Article
Windows Native Ransomware – Encrypting with Bitlocker
Arete Analysis
Threat Actors
Bitlocker is a native windows application intended to secure data through full volume encryption. However, threat actors have leveraged the capability to encrypt files before demanding a ransom payment for decryption. While this is not a novel concept, the question arises of why an actor would use this capability when so many ransomware encryptors are readily available with more advanced capabilities, and exactly what an actor would have to gain by using Bitlocker over another encryption capability. Even though not a novel concept, Bitlocker is still being used as the primary encryption capability for emerging actors such as the recently identified actor dubbed “Shrinklocker.”
Bitlocker Pros
Bitlocker has the inherent benefit of being a native windows application. By utilizing living off the land techniques, such as encrypting files using Bitlocker, the malicious activity is less likely to be detected by EDR tools.
Assuming Bitlocker is enabled within the environment the threat actor doesn’t have to join a ransomware-as-a-service (RaaS) program, seek out a leaked ransomware builder, or attempt to create their own encryption capability.
The use of Bitlocker to encrypt an environment often offers an additional layer of anonymity versus using an encryptor associated with an existing ransomware operation.
Bitlocker Cons
While it would be easy to assume that utilizing an existing tool within the environment for encryption may be easier than deploying a custom encryptor, that is not always the case. For an actor to encrypt an environment with Bitlocker it often requires an in-depth knowledge of the Windows operating system.
While Bitlocker certainly has the ability to encrypt files, many ransomware encryptors have additional capabilities that lead to increased chances of the victim paying the ransom. Often times, as victims consider whether to pay a ransom, they look at what data was encrypted, and what the associated business impact is. If the actor doesn’t effectively encrypt important files within the environment, they will be less likely to receive payment for their efforts.
Bitlocker – A Use Case
A recurring theme in ransomware incidents involving Bitlocker is the threat actor attempting to masquerade as well-known ransomware groups to add credibility to their operation, and in turn increase their chances of the victim paying the ransom. Often claiming to be whichever threat actor is dominating the news cycle, Arete has observed unidentified actors claiming to be ALPHV/BlackCat on several occasions. These tactics employed by cybercriminals place additional importance on threat analysis and the attribution process. Ransomware incidents should not be taken at surface level by simply looking at a ransom note and attributing the incident to the proclaimed ransomware. A process of malware analysis, identification of tactics, techniques, and procedures (TTPs), negotiation analysis, and other analytical observations should be undertaken and cross-referenced with historical data to build as accurate of an assessment as possible.
Analyst Comments
While not a new capability, threat actors continue to employ Bitlocker as an encryption alternative to proprietary encryptors. The ability for actors to encrypt files with a native application continues to be an interesting prospect as they attempt to evade antivirus and EDR software. However, as many organizations continue to mature their cybersecurity programs, they are able to detect the use of Bitlocker with their endpoint detection mechanisms. This forces threat actors hoping to use Bitlocker for encryption to learn new ways to obfuscate their actions, thus increasing the level of sophistication required to successfully navigate the everchanging blue team tactics.
Sources
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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