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Conti Ransomware is the New Ryuk?

Arete Analysis

Summary 

Arete’s Threat Intelligence team observed that Conti ransomware could be a rebrand of Ryuk ransomware, as both variants use similar tactics to deploy ransomware executables. 

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Background 

Based on analysis of Conti ransomware, which was originally spotted in the wild in February of this year, the Arete Threat Intelligence team believes that this variant is being operated by the same group that conducted Ryuk ransomware attacks in the past. Digital forensics analysis of systems impacted by Conti ransomware revealed that it is generally being deployed by the attackers using the TrickBot banking trojan. Since early 2019, Ryuk ransomware operators exclusively used TrickBot trojan in their operations. In the 1st quarter of 2020, the number of Ryuk ransomware attacks significantly declined while the number of new Conti matters started to rise, which is a secondary indicator of a connection between both variants. 

Conti Overview

Conti is a sophisticated ransomware variant that emerged in February 2020. Unlike most of its’ peers, Conti ransomware encrypts files on victims’ machines significantly faster by running 32 concurrent threads and utilizing all computing power that impacted systems have available. As a result of that, devices with multi-core CPUs get encrypted quicker. Conti has the capability to encrypt local hard drives, network shares and other devices on the local network. To encrypt the data, Conti uses the AES-256 encryption key, which is bundled with the RAS-4096 public encryption key (Note: this key is unique for each victim). Since the encryption key is unique for each victim, Conti operators cannot provide a decryption tool, which would work only on specific devices. The Conti decryption tool works on all encrypted systems within a victim’s networks. 

Prior to the start of the encryption, Conti leverages Windows Restart Manager to disable security, backups and other applications that may keep files locked on the impacted systems. Then it deletes Shadow Volume copies to make it impossible to use built-in Windows volume backups to restore data after the encryption. 

Once encryption completes, the .CONTI extension is added to all encrypted files and the ransom note, CONTI_README.txt, is placed in each folder. Each ransom note contains 2 email addresses to get in touch with the attackers, which are unique for each victim. This method is consistent with what Ryuk operators used in their attacks. Conti operators use a unique set of emails to identify each victim, so it does not matter if a victim responds from a corporate account or from a public email account – attackers still will know which victim they are communicating with. Just like Ryuk, Conti conducts research into information about their victims and sets ransom demands based on what they believe the victim can afford to pay. 

Conti Ransom Note

Figure 1 - % of Data Exfiltration in Ryuk matters

It was uncommon for Ryuk to exfiltrate data from victims’ systems. Based on Arete analysis of previous matters, we only observed data exfiltration in 7% of cases. Unlike Ryuk, it appears that Conti ransomware operators decided to join the bandwagon of other 20+ variants that steal data from victims’ environments prior to the encryption. Conti also created a web site where they publish lists of their victims in attempt to improve their chances of getting paid. In the last few weeks, Conti stepped up their extortion attempts and, in some cases, called the owner/managers of companies directly, to inform them that they have been compromised and threaten them to release the stolen data if they don’t pay. 

Security Recommendations

Below are a few recommendations that will help to protect your organization from Conti ransomware attacks: 

  1. Implement a sophisticated Endpoint Detection & Response (EDR) solution that will rely on behavior analysis, instead of just malware signatures, and have tamper-proof capabilities. 

  2. Keep your systems updated and disable SMBv1, to protect against Windows EternalBlue vulnerability, which is actively being used by the TrickBot banking trojan to propagate within a victims’ environment. 

  3. Block outbound traffic on your firewall for ports 447, 449 & 8082 (Note: along with 443 those ports are commonly used by TrickBot) and implement geo-blocking for foreign countries that you don’t have any employees in and don’t do business with.

  4. Continuously educate your users on how to identify suspicious phishing emails and attachments. 

  5. Implement an off-site backup solution and test it regularly 

Figure 2 - Screenshot of the Conti exfil site

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Red alert symbols and warning icons spreading across a digital network, representing firewall compromise and widespread cyber intrusion.
Red alert symbols and warning icons spreading across a digital network, representing firewall compromise and widespread cyber intrusion.

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