PUA - NimScan Execution

Detects usage of NimScan, a portscanner utility. In early 2025, adversaries were observed using this utility to scan for open ports on remote hosts in a compromised environment. This rule identifies the execution of NimScan based on the process image name and specific hash values associated with different versions of the tool.

title: PUA - NimScan Execution
id: 4fd6b1c7-19b8-4488-97f6-00f0924991a3
status: test
description: |
    Detects usage of NimScan, a portscanner utility.
    In early 2025, adversaries were observed using this utility to scan for open ports on remote hosts in a compromised environment.
    This rule identifies the execution of NimScan based on the process image name and specific hash values associated with different versions of the tool.
references:
    - https://x.com/cyberfeeddigest/status/1887041526397587859
    - https://github.com/elddy/NimScan
author: Swachchhanda Shrawan Poudel (Nextron Systems)
date: 2025-02-05
tags:
    - attack.discovery
    - attack.t1046
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        - Image|endswith: '\NimScan.exe' # Other metadata fields such as originalfilename and product were omitted because they were null
        - Hashes|contains:
              - 'IMPHASH=41BB1C7571B3A724EB83A1D2B96DBB8C' # v1.0.8
              - 'IMPHASH=B1B6ADACB172795480179EFD18A29549' # v1.0.6
              - 'IMPHASH=0D1F896DC7642AD8384F9042F30279C2' # v1.0.4 and v1.0.2
    condition: selection
falsepositives:
    - Legitimate administrator activity
level: medium

• T1046Network Service Discovery

• https://x.com/cyberfeeddigest/status/1887041526397587859↗
• https://github.com/elddy/NimScan↗