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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Article
Anubis Utilizing Custom Backdoor and BYOVD Tools in Attacks
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
Article
Ransomware Trends & Data Insights: October 2026
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
Article
PHP2Shell Exploitation Update
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)
Article
LiteLLM Supply-Chain Compromise
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