Article
Fool Us Once … BlackMatter Initial Access Tactics Point to a Possible REvil Association
Arete Analysis
Cyber Threats
Threat Actors
By Kevin Baker
Arete observed an overlap between a recent BlackMatter case and a Q1 2021 REvil case. In both instances, the actors leveraged the NodeJS-based Gootloader to deliver a CobaltStrike payload.
In a March 2021 insight, Arete detailed findings related to complex watering-hole infrastructure used to deliver Gootloader to unsuspecting victims. Highlights included:
REvil actors leveraged compromised web servers of legitimate businesses to host Gootloader.
Actors leveraged search engine optimization (SEO) hijacking to push malicious results to the top.
The malicious search results led to an actor-controlled site masquerading as a legitimate messaging board.
The board contained fake posts by different users, including an “admin” account (Figure 1).
The download link in Figure 1 led to a JS-payload that installed a CobaltStrike (CS) beacon.
The actor leveraged CS to move laterally within the victim’s network to deploy and execute the REvil ransomware.
Figure 1 – Actor-controlled forum and fake posts (Source: Arete Forensics Insight)
While watering-hole attacks have been around for years, Arete did not previously observe this specific watering-hole site configuration in the wild or associated with ransomware threat group activity until this specific REvil investigation and response in Q1 2021. Fast forward a few months and REvil is no longer operational and their infrastructure (e.g., communication site, storage sites) is offline. The cause of the REvil’s disappearance is unknown, but the group’s tactics, techniques, and procedures (TTPs) live on with another group: BlackMatter.
In August 2021, Arete was engaged to investigate and respond to a BlackMatter ransomware attack that impacted a law practice in the Midwest United States. Forensic timeline analysis of the observed indicators of compromise (IoCs) led Arete to assess that while the BlackMatter ransomware payload was detonated in August 2021, the initial compromise originally occurred in May 2021 and was attributed to the same type of Gootloader JS payload that impacted the professional services organization we assisted in Q1 2021.
Analysis indicated that in early May 2021, an employee of the victim organization searched in Google for “intercompany agreement transfer pricing sample.” As was the case with the Q1 2021 REvil incident, the actors leveraged SEO hijacking to prioritize the Gootloader infected pages. Arete observed that several keywords were altered to reflect the employee’s search terms (Figure 2).
Figure 2 – Gootloader watering hole leads to BlackMatter ransomware deployment.
When compared side by side with the Gootloader watering hole REvil leveraged in Q1 2021, these pages are nearly identical (save for a different link, a different title of the document the user was searching for, and some slight modification to the icons of the fake forum users). Arete observed similarities between the watering hole leveraged by REvil and the watering hole leveraged by BlackMatter (Figure 1, Figure 3, and Figure 4). Similar behavior was previously reported for other Gootloader campaigns, including but not limited to matching “forum themes” and multi-language versions of the forums.
Figure 3 – Comparing REvil to BlackMatter Gootloader-involved attack lifecycle.
Figure 4 – Gootloader JS payload diff.
Dynamic analysis of the BlackMatter Gootloader sample resulted in different domain callouts for command-and-control (C2) infrastructure when compared against the older Gootloader sample associated with the Q1 2021 REvil attack. Those domain callouts are documented below for incorporation into EDR/HIDS/NIDS:
While it’s impossible to confirm with absolute certainty the linkage between REvil and BlackMatter, it is notable that both groups share a similar initial access tactic of leveraging fake forum posts weaponized with Gootloader, coupled with SEO hijacking, to gain an initial foothold in targeted environments.
The Arete Threat Intelligence and Forensics teams continue to monitor any potential changes to TTPs for BlackMatter or the re-emergence of REvil.
Acknowledgements
Arete would like to acknowledge the contributions of Senior Forensic Analyst Robert Christine for documenting and timelining the indicators and observables that led to this discovery.
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FortiGate Exploits Enable Network Breaches and Credential Theft
A recent security report indicates that threat actors are actively exploiting FortiGate Next-Generation Firewall (NGFW) appliances as initial access vectors to compromise enterprise networks. The activity leverages recently disclosed vulnerabilities or weak credentials to gain unauthorized access and extract configuration files, which often contain sensitive information, including service account credentials and detailed network topology data.
Analysis of these incidents shows significant variation in attacker dwell time, ranging from immediate lateral movement to delays of up to two months post-compromise. Since these appliances often integrate with authentication systems such as Active Directory and Lightweight Directory Access Protocol (LDAP), their compromise can grant attackers extensive access, substantially increasing the risk of widespread network intrusion and data exposure.
What’s Notable and Unique
The activity involves the exploitation of recently disclosed security vulnerabilities, including CVE-2025-59718, CVE-2025-59719, and CVE-2026-24858, or weak credentials, allowing attackers to gain administrative access, extract configuration files, and obtain service account credentials and network topology information.
In one observed incident, attackers created a FortiGate admin account with unrestricted firewall rules and maintained access over time, consistent with initial access broker activity. After a couple of months, threat actors extracted and decrypted LDAP credentials to compromise Active Directory.
In another case, attackers moved from FortiGate access to deploying remote access tools, including Pulseway and MeshAgent, while also utilizing cloud infrastructure such as Google Cloud Storage and Amazon Web Services (AWS).
Analyst Comments
Arete has identified multiple instances of Fortinet device exploitation for initial access, involving various threat actors, with the Qilin ransomware group notably leveraging Fortinet device exploits. Given their integration with systems like Active Directory, NGFW appliances remain high-value targets for both state-aligned and financially motivated actors. In parallel, Arete has observed recent dark web activity involving leaked FortiGate VPN access, further highlighting the expanding risk landscape. This aligns with the recent reporting from Amazon Threat Intelligence, which identified large-scale compromises of FortiGate devices driven by exposed management ports and weak authentication, rather than vulnerability exploitation. Overall, these developments underscore the increasing focus on network edge devices as entry points, reinforcing the need for organizations to strengthen authentication, restrict external exposure, and address fundamental security gaps to mitigate the risk of widespread compromise.
Sources
FortiGate Edge Intrusions | Stolen Service Accounts Lead to Rogue Workstations and Deep AD Compromise
Article
Vulnerability Discovered in Anthropic’s Claude Code
Security researchers discovered two critical vulnerabilities in Anthropic's agentic AI coding tool, Claude Code. The vulnerabilities, tracked as CVE-2025-59536 and CVE-2026-21852, allowed attackers to achieve remote code execution and to compromise a victim's API credentials. The vulnerabilities exploit maliciously crafted repository configurations to circumvent control mechanisms. It should be noted that Anthropic worked closely with the security researchers throughout the process, and the bugs were patched before the research was published.
What’s Notable and Unique
The configuration files .claude/settings.json and .mcp.json were repurposed to execute malicious commands. Because the configurations could be applied immediately upon starting Claude Code, the commands ran before the user could deny permissions via a dialogue prompt, or they bypassed the authentication prompt altogether.
.claude/settings.json also defines the endpoint for all Claude Code API communications. By replacing the default localhost URL with a URL they own, an attacker could redirect traffic to infrastructure they control. Critically, the authentication traffic generated upon starting Claude Code included the user's full Anthropic API key in plain text and was sent before the user could interact with the trust dialogue.
Restrictive permissions on sensitive files could be bypassed by simply prompting Claude Code to create a copy of the file's contents, which did not inherit the original file's permissions. A threat actor using a stolen API key could gain complete read and write access to all files within a workspace.
Analyst Comments
The vulnerabilities and attack paths detailed in the research illustrate the double-edged nature of AI tools. The speed, scale, and convenience characteristics that make AI tools attractive to developer teams also benefit threat actors who use them for nefarious purposes. Defenders should expect adversaries to continue seeking ways to exploit configurations and orchestration logic to increase the impact of their attacks. Organizations planning to implement AI development tools should prioritize AI supply-chain hygiene and CI/CD hardening practices.
Sources
Caught in the Hook: RCE and API Token Exfiltration Through Claude Code Project Files | CVE-2025-59536 | CVE-2026-21852
Article
Ransomware Trends & Data Insights: February 2026
After a slight lull in January, Akira and Qilin returned to dominating ransomware activity in February, collectively accounting for almost half of all engagements that month. The rest of the threat landscape remained relatively diverse, with a mix of persistent threats like INC and PLAY, older groups like Cl0p and LockBit, and newer groups like BravoX and Payouts King. Given current trends, the first quarter of 2026 will likely remain relatively predictable, with the top groups from the second half of 2025 continuing to operate at fairly consistent levels month to month.
Figure 1. Activity from the top 5 threat groups in February 2026
Throughout the month of February, analysts at Arete identified several trends behind the threat actors perpetrating cybercrime activities:
In February, Arete observed Qilin actively targeting WatchGuard Firebox devices, especially those vulnerable to CVE-2025-14733, to gain initial access to victim environments. CVE-2025-14733 is a critical vulnerability in WatchGuard Fireware OS that allows a remote, unauthenticated threat actor to execute arbitrary code. In addition to upgrading WatchGuard devices to the latest Firebox OS version, which patches the bug, administrators are urged to rotate all shared secrets on affected devices that may have been compromised and may be used in future campaigns.
Reports from February suggest that threat actors are increasingly exploring AI-enabled tools and services to scale malicious activities, demonstrating how generative AI is being integrated into both espionage and financially motivated threat operations. The Google Threat Intelligence Group indicated that state-backed threat actors are leveraging Google’s Gemini AI as a force multiplier to support all stages of the cyberattack lifecycle, from reconnaissance to post-compromise operations. Separate reporting from Amazon Threat Intelligence identified a threat actor leveraging commercially available generative AI services to conduct a large-scale campaign against FortiGate firewalls, gaining access through weak or reused credentials protected only by single-factor authentication.
The Interlock ransomware group recently introduced a custom process-termination utility called “Hotta Killer,” designed to disable endpoint detection and response solutions during active intrusions. This tool exploits a zero-day vulnerability (CVE-2025-61155) in a gaming anti-cheat driver, marking a significant adaptation in the group’s operations against security tools like FortiEDR. Arete is actively monitoring this activity, which highlights the growing trend of Bring Your Own Vulnerable Driver (BYOVD) attacks, in which threat actors exploit legitimate, signed drivers to bypass and disable endpoint security controls.
Sources
Arete Internal