Suspicious PUA - NimScan Execution (via process_creation)

This rule detects use of NimScan, a portscanner utility. In early 2025, threat actors were observed using this utility to scan for open ports on remote hosts in a compromised environment. This rule flags the execution of NimScan based on the process image name and specific hash values linked with different versions of the tool.

SigmamediumWindowsv1

sigma

suspicious-pua-nimscan-execution-via-process-creation

title: Suspicious PUA - NimScan Execution (via process_creation)
id: 044759ba-5e91-5cfe-be6b-59b551729b46
status: stable
description: This rule detects use of NimScan, a portscanner utility. In early 2025, threat actors were observed using this utility to scan for open ports on remote hosts in a compromised environment. This rule flags the execution of NimScan based on the process image name and specific hash values linked with different versions of the tool.
references:
    - https://attack.mitre.org/techniques/T1046/
    - https://x.com/cyberfeeddigest/status/1887041526397587859
    - https://github.com/elddy/NimScan
author: Huntrule Team
date: 2026-04-03
tags:
    - attack.discovery
    - attack.t1046
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        - Image|endswith: '\NimScan.exe'
        - Hashes|contains:
              - 'IMPHASH=41BB1C7571B3A724EB83A1D2B96DBB8C'
              - 'IMPHASH=B1B6ADACB172795480179EFD18A29549'
              - 'IMPHASH=0D1F896DC7642AD8384F9042F30279C2'
    condition: selection
falsepositives:
    - Unknown
level: medium

Known false positives

Unknown

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.