Sigma detection rules, expert-reviewed

Malicious Windows Firewall Disable via Netsh

This rule detects netsh disabling the Windows firewall, removing host network restrictions to ease lateral movement and remote access. This was observed during KawaLocker ransomware deployment together with RDP enablement. Turning off the firewall exposes services and undermines network segmentation defenses.

Obfuscated Certutil Payload Download - Command (via process_creation)

This rule detects abuse certutil command to download obfuscated malicious payload.

Suspicious OpenSSH Reverse Tunnel Establishment via ssh.exe

This rule detects ssh.exe launched with the -R remote-forwarding switch to establish a reverse tunnel. In Talos IR ransomware engagements operators used OpenSSH reverse tunnels to proxy traffic back into the victim network for persistent access, so this is a protocol-tunneling indicator that should be correlated with the tunnel destination.

Suspicious TransferLoader Temporary File Creation in Windows Temp (via file_event)

This rule detects creation of the defender.user.tmp staging file in the Windows temporary directory that TransferLoader writes during execution. The masquerading filename mimics Microsoft Defender while residing in a temp path.

Suspicious SoftEther VPN Hamcore Config Written to ProgramData (via file_event)

This rule detects the creation of the SoftEther VPN hamcore.se2 archive or vpn_server.config under ProgramData as used by the Larva-26010 campaign to install a covert VPN tunnel on compromised web servers. These SoftEther artifacts in ProgramData indicate unauthorized remote access setup.

Suspicious TransferLoader Configuration Storage in Phone Config Registry Key (via registry_set)

This rule detects creation of registry values under the Windows Phone Config key that TransferLoader abuses to store its C2 server, sleep timeout, encryption key and in-memory PE payload. Legitimate software rarely writes rmi, to, id or md values under this path.

Suspicious Discovery Command Spawned by Java Process

This rule detects the Cleo Java runtime spawning Windows discovery utilities such as nltest, whoami, and ipconfig, the hands-on-keyboard reconnaissance seen after exploitation of Cleo file transfer software and the Malichus malware. A Java service process launching domain and host enumeration is not part of normal operation. This lineage indicates active post-exploitation of an internet-facing Cleo server.

Suspicious Persistence via pcalua Launching rundll32 Control_RunDLL

This rule detects the Program Compatibility Assistant pcalua being abused to launch rundll32 with the Control_RunDLL export against a user profile DLL. RedCurl uses this scheduled task chain to persist its BrowserSpec loader while masking the parent process.

Suspicious PowerShell Invoke-WebRequest Piped to Invoke-Expression via FakeBat Loader

This rule detects PowerShell downloading a remote payload with Invoke-WebRequest using a custom User-Agent and piping the response straight into Invoke-Expression. FakeBat, also tracked as EugenLoader, delivers this one liner through malvertising and fake software sites to stage its next component in memory. Fileless download and execute cradles like this bypass disk based controls and warrant investigation.

Malicious Lazarus SIGNBT DLL Side-Loading via PCHealthCheck Host (via image_load)

This rule detects the Microsoft PC Health Check binary PCHealthCheck.exe loading a PCHealthCheck.dll from outside standard program directories, the DLL side-loading technique the Lazarus SIGNBT cluster uses to execute malicious code under a signed utility. Restricting to non-program paths separates the abuse from the legitimately installed application.

Suspicious DLL Side-Loading from Non-Standard winsystem Directory

This rule detects a module being loaded from the non-standard C:\winsystem directory used by the STARKVEIL chain to stage side-loaded DLLs alongside a legitimate signed executable. Attackers rely on this masquerading path to run malicious code under a trusted process while evading directory-based allowlists.

ClickFix Pastejacking via Script Interpreter Command in Run Dialog MRU (via registry_set)

This rule detects ClickFix pastejacking where a clipboard-injected download-and-execute command is entered through the Windows Run dialog and recorded in the Explorer RunMRU key. Adversaries leverage the Run dialog to have the victim manually launch a script interpreter, so PowerShell or download utilities appearing in RunMRU history is a strong user-assisted execution indicator.

Suspicious browsercore Execution from Anomalous Parent for PRT Cookie (via process_creation)

This rule detects browsercore.exe launched by a process other than a known browser or task host, a pattern used to request a PRT cookie for cloud authentication abuse. The cloud lateral-movement research shows attackers invoke browsercore outside its normal browser context to obtain single sign-on artifacts. An unexpected parent for this binary is a heuristic sign of token theft.

Malicious DLL Sideloading via WSPrint and BugSplatRc64 by UAT-9244

This rule detects the WSPrint executable loading BugSplatRc64.dll from its ProgramData directory. UAT-9244 sideloads this DLL to execute follow-on implants under a benign-looking process. Loading a payload DLL from ProgramData through a planted executable is a hallmark of DLL search-order hijacking.

OpenSSH Server Firewall Configuration on Windows - Firewall (via firewall-as)

This rule detects configure the Windows firewall to allow incoming connections to perform stealthy lateral movement.