Sigma detection rules, expert-reviewed

TAG-144 Dynamic DNS C2 Resolution via Structured DuckDNS Subdomain (via dns_query)

This rule detects DNS resolution of TAG-144 command-and-control hosts using the campaign envio dynamic-DNS naming scheme on duckdns.org, matching the structured envio prefix with a short numeric suffix. Adversaries leverage dynamic DNS to rotate resilient C2 endpoints, making the specific subdomain pattern a useful command-and-control indicator.

Malicious Bad Apples Data Exfiltration via snmptrap OID

This rule detects snmptrap sending data to the attacker-specific enterprise OID 1.3.6.1.4.1.99999, matching the Bad Apples abuse of native macOS SNMP tooling to smuggle collected data out over an alternate protocol. Encoding stolen information inside SNMP trap fields evades controls focused on HTTP and DNS exfiltration. Use of this fabricated OID with snmptrap indicates covert exfiltration.

Suspicious WScript Executing VBScript from Masqueraded File Extension

This rule detects wscript.exe running a VBScript engine against files with non-script extensions such as drv, regtrans-ms or ntuser.dat, an execution and masquerading technique used by Shuckworm to hide its GammaSteel loader.

Obfuscated ELF Magic-Byte Restoration via dd conv notrunc in Sindoor Dropper Chain (via process_creation)

This rule detects use of dd with conv=notrunc to overwrite the first bytes of a file, the ELF magic-byte restoration trick used by the Sindoor Dropper to reassemble a runnable Linux payload from a header-stripped file. Adversaries leverage this to defeat static detection of the staged binary, making detection useful for catching the deobfuscation step of the infection chain.

Suspicious systemd User Service Persistence miasma-monitor (via file_event)

This rule detects creation of a miasma-monitor systemd user service unit used by the M-Red-Team AsyncAPI compromise for persistence. Writing a user-level systemd service lets an attacker relaunch a monitoring implant on login without root. The specific unit name combined with the user systemd path is a strong persistence signal.

Masquerading Firewall Allow Rule Masquerading as Windows Defender Update Service via Netsh (via process_creation)

This rule detects netsh adding an advfirewall rule named to impersonate a Windows Defender update service, a defense-evasion step in the Salat Stealer chain that whitelists its own network traffic. Adversaries leverage a benign-looking firewall rule name to allow C2 and exfiltration traffic while blending into legitimate configuration, so this behavior warrants review alongside surrounding activity.

Web Server Worker Process Spawning Command Interpreter

This rule detects the IIS worker process w3wp.exe spawning command shells or administrative utilities, behavior consistent with the China Chopper web shell used in Operation Soft Cell against telecommunications providers. A web server worker launching cmd, wmic or PowerShell strongly indicates web shell command execution.

Malicious Akira Ransomware Encryption Execution (via process_creation)

This rule detects the Akira ransomware encryptor invoked with its characteristic path and share targeting switches. These combined command-line flags drive selective encryption across local and network locations. Detection here indicates active encryption and imminent impact on the environment.

Malicious PowerShell AMSI Bypass via AmsiInitFailed Command Line

This rule detects the amsiInitFailed AMSI-bypass string in a PowerShell command line, a defense-evasion technique used after Citrix Bleed exploitation to disable script scanning before running the LockBit toolkit. Setting amsiInitFailed forces AMSI to skip inspection. Detecting the string exposes an active attempt to blind endpoint script scanning.

Malicious Tunneling Tool Execution on Linux Host (via process_creation)

This rule detects execution of known network tunneling and proxy utilities used to pivot and exfiltrate from compromised Linux and container hosts. Observed in the Elastic Security Labs TeamPCP scenario where gost, frps, chisel, and socat establish covert channels for command and control and lateral movement.

Malicious DLL Side-Loading via AVGApplicationFrameHost

This rule detects the AVGApplicationFrameHost.exe binary loading a wsc.dll module, a DLL side-loading chain used by TheWizards APT group to execute the WizardNet backdoor alongside an encrypted log.dat shellcode payload. Abusing a signed AV-related host process to load an attacker DLL evades trust controls and blends malicious execution into legitimate software.

Suspicious PowerShell Self-Delete Of Executable via Process Creation

This rule detects PowerShell used to delete an executable in a wait-and-retry loop. Rhysida ransomware removes its own binary after execution using a PowerShell routine that loops on Test-Path and Start-Sleep until the file is gone, eliminating forensic artifacts.

Suspicious Script Host Execution of JavaScript From a User-Writable Directory (via process_creation)

This rule detects wscript.exe or cscript.exe running a .js or .jse file from a user-writable location such as AppData or Temp, the delivery-and-execution pattern behind JavaScript loaders like Gootloader that arrive through SEO-poisoned downloads. Malicious script-host execution from user directories is a recurring initial-access and execution behavior in the Red Canary Threat Detection Report. Detecting it surfaces the loader stage before it fetches and runs a second-stage payload.

Suspicious Remote Script Downloaded via curl and Piped to Shell (via process_creation)

This rule detects a curl download piped directly into a shell in a single command line, the download-and-execute pattern used by the updated XCSSET malware to retrieve and run stage payloads from attacker infrastructure. Adversaries chain curl into sh to fetch and execute code without writing a script to disk, so this one-liner is a strong indicator of remote payload execution on macOS.

Suspicious File Download to tmp and Quarantine Removal via curl and xattr

This rule detects a shell command that downloads a file into the tmp directory with curl, strips the macOS quarantine attribute with xattr, marks it executable and runs it. This chain is the macOS infection path from fake Claude Code advertisements delivering an AMOS style stealer.