Clearlog

Overview

HackTool:Win32/Clearlog is a critical **Heuristic Detection** specifically designed to flag executables, scripts, or command-line activity attempting to wipe the Windows Security, Application, or System Event Logs. This is not a specific malware family, but a detection of a core Defense Evasion tactic (`T1070.001`). Legitimate system administrators rarely clear security logs; therefore, this action is almost exclusively associated with attackers or advanced malware attempting to erase forensic evidence of a breach.

Understanding Clearlog (Defense Evasion)
To an end-user, this action is invisible. For a SOC analyst, a Clearlog alert is an absolute, 'hair-on-fire' emergency. It means an attacker has not only compromised the system but has achieved administrative privileges (required to clear security logs) and is actively trying to hide their lateral movement, privilege escalation, or exfiltration activities.

Execution and Evasion Mechanics
Attackers trigger this detection by using built-in Windows utilities (Living off the Land) or custom scripts. Common methods include executing `wevtutil cl System` or `wevtutil cl Security` from a command prompt (`T1059.003`), using the PowerShell cmdlet `Clear-EventLog`, or utilizing WMI methods. Sophisticated malware might interact directly with the Windows Event Log API to selectively delete specific records, though bulk clearing is more common. This action permanently destroys the local forensic trail of the attacker's initial access and subsequent actions.

Indicators of Compromise & Impact
The impact is the devastating loss of forensic visibility on the compromised endpoint. The primary IoC *is* the alert itself. Host-based IoCs include EDR telemetry logging the execution of `wevtutil.exe` with the `cl` (clear) flag. Paradoxically, the Windows Event Log generates a final event before being wiped: **Event ID 1102 (The audit log was cleared)**. The presence of this specific Event ID is the definitive indicator of a successful Clearlog action.

MITRE ATT&CK Techniques

Observed techniques used by this family, mapped to our technical analysis hubs and the official MITRE ATT&CK framework:

Tactical Mitigations

Based on the techniques used by this family, consider the following defensive strategies:

• T1059.001: Restrict execution of PowerShell. Enforce PowerShell Constrained Language Mode and Script Block Logging.
• T1059.003: Restrict execution of Windows Command Shell (cmd.exe) and block unauthorized batch scripts.

MITRE D3FEND™ Defensive Countermeasures

Defensive techniques mapped to counter the offensive tradecraft observed in this family (via the MITRE D3FEND matrix):

Tiered Detection Rules (Cisco CAIRN Model)

Modern threat detection requires multi-layered rule engineering. We classify detections into three operational tiers based on signal fidelity:

rule MALWARE_WIN_CLEARLOG_T1_ARTIFACT {
    meta:
        description = "Tier 1 Primitive Artifact: Raw string matches for Clearlog"
        tier = "T1 - Primitive Artifact"
        confidence = "Low-Medium (Fast Triage)"
        author = "SystemHelpdesk Threat Research Desk"
        date = "2026-10-14"
    strings:
        $s1 = "clearlog" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

title: SystemHelpDesk Detection - Clearlog (Advanced Threat) Execution & Triage
id: 18a545fb-8c8d-5929-ae52-a7793c99c0f2
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
  with the Clearlog malware family. Detects proxy execution, reflective DLL loading,
  and remote command injection associated with modular enterprise backdoors.
references:
- https://malware-families-catalog.systemhelpdesk.com/families/clearlog
- https://malware-families-catalog.systemhelpdesk.com/defensive/backdoor-rat-protection
- https://malware-families-catalog.systemhelpdesk.com/
author: Ricky Jordan, Lead Threat Intelligence Analyst, SystemHelpDesk MSP
date: '2026-10-14'
modified: '2026-10-14'
tags:
- attack.advanced-threat
- author.ricky-jordan
- source.systemhelpdesk-mfc
- attack.t1059_003
- attack.t1059_001
- attack.t1070_001
logsource:
  category: process_creation
  product: windows
detection:
  selection_process:
    Image|endswith:
    - \powershell.exe
    - \cmd.exe
    - \rundll32.exe
    - \regsvr32.exe
    CommandLine|contains:
    - DownloadString
    - IEX(
    - '/s /n /u /i:'
    - sc create
    - start-process
  condition: selection_process
falsepositives:
- Legitimate enterprise administrative scripts during approved change windows
- Authorized IT software deployment utilities and backup management agents
level: high

rule MALWARE_WIN_CLEARLOG_T3_ATTRIBUTION {
    meta:
        description = "Tier 3 Attribution Fingerprint: Heuristic detection for Clearlog tradecraft"
        tier = "T3 - Attribution Fingerprint"
        confidence = "High (Confirmed Family Signature)"
        author = "SystemHelpdesk Threat Research Desk"
        date = "2026-10-14"
    strings:
        // Core family identifier & heuristic payload signatures
        $attrib_str = "clearlog" ascii wide nocase
        $pe_magic = "MZ" ascii
        $net_marker = "http" ascii nocase
    condition:
        uint16(0) == 0x5a4d and ($attrib_str and $net_marker) and filesize < 15MB
}

Containment & Response Steps

Ordered checklist for responders. Adapt to your environment and engage professional support for active incidents.

1. IMMEDIATELY isolate the endpoint from the network; the attacker possesses administrative privileges and is actively destroying evidence.
2. Preserve RAM immediately. Since the disk-based logs are destroyed, volatile memory is the only remaining source of forensic artifacts.
3. Correlate the timestamp of the log clearing with centralized SIEM logs (if logs are forwarded) to determine what actions occurred immediately prior to the wipe.
4. Initiate a major incident response protocol; assume the attacker has full administrative control and is likely moving laterally.

What to Avoid

Common mistakes during response to this family that can destroy evidence, spread the infection, or worsen recovery.

1. Do not reboot the machine; this will destroy the volatile memory (RAM), which is critical now that the disk logs are gone.
2. Avoid assuming the attack was a failure just because evidence is missing; log clearing is the hallmark of a successful, professional intrusion.

References & External Analysis

• Search "clearlog" on VirusTotal (External Analysis)
• Search "clearlog" on Any.Run (Sandbox Sandbox)
• Search "clearlog" on MalwareBazaar (Malware Samples)

Frequently Asked Questions

Related Threats (Category: Advanced Threat)

Explore other documented threats in the same operational category:

• Oneinstaller
• Revizer
• Onlineg
• Gamium
• Equationdrug
• Ssprotect
• Searchsetter
• Speed

Machine-readable

Get this profile as JSON: https://malware-families-catalog.systemhelpdesk.com/api/clearlog.json

Ecosystem & Interactive Environments

This profile is part of the Malware Families Catalog, a public dataset of 2,899 malware families. The catalog is also published across our ecosystem: Hugging Face, Kaggle, Zenodo, Replit, StackBlitz, CodeSandbox, and CodePen.