Warlock Ransomware Exploiting SharePoint Flaws to Attack Water and Telecom Operators

A China-nexus threat actor is continuing to exploit Microsoft SharePoint Server vulnerabilities to deploy Warlock ransomware, with recent attacks striking essential-service and public-sector organizations across Portuguese- and Spanish-speaking countries.

Symantec tracks the operator as Longlegs, while Microsoft uses Storm-2603; earlier activity has also been linked to CL-CRI-1040, CamoFei, and ChamelGang.

During the past two months, the campaign compromised at least four organizations: a water utility, a telecommunications provider, a regional government body, and a university spanning Europe, Africa, and Latin America.

Warlock Ransomware Exploiting SharePoint Flaws

Warlock surfaced in June 2025 and quickly gained attention after being deployed through the SharePoint “ToolShell” exploit chain. ToolShell combined CVE-2025-49704 and CVE-2025-49706, while subsequent bypasses were assigned CVE-2025-53770 and CVE-2025-53771.

CISA confirmed that the chain enabled unauthorized access to on-premises SharePoint servers, exposure of internal configurations, and remote code execution.

Warlock was among the ransomware payloads observed on compromised systems. Newer SharePoint flaws disclosed in 2026 have kept the attack surface relevant, with CISA warning of active exploitation affecting supported on-premises editions.

According to research published by Symantec, Longlegs typically plants an ASPX webshell in SharePoint’s LAYOUTS directory, targeting several product versions simultaneously.

The webshell extracts ASP.NET machine keys, allowing the attackers to forge signed __VIEWSTATE payloads and execute code inside the SharePoint application pool.

Follow-on malware is then loaded through DLL sideloading, while installers are retrieved from legitimate hosting services, including Catbox and Wasabi, helping malicious traffic resemble routine cloud activity.

In one critical-infrastructure intrusion, activity began on July 22, 2026, when a webshell appeared on a SharePoint server. The attackers later ran whoami, net user /domain, and nltest /domain_trusts, deployed sideloading pairs, and used NetExec for Active Directory discovery, credential spraying, and remote execution.

They also installed Microsoft-signed code-insiders.exe as a service and abused Visual Studio Code’s tunnel function, creating covert access through infrastructure that defenders may associate with legitimate administrators or developers.

Before encryption, Longlegs pushed an AV and EDR termination utility to at least 40 hosts in roughly two hours. Recent operations have used the signed but vulnerable K7RKScan driver, tracked as CVE-2025-1055, to terminate privileged processes from kernel space a bring-your-own-vulnerable-driver technique.

NIST says the flaw stems from missing authorization in the driver’s IOCTL handler and affects K7 Security Anti-Malware versions earlier than 23.0.0.10. Investigators cautioned that they did not conclusively identify the specific driver used in this intrusion.

Warlock followed almost immediately on at least 33 systems. The attackers placed run.exe, rune.exe, and the ransom note “how to restore your files.txt” in the compromised domain’s SYSVOL share.

Because SYSVOL replicates across domain controllers and is readable domain-wide, ordinary Distributed File System Replication helped deliver the payload broadly, turning trusted Active Directory infrastructure into a ransomware distribution channel.

The campaign shows why patching alone is insufficient after suspected SharePoint exploitation. Defenders should hunt for webshells and abnormal SharePoint worker-process behavior, rotate ASP.NET and IIS machine keys after removing persistence, enable AMSI in Full Mode, deploy EDR, restrict SharePoint’s internet exposure, and inspect suspicious ToolPane.aspx requests.

CISA additionally recommends placing any necessary public-facing deployment behind an authenticated Layer 7 proxy and blocking external access to Central Administration. For water, telecom, government, and education operators, delayed remediation can transform one exposed collaboration server into domain-wide operational disruption.

The targeting pattern may reflect vulnerable exposed servers or deliberate regional tasking, but either explanation demands urgent asset discovery, containment, and recovery planning now.

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