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ALPHV/BlackCat Ransomware Group Claims Responsibility for MGM Resorts Attack

Cyber Threats

Threat Actors

Summary

The ALPHV/ BlackCat ransomware group claimed responsibility for the MGM Resorts cyberattack in September 2023. The attack disrupted MGM’s operations, including slot machines, ATMs, and payment systems, causing significant financial and operational damage. Arete’s detailed analysis highlights ALPHV/BlackCat’s methodologies and the sectors affected by their attacks.

MGM Resorts recently identified a cybersecurity issue affecting certain of the Company’s systems. Promptly after detecting the issue, we began an investigation with assistance from leading external cybersecurity experts. We also notified law enforcement and are taking steps to protect our systems and data, including shutting down certain systems. Our investigation is ongoing, and we are working diligently to resolve the matter. The Company will continue to implement measures to secure its business operations and take additional steps as appropriate.

This incident also resulted in significant financial impact. According to NASDAQ, shares of the company’s stock have fallen 7.9%, from $43.74 to $40.29, between September 8 and 18.

The ALPHV (aka BlackCat) ransomware group claimed responsibility for this attack.

Update from ALPHV’s Dark Web Site

Arete has gained a deep understanding of ALPHV/BlackCat operations by working with nearly 100 clients impacted by the ransomware group since 2021. Arete’s Threat Intelligence team monitors multiple data leak sites and discovered that on September 14, the ALPHV group claimed they gained access to the MGM network on September 8. After multiple failed attempts to get in touch with the victim, ALPHV released their ransomware payload to more than 100 ESXi hypervisors in MGM’s network environment:

Source: Arete


Source: Arete


In this post, the group states:

“Their network has been infiltrated since Friday.”

“After waiting a day, we successfully launched ransomware attacks against more than 100 ESXi hypervisors in their environment on September 11th after trying to get in touch but failing. This was after they brought in external firms for assistance in containing the incident.”

“The ALPHV ransomware group has not before privately or publicly claimed responsibility for an attack before this point.”

“We still continue to have access to some of MGM’s infrastructure. If a deal is not reached, we shall carry out additional attacks. We continue to wait for MGM to… reach out as they have clearly demonstrated that they know where to contact us.”

Insights on ALPHV/BlackCat

Arete’s mid-year Turning Tides – Navigating the Evolving World of Cybercrime, highlighted ALPHV/BlackCat as one of the top ransomware groups observed in the second half of 2022 (H2 2022) and the first half of 2023 (H1 2023) based on data from our incident response engagements.

Source: Arete

Additional data also reveals that ALPHV/BlackCat remains one of the top three threat actor groups observed by Arete since Q3 of 2022.

Source: Arete

Below are insights on ALPHV based on Arete’s incident response engagements:

  • Sectors affected include entertainment, critical infrastructure, financial services, healthcare, manufacturing, professional services, public services, and retail.

  • Average ransom demand: $1,992,971

  • Percentage of time data exfiltration occurs: 70%

  • Average business downtime: 5.3 days

  • Tools used: CobaltStrike, Mimikatz, Megasync, LaZagne, and WebBrowserPassView

  • ALPHV/BlackCat uses various entry points to infect the victim’s network, including phishing emails, compromised credentials, and remote desktop protocol (RDP) brute force attacks.

  • Other malware is used as a stepping stone to launch the ransomware payload.

  • To increase potential reach and impact, the group targets both Windows and Linux devices, as well as network-attached storage (NAS) devices, which are often used to store backups and sensitive data.

To learn more about ALPHV/BlackCat and how to protect your organization from cyberattacks, download Turning Tides – Navigating the Evolving World of Cybercrime.

Our team of experts is here to assist you with this and any other related cyber incidents. Available services include Incident Response & Forensics, Threat Actor Negotiations, Crypto Operations, Security Operations (SOC), Restoration, and Threat Intelligence.

Cyber Emergency Hotline: 866.210.0955

New Engagements: Arete911@AreteIR.com

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Top 9 Security Controls for SMBs

In today’s complex cyber threat landscape, small and medium-sized businesses (SMBs) should implement a layered, multi-pronged approach to security. Here are some proven, effective controls to consider:

1.        Implement MFA for All Users
Multi-factor authentication (MFA) is an effective and accessible way to protect sensitive data, comply with regulatory standards, and prevent unauthorized access to critical systems. By ensuring that users not only use a password but also a secure token, an organization can significantly reduce phishing attempts, credential stuffing attacks, and ransomware incidents. MFA should be enabled for email, VPN, and critical system access.

2.        Update Patch Management Programs
A modern patching program should include policies and mechanisms to manage software updates in a timely manner. Patching efforts should address not just operating system updates, but also commonly utilized software within the environment. An active patching plan aims to reduce the mean time to patch and provide metrics on existing patch efforts. In the event of a high-severity vulnerability, a mature patching program should also be able to identify the risks and exposure for a given set of systems based on the average time to patch. This helps stakeholders make informed decisions when a new exploit is released.

3.        Leverage a Properly Managed Endpoint Detection and Response (EDR) Tool
With real-time threat detection and advanced visibility, endpoint detection and response (EDR) solutions can enhance an organization’s ability to detect and investigate potential malicious activity, including ransomware, lateral movement, fileless attacks, and more. Effective management of EDR should include proper configuration, regular agent updates, and established procedures for responding to alerts.

4.        Enhance EDR with Frontline Incident Intelligence
While EDR solutions are an important component of a security program, threat actors are continually adapting their techniques to evade detection, and as a result, standard detection methods may not always identify emerging threats or novel attack behaviors. To strengthen protection, organizations can supplement EDR tools with custom detection rules informed by incident response data. These rules can help identify indicators of compromise observed during cyber incidents, providing an additional layer of visibility beyond traditional detections.

Arete Bloktd℠ illustrates this approach by transforming threat intelligence and malware analysis into curated detection rules for EDR tools. Applying frontline intelligence to security tools can result in earlier detection, less investigative burden, and a more confident response. 

5.        Create and Continuously Test an Incident Response (IR) Plan
An incident response plan can help an organization effectively identify, respond to, and recover from a cybersecurity incident while minimizing disruption and downtime. An IR plan defines clear roles, escalation paths, communication strategies, and decision frameworks for both internal and external teams. To be effective, these plans should be regularly tested with post-incident reviews or tabletop exercises involving key stakeholders.

6.        Maintain Encrypted and Tested Data Backups
In the case of a cyberattack, backups can help organizations maintain business continuity, support ransom negotiations with threat actors, and contribute to a timely and successful recovery. Encrypting backups makes it more difficult for threat actors to access or alter them, and regular testing ensures they remain accessible during a security incident.

7.        Conduct Employee Security Awareness Training
Human error is a leading cause of cybersecurity incidents, and an organization’s employees are its first line of defense against cyber threats. Security awareness training reinforces the importance of data confidentiality, supports regulatory compliance, and helps employees recognize and understand red flags such as suspicious emails, malicious links, and social engineering attempts.

8.        Assess and Address Existing Risk and Vulnerabilities
To maintain a proactive approach to risk management and improve resilience, organizations should regularly assess existing vulnerabilities through expert-led Vulnerability Assessments, Penetration Testing, and Threat Hunting Assessments. These exercises can help identify security gaps, support regulatory compliance, and prevent potential incidents. During remediation, prioritize high-impact vulnerabilities and make a plan for periodic assessments.

9.        Apply Least-Privilege Access Controls
Employees should have access only to the systems, applications, and data necessary to perform their jobs. By removing unnecessary administrative privileges and regularly reviewing user permissions, organizations can reduce the risk of unauthorized access and limit the damage caused by compromised accounts or insider threats.

Organizations should regularly review their cybersecurity programs, stay informed about emerging threats, and evaluate whether their security controls are adapting to the evolving threat landscape.

Article

Ransomware Trends & Data Insights: August 2026

Although INC Ransom was the most active ransomware threat group observed in August 2026, overall activity remained relatively distributed across the threat landscape, with approximately 30 unique ransomware and extortion groups, including both established and newly emerged actors, observed during the month. Alongside INC Ransom, Storm, DragonForce, Qilin, and The Gentlemen were among the top five most active threat groups, underscoring the continued diversity and competitiveness of the ransomware ecosystem.

Figure 1. Activity from the top 5 threat groups in August 2026 

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

  • August 2026 was a significant month for the emergence of new threat actors, with Arete identifying several previously untracked ransomware groups, including Storm, Dark Project, DireWolf, Morpheus, Orova, Spirals, Wallstreet Team, and Zawoo Team. This trend underscores the ongoing evolution of the threat landscape and the low barriers to entry for new cybercriminal operations. 

  • Arete observed a continued use of AI-enabled capabilities across the ransomware ecosystem during August. Similar to Fulcrumsec and Setra, the newly emerged Zawoo Team appears to leverage AI-assisted analysis of stolen data, publishing highly structured and detailed victim assessments on its data leak site (DLS). Additionally, both the Aurora and Storm ransomware groups have been observed utilizing AI-driven or AI-assisted chat representatives during victim communications. These developments suggest that threat actors are increasingly incorporating AI to enhance data analysis, automate victim engagement, and improve the effectiveness and scalability of extortion operations. 

  • In August, Arete also observed that despite sustained law enforcement disruption efforts, LockBit continues to demonstrate operational resilience, likely through the expansion of its affiliate ecosystem and the evolution of its tactics. Recent activity indicates an increased reliance on data theft and exfiltration-only operations, with observed victimology suggesting a notable focus on organizations within the financial sector. 

Sources

  • Arete Internal

Report

Arete's H1 2026 Crimeware Report

Explore intelligence and operational data from the frontlines of ransomware and extortion response as we detail the most significant trends and developments in the cyber threat landscape in the first half (H1) of 2026.

Article

WinRAR Path-Traversal Vulnerability Exploited in Ransomware Attacks

CISA has warned that CVE-2025-8088, a path-traversal vulnerability in WinRAR, is being exploited in ransomware attacks. The vulnerability allows attackers to use specially crafted archive files to place malicious executables in locations such as the Windows Startup folder, enabling code execution when the system restarts. WinRAR addressed this vulnerability in version 7.13, but exploitation has continued due to challenges in updating the software. CISA's updated KEV entry now specifically identifies the vulnerability as being used in ransomware attacks. 

What’s Notable and Unique

  • The vulnerability was initially exploited as a zero-day by the Russia-linked RomCom group, enabling malware execution at user logon and supporting credential theft, cyberespionage, and ransomware-related activities.

  • CVE-2025-8088 continues to be actively exploited by both government-backed and financially motivated threat actors. Observed campaigns have been attributed to Russian- and Chinese-linked groups targeting several organizations.

  • Phishing campaigns leveraging weaponized RAR attachments exploited CVE-2025-8088 to silently place malicious payloads in autorun locations using directory traversal and Alternate Data Streams (ADS). 

  • The widespread exploitation of CVE-2025-8088 highlights strong demand for effective WinRAR exploits, with multiple underground vendors previously supplying exploit capabilities to a diverse range of threat actors. One such vendor, zeroplayer, advertised a WinRAR exploit in July 2025. 

Analyst Comments

Organizations should immediately upgrade WinRAR to version 7.13 or later and conduct an enterprise-wide inventory to identify unmanaged installations. Given that WinRAR lacks automatic updates, Group Policy support, and integration with common enterprise patch management platforms, manual verification and remediation may be required to ensure all vulnerable instances are addressed. Security teams should also enhance defenses against archive-based phishing attacks by blocking or scrutinizing unsolicited compressed files, monitoring for suspicious file creation in Windows Startup directories, and detecting abuse of ADS. With CISA now linking CVE-2025-8088 to ransomware activity, organizations should treat remediation as a high priority and actively monitor for indicators of WinRAR-based exploitation across their environments.

Sources

  • CISA Adds Three Known Exploited Vulnerabilities to Catalog

  • WinRAR vulnerability being exploited in ransomware attacks, CISA warns