In October, researchers observed the Anubis ransomware group using a new custom backdoor named Lindnor, which masqueraded as a Chrome component and VMware file and sent the process ID, operating system version, file path, computer name, username, domain, and logon server to a command-and-control (C2) server. Threat actors dropped multiple executables to help terminate security services, along with five publicly known vulnerable drivers. They also installed the legitimate remote access tool AnyDesk and a separate tool to run it in Safe Mode, likely to maintain access when security software was not fully running.

Arete recently observed Anubis using similar tools and tactics, in particular Bring Your Own Vulnerable Driver (BYOVD) techniques and AnyDesk for remote access, alongside PowerShell-based loaders to support defense evasion, privilege escalation, and malicious payload execution.

Analyst Comments

The observed activity reflects an evolving, multi-stage intrusion approach focused on establishing persistent access, evading security controls, and enabling follow-on malicious activity. Notably, the deployment of custom backdoors such as Lindnor indicates a shift toward more tailored tooling designed to maintain covert access. BYOVD techniques and PowerShell-based loaders have also been observed facilitating defense evasion and ultimately executing malicious binary payloads. Collectively, these activities demonstrate increasingly sophisticated tradecraft focused on persistent access and circumventing endpoint security controls. 

Sources

• New Lindnor Backdoor and Glut of Security Killers Used in Ransomware Attack on U.S. Org

Although Akira once again emerged as the most active ransomware group in October, overall ransomware and extortion activity was not dominated by any single threat group and instead remained widely distributed among a variety of threat actors, continuing the trend that began around August. Arete identified 31 unique named threat groups in October, the most observed in a single month so far in 2026. In addition to Akira, Settra, and The Gentlemen were among the three most active groups. Several new threat actors also emerged, including BYOD, Kubera Team, QWCrypt, AoQin, Emperador, Osiris Team, and Cinder, with Cinder assessed as possibly part of a threat actor cluster affiliated with the former BlackFile group.

Figure 1. Activity from the top 10 threat groups in October 2026

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

• PHP2Shell emerged as one of the most significant threats in October, with increasing exploitation of the critical PHP vulnerabilities CVE-2026-109618 and CVE-2026-109619. Other notable vulnerabilities included CVE-2026-104286 affecting FortiMail, and CVE-2026-102255, a critical pre-authentication Server-Side Request Forgery (SSRF) vulnerability affecting SonicWall SMA1000 appliances, highlighting continued threat actor interest in internet-facing enterprise infrastructure.

• International law enforcement operations against cybercriminal groups continued to make headlines in October. German authorities announced the arrest of 28-year-old Russian national Vladimir K., suspected of being a senior operator within the Qilin Ransomware-as-a-Service (RaaS) group. Separately, the FBI arrested an individual with suspected links to ShinyHunters, adding to recent law enforcement activity targeting ransomware and extortion groups, including the disruption of KillSec. While Vladimir K.’s arrest has not yet had a notable impact on Qilin’s operational activity, it could provide law enforcement with greater insight into the group’s infrastructure and affiliate network, potentially supporting further disruption efforts.

• In early October, “The Luna Moth Files” exposed several files containing alleged internal communications associated with Luna Moth, also known as Silent Ransom Group, revealing insights into the group’s social engineering, data extortion, and victim negotiation operations. However, several claims remain unverified, and the exposure has not notably disrupted the group’s activity thus far, as it was among the top threat actors Arete observed throughout the month.

Sources

• Arete Internal

PHP2Shell exploitation activity continues to increase globally, with threat actors targeting the critical PHP remote code execution (RCE) vulnerabilities CVE-2026-109618 and CVE-2026-109619. Researchers recently identified low-volume scanning targeting unpatched or partially mitigated hosts across multiple countries and sectors, and the activity is assessed with moderate confidence as linked to a Korean-speaking operator associated with the Lazarus Group ecosystem. While PHP2Shell (CVE-2026-109618 and CVE-2026-109619) has been patched in PHP 8.5.12, 8.4.27, 8.3.36, and 8.2.35, the separately identified CVE-2026-115560 remains unpatched. 

What’s Notable and Unique

• PHP2Shell vulnerabilities can cause memory corruption due to improper error handling, potentially allowing threat actors to achieve remote code execution on vulnerable PHP servers.
  
  

• Observed activity includes mass scanning, PHP environment fingerprinting, exploitation attempts, credential and secret theft attempts, and attempts to deliver second-stage payloads and malware.
  
  

• Successful in-the-wild exploitation has also been reported against honeypots, resulting in shell command execution and the retrieval of additional payloads, demonstrating the potential for follow-on malicious activity.

Mitigations

Organizations should prioritize upgrading internet-facing PHP deployments to patched versions, migrating unsupported PHP versions, updating embedded and containerized PHP runtimes, and implementing available Web Application Firewall (WAF) protections as a temporary defense-in-depth measure.

Analyst Comments

PHP2Shell poses a significant security concern due to its potential to enable unauthenticated remote code execution on vulnerable PHP servers. The progression from mass scanning and exploitation attempts to reports of successful command execution demonstrates the potential for these vulnerabilities to support initial access and subsequent malicious activity. Arete has been closely monitoring PHP2Shell exploitation activity and regularly reviewing and updating related indicators to support detection and blocking efforts. Given the potential for remote exploitation and follow-on activity, PHP2Shell represents a high-priority initial-access risk, emphasizing the importance of timely patching and remediation of affected PHP environments.  

Sources

• PHP shares mitigation for new RCE vulnerability with no patch 

• PHP2Shell Exploitation Attempts Continue Amid Suspected N. Korea Global Scanning Activity 

• PHP2Shell Exploit Attempts Hit Millions as Attackers Try to Deploy Mirai Malware 

• Advisory: PHP2Shell Vulnerabilities (CVE-2026-109618, CVE-2026-109619) 

A software supply-chain attack compromised the release pipeline of LiteLLM, a widely used open-source Python SDK and AI gateway. Attackers leveraged the compromised pipeline on October 21st to publish a malicious LiteLLM version through PyPI and associated Docker registries. The affected release, LiteLLM 1.107.0, contained malware designed to steal credentials, sensitive configuration data, private keys, browser information, and other secrets from compromised systems.

What’s Notable and Unique

• The incident is particularly significant because LiteLLM provides a common API for applications to interact with AI models from multiple providers. It is reported that the project had approximately 61,800 GitHub stars and 92 million monthly PyPI downloads.
  
  

• Rather than modifying the core LiteLLM application source code, the threat actors reportedly tampered with the installation package itself. The malware was designed for broad credential and information theft and encrypted the collected data before uploading it to the attacker's endpoint.
  
  

• The compromise went beyond one-time credential theft. A malicious Python component launched a detached loader that checked a GitHub-hosted pointer every hour and could download Python code from an external server for execution on the compromised machine. This provided threat actors with a mechanism for subsequent remote code execution.

Analyst Comments

Although the malicious packages were subsequently removed, simply uninstalling or deleting the affected LiteLLM package may not be sufficient, because malicious Python startup files or the detached loader could remain on the host. All exposed information should be rotated immediately, and infected systems should be isolated and rebuilt from clean backups. The most recent clean release prior to the attack, LiteLLM 1.106.2, is currently the suggested recovery version.

Sources

• LiteLLM release pipeline hacked to distribute info-stealer malware
  
  

• LiteLLM 1.107.0 Compromised: Python Startup Hooks Steal Cloud, AI, and Proxy Credentials
  
  

• The Collector Reaches Beyond Provider API Keys