Article
RansomHub: An Emerging Ransomware-as-a-Service
Combating Ransomware
Threat Actors

Since first emerging in February 2024, ransomware-as-a-service (RaaS) group RansomHub has added over 75 victims to its data leak site (DLS). Believed by the intelligence community to be a rebrand of the short-lived “Knight” ransomware group, RansomHub has already made a more significant impact than its alleged predecessor, based on the number of victims and high-profile targets. Recently, RansomHub was observed exploiting the Windows ZeroLogon vulnerability (CVE-2020-1472) for initial access into victim environments.
The Knight Ransomware Connection
Many intelligence communities believe RansomHub is a rebrand of Knight ransomware, which may be correct. However, there is an interesting timeline that paints the possibility of an alternate scenario.
Advertisements for the RansomHub RaaS began in the cyber underground on February 2. They cited an encryptor written in the C++ and Go programming languages and offered adjustable encryption algorithms based on affiliate requirements. A new DLS showcasing the RansomHub brand accompanied the dark web advertisements.
The Knight ransomware source code was listed for sale on the underground RAMP forum on February 18, 2024.
The source code is believed to have been sold two days later, on February 20, to an unknown buyer.
RansomHub listed the first victim on its DLS on February 21, one day after the believed sale of the Knight ransomware source code.
While Arete cannot say for sure whether the threat actors behind RansomHub are the same as those behind Knight ransomware, we are certain that the RansomHub encryptor is based on the Knight ransomware source code. Considering the above timeline, the two most plausible hypotheses are that the actors behind Knight ransomware were waiting to sell their source code before officially launching the rebrand or that the actors behind RansomHub immediately began leveraging their recently purchased encryption capability to target victims in the wild.
Victimology
Since its emergence, RansomHub has targeted several high-profile targets and caused a broad impact across multiple sectors:
Frontier: RansomHub extorted telecom giant Frontier and threatened to release 750,000 social security numbers from its customer base.
Christie’s: RansomHub extorted the auction house for the wealthy with the threat of releasing data on 45,000 clients.
Change Healthcare: Following a data security incident, RansomHub attempted to sell PHI stolen from the healthcare giant on the dark web.
These incidents demonstrate that RansomHub doesn’t shy away from “big game hunting” or sensitive sectors amidst the recent wave of law enforcement actions against ransomware groups. They also showcase that the group is opportunistic when it comes to monetizing its efforts. Most ransomware groups will not invest the time or effort to sell data on the dark web in favor of simply demanding ransoms from their victims. However, RansomHub took the approach of selling the allegedly stolen data from Change Healthcare.
Should the actors behind RansomHub prove to be the same as those behind Knight ransomware, it should be noted that Knight’s tenure in cybercrime was short lived, as the group was only active for seven months before the source code was listed for sale on RAMP forums.
While not certain, the intent of a hasty exit and rebrand could explain the motivation behind the group’s bold targeting of victims.
Analyst Comments
Regardless of the threat actors behind the operation or how long the group will remain active, RansomHub is currently one of the most prolific cybercrime groups active in the threat landscape. The group has targeted a wide range of high-profile victims in its short tenure thus far, and the actors are clearly not afraid to monetize their efforts in any way possible. Arete will continue monitoring for any change of tactics, dark web chatter, or the indication of a possible rebrand for the group.
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Article
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



