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 the 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.

Generated Detections (Boilerplate)

These YARA and Sigma rules are auto-generated based on the family name and aliases. They must be heavily tuned before deployment in a production environment.

YARA Rule

rule MALWARE_WIN_CLEARLOG {
    meta:
        description = "Detects Clearlog (advanced_threat)"
        author = "SystemHelpdesk Boilerplate Generator"
        date = "2026-07-06"
    strings:
        $s1 = "clearlog" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

Sigma Rule

title: Suspicious Clearlog Activity
id: 8cf9a232409b269fbc8605c044d20e35
status: experimental
description: Detects generic indicators of the clearlog malware family.
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith:
            - '\cmd.exe'
            - '\powershell.exe'
        CommandLine|contains:
            - "*clearlog*"
    condition: selection
level: medium

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)

Frequently Asked Questions

Related Families (Category: advanced_threat)

Explore other malware families in the same category:

• Keybase
• Flvdownloader
• Installm
• Pirminay
• Downloadassistant

Machine-readable

Get this profile as JSON: https://jordanricky1604-ship-it.github.io/malware-families-catalog/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.