €336 million in illicit funds, enabling threat actors to obscure financial trails and monetize cybercrime proceeds. Its operators are also suspected of running Dark2Web, a dark web forum that facilitated collaboration, services, and connections among cybercriminals globally. This development underscores the expanding role of sophisticated, large-scale cryptocurrency laundering services in sustaining the cybercrime economy, enabling threat actors to obscure illicit funds and evade regulatory controls.

What’s Notable and Unique 

  • Following law enforcement disruption of Cryptex and Garantex, AudiA6 emerged as another platform involved in financial activities linked to ransomware groups. Investigators believe that AudiA6 became a central hub for cybercriminals seeking to launder stolen digital assets while obscuring the transaction trail from authorities.

  • On June 10, 2026, a coordinated operation resulted in two arrests in Georgia, the dismantling of key infrastructure (30+ servers, 25 domains), the freezing or seizure of over €778,000 in crypto, and the takedown of the AudiA6 and Dark2Web platforms. 

Analyst Comments

Ransomware groups and cybercriminal networks are increasingly leveraging sophisticated techniques, including chain-hopping, decentralized exchanges, and mixer-as-a-service platforms, to rapidly move illicit cryptocurrency across multiple blockchains, effectively obscuring transaction trails. Concurrently, the widespread use of fraudulent exchange accounts, mule wallets, and privacy-enhancing tools has elevated cryptocurrency laundering to a core enabler of the cybercrime ecosystem, allowing actors to bypass anti-money-laundering controls at scale. This investigation identified over 6,000 KYC records linked to money-mule accounts, many of which were tied to Russian-speaking intermediaries specifically recruited to facilitate the movement of illicit proceeds. These threat actors systematically used both commercial and domain-controlled email services to establish mule accounts across multiple cryptocurrency platforms. Collectively, these findings underscore the growing scale, coordination, and professionalization of cryptocurrency-enabled crime, highlighting the critical need for sustained, intelligence-led, and internationally coordinated efforts to disrupt these evolving financial ecosystems.

Sources

  • Ransomware gangs cut off from EUR 336 million ‘AudiA6’ crypto laundering pipeline

Article

Threat Actors Leverage AI for EDR Evasion

A threat actor has developed and deployed a ransomware attack toolkit enhanced with AI-assisted development workflows, enabling automated Active Directory (AD) discovery and improved EDR evasion capabilities. The toolkit leverages agent-based AI systems, such as Claude’s Opus and Cursor agents, for iterative malware development, testing, and refinement. 

What’s Notable and Unique 

  • Researchers have highlighted that this toolkit can not only generate ransomware code but also bypass sophisticated security defenses and identify AD networks for malware distribution. 

  • The framework incorporates multiple capabilities, including automated AD discovery and reconnaissance mechanisms, iterative EDR testing environments to refine evasion techniques, and a command-and-control (C2) infrastructure that leverages Telegram APIs and Cloudflare redirectors for stealth. 

  • Additionally, some agents were tasked with checking security research and technical posts for various bypass techniques. The agents recognized what was required for reproduction, extracted the techniques, mapped them to the MITRE ATT&CK knowledge base of adversary behaviors, set up a test lab, carried out the methodology, and reported the results. 

  • After a few repetitions, the modules seemed to avoid nearly all EDR solutions, despite the agent’s initial suggestion of a high failure rate. Although researchers found no evidence that AI was embedded in deployed malware or was operating independently in victim environments, the technology was still used to accelerate the iterative process of developing, testing, and refining payloads against security products, shortening the period between the publication of offensive security research and its practical implementation by threat actors. 

Analyst Comments 

AI-driven tools like this could accelerate the pace and sophistication of ransomware attacks, enabling even relatively inexperienced actors to launch high-impact campaigns. This development underscores the urgent need for security solutions to adapt to AI-assisted threats. Organizations must respond by strengthening detection engineering, improving visibility across environments, and maintaining robust security fundamentals.  

Sources 

  • AI-built ransomware toolkit automates EDR evasion, AD discovery  

  • Pointing a Cursor at evading detection

Article

Arete's 2026 Q1 Crimeware Report

Harness Arete’s unique data and expertise on extortion and ransomware to inform your response to the evolving threat landscape.

Article

CMS Vulnerability Leads to ClickFix Campaign

Threat actors compromised at least 700 education and technology websites in a recent ClickFix campaign by exploiting a critical SQL injection flaw (CVE-2026-26980) in the Ghost content management system (CMS). Adversaries combined the vulnerability with the ClickFix social engineering tactic to steal admin keys and inject a malicious JavaScript that delivers a fake Cloudflare or CAPTCHA verification pop-up, tricking victims into copying and pasting a malicious command into their systems.

What’s Notable and Unique

  • Rather than targeting the end user first, this campaign is unique in its initial exploitation of the system, followed by social engineering attempts. This hybrid attack style is likely being leveraged to bypass traditional defenses.

  • This recent campaign also highlights how trusted web properties can be weaponized at scale and coupled with unpatched CMS vulnerabilities. Rather than using the CMS compromise to perpetrate a single attack, threat actors turned it into a supply-chain attack that ultimately affected over 700 trusted websites.

Analyst Comments

As network defenders and their tools enhance threat detection capabilities, adversaries increasingly seek methods to bypass these defenses. By combining vulnerability exploitation, social engineering techniques, and staging for ancillary attacks, this campaign successfully bypassed traditional defenses and inflicted significant impact. Defending against hybrid cyberattacks requires comprehensive security controls beyond simply patching vulnerabilities. Organizations should focus on limiting movement within the environment, detecting abuse of trusted applications, and preventing end-user manipulation.

Sources

  • 700+ education and tech websites hijacked in huge ClickFix malware campaign

  • Under the engineering hood: Why Malwarebytes chose WordPress as its CMS

  • Think before you Click(Fix): Analyzing the ClickFix social engineering technique

  • Ghost CMS Vulnerability Exploited to Infect 700 Sites With ClickFix Malware