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Threat Actors Exploiting New ESXi Vulnerability

Threat Actors

Cyber Threats

Combating Ransomware

In late July, researchers at Microsoft reported on an authentication bypass vulnerability in VMware ESXi that is being exploited by several ransomware groups, including Black Basta and Akira. The vulnerability, identified as CVE-2024-37085, allows a threat actor to create a group named “ESX Admins” on the Active Directory domain and add users to it. By default, any member of the group has full administrative access. With the vulnerability being actively exploited, it is recommended that organizations with domain-joined ESXi hypervisors install the update VMware released on their website to fix the issue.

What’s New and Notable

  •  CVE-2024-37085 can be exploited in several ways, either by adding an “ESX Admins” group to the domain and adding users to it or simply by renaming any group in the domain to “ESX Admins.”

  • Microsoft researchers observed threat actors earlier this year gaining initial access to a victim and then creating an “ESX Admins” group to encrypt the hosted virtual machines on the ESXi hypervisor with Black Basta ransomware.

  • In addition to installing VMware’s security update to fix the CVE-2024-37085 vulnerability, researchers also recommend users protect their privileged accounts from unauthorized users, identify any critical assets and potential vulnerabilities in their network, and maintain adequate monitoring, backups, and recovery plans.

Analyst Comments

VMware’s ESXi is a popular product used by thousands of organizations worldwide for virtualizing servers, which often host critical applications, data, and backups. As such, threat actors have increasingly targeted ESXi in recent years, with several threat groups deploying dedicated Linux encryptors for ESXi virtual machines. The latest vulnerability allows threat actors to gain privilege escalation, move laterally throughout the network, steal data, or deploy malicious payloads. Given this threat, organizations with domain-joined ESXi hypervisors should apply the available update provided by VMware. In addition to the software update and risk mitigation recommendations provided by researchers, organizations should also monitor their networks for signs of compromise and consider additional security measures to protect against vulnerabilities in the future.

Sources

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Article

Ransomware Trends & Data Insights: July 2026

INC Ransom was the most active threat group in July, while activity remained relatively distributed among multiple threat groups, with 19 unique groups observed throughout the month. Alongside INC Ransom, Qilin, Global Secret Group, Anubis, and DragonForce rounded out the five most active threat groups observed in July. Several emerging threat actors were also observed during the month, including Booba Team, Settra, and Global Secret Group.

Figure 1. Activity from the top 3 threat groups in July 2026

 Throughout the month, analysts at Arete identified several trends behind the threat actors perpetrating cybercrime activities:

  • In July 2026, Global Secret Group emerged as a new threat actor, leveraging the leaked LockBit 3.0 (LockBit Black) source code. Although the group began operations in June 2026, it quickly accumulated a substantial number of victims on its data leak site (DLS). The group operates through TOR-based negotiation portals and qTox communications. Notably, its DLS provides step-by-step guidance on purchasing Bitcoin, including references to Coinbase and Binance, demonstrating a streamlined, victim-focused extortion process designed to simplify ransom payments.

  • Similar to Fulcrumsec, the recently emerged Settra ransomware group appears to leverage AI-driven analysis of stolen data, publishing detailed and highly structured victim reports on its DLS. Additionally, a potential EDR-disabling tool, edr_blind.exe, was identified in multiple cases, suggesting a focus on defense-evasion capabilities.

  • With the continuation of the FortiBleed campaign, researchers have now identified compromised FortiGate credentials being leveraged by both the INC and Lynx ransomware operations. Analysis revealed direct operational links between the groups, including shared ransomware infrastructure and overlap between FortiBleed victims and ransomware targets. The operators are also incorporating AI to enhance various stages of the attack lifecycle and increase operational efficiency and scale. Notably, Arete also observed an INC ransomware intrusion leveraging FortiBleed-derived access in July, reinforcing the campaign's role as a precursor to ransomware deployment.

Sources

  • Arete Internal

Podcast

Cyber Campfire: June Threat Trends & Insights

In this episode of Arete’s Cyber Campfire podcast, our Threat Intelligence Team discusses trends, statistics, and emerging threat actors from June 2026. Tune in for firsthand insights on today’s threat landscape that can enhance your approach to cyber risk.

Article

Current: Misconfigured Server Reveals Multiple Phishing Campaigns

Researchers uncovered three Microsoft 365 phishing campaigns after discovering a misconfigured HTTP server that exposed a threat actor’s phishing tools, configurations, victim logs, and operational infrastructure. The investigation revealed two operators using custom Evilginx-based adversary-in-the-middle (AiTM) phishing frameworks to steal authentication sessions and bypass MFA protections. A third operator abused Microsoft’s OAuth Device Code flow by tricking victims into completing authentication through Microsoft’s legitimate login process, allowing attackers to obtain valid access and refresh tokens without stealing passwords. The largest campaign compromised at least 218 victims across 12 countries, primarily targeting corporate Microsoft 365 accounts, with refresh tokens enabling persistent access. Researchers also identified the use of remote management tools for maintaining access, AI-assisted development of phishing tooling, and links to broader Phishing-as-a-Service (PhaaS) ecosystems, highlighting how commodity frameworks and automation are lowering the barrier for sophisticated identity-based attacks.

What’s Notable and Unique

  • The campaigns demonstrate the continued shift from traditional credential theft to identity- and token-based compromise, in which attackers target authentication sessions, cookies, and OAuth tokens rather than relying solely on password theft. By obtaining valid authentication artifacts, attackers can access Microsoft 365 environments while bypassing conventional MFA protections.


  • The use of Evilginx-based AiTM frameworks highlights how publicly available phishing tools have evolved into effective MFA-bypass platforms. These frameworks proxy legitimate login pages, capture authenticated sessions, and allow attackers to reuse valid sessions without requiring victims’ credentials again.


  • The OAuth Device Code flow abuse represents a different attack method, in which attackers leverage a legitimate Microsoft authentication mechanism to obtain tokens after victims approve the request. This approach bypasses password theft entirely by abusing trusted authentication workflows.


  • The exposed infrastructure provided insight into attacker operations, including phishing configurations, victim tracking data, remote administration tools, and evidence of AI-assisted development. The findings demonstrate how phishing ecosystems now provide reusable tooling and automation that reduce the technical expertise required to conduct large-scale identity attacks.

Analyst Comments

These Microsoft 365 phishing campaigns demonstrate the ongoing evolution of identity-focused attacks, as adversaries increasingly target authentication sessions, tokens, and legitimate cloud authorization mechanisms to bypass traditional security controls. The combination of AiTM phishing, OAuth abuse, remote management tools, and PhaaS infrastructure enables threat actors to maintain persistent access while blending into legitimate cloud activity.

The growing availability of phishing frameworks and AI-assisted attack development highlights the need for continuous identity security improvements beyond traditional phishing defenses. Arete recommends that organizations strengthen identity monitoring, adopt phishing-resistant MFA where possible, review OAuth application permissions, monitor token activity, and implement conditional access policies to detect and restrict suspicious Microsoft 365 authentication behavior. Security teams should also monitor post-compromise indicators such as abnormal mailbox access, suspicious application consent, unauthorized remote tools, and unusual sign-in activity.

Sources

  • One Misconfigured Server, Three Active Campaigns: Full exposure of three AiTM Phishing Operators

  • Misconfigured Server Reveals Three Evilginx Phishing Operations Targeting Microsoft 365

Podcast

Digital Forensics Meets the Courtroom: Insights on Expert Witness and Cyber-Related Litigation

In this episode of Bytes of Insight, host Vinny Sakore and special guest Dr. Bruce Hartley, Managing Director and Co-Founder of Advisory Services at Arete, discuss the evolving role of digital forensics and expert witness work in cybersecurity litigation. Tune in for firsthand insights on how Arete conducts post-breach investigations, what it takes to undergo cross-examination on the stand, and how emerging threats like AI-driven social engineering and third-party breaches are reshaping the advisory landscape.