Windows Network Connections Initiated by Notepad.exe

Alerts when notepad.exe initiates an outbound network connection, excluding typical printing traffic on port 9100.

FreeReviewedSigma · High · v2

Product: windows
Category: network_connection
Author: EagleEye Team (SigmaHQ), DRL 1.1
Published: 2020-05-14
Updated: 2026-07-31

ATT&CK techniques

Priv Esc → Defense Evasion

Recon
Resource Dev
Initial Access
Execution
Persistence
Priv Esc
- T1055Process Injection
Defense Evasion
- T1055Process Injection
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule flags network connections where the process creating the connection is identified as notepad.exe. Unexpected outbound activity from Notepad can indicate suspicious staging or abuse of a legitimate binary by an attacker. The detection relies on Windows network connection telemetry that includes the connecting process image path and destination port information to suppress common printing-related cases.

Reporting behind it

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Windows Network Connections Initiated by Notepad.exe

Pivot detection · T1055 · 9 related

Changelog

v2
Candidate ingested via manual entry.2026-07-31
v1
No changelog recorded for this version.2026-07-30

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

windows-network-connections-initiated-by-notepad-exe-e81528db

title: Windows Network Connections Initiated by Notepad.exe
id: ef224332-8b56-4613-886e-8b61c54559dd
status: test
description: This rule flags network connections where the process creating the connection is identified as notepad.exe. Unexpected outbound activity from Notepad can indicate suspicious staging or abuse of a legitimate binary by an attacker. The detection relies on Windows network connection telemetry that includes the connecting process image path and destination port information to suppress common printing-related cases.
references:
  - https://web.archive.org/web/20200219102749/https://www.sans.org/cyber-security-summit/archives/file/summit-archive-1492186586.pdf
  - https://www.cobaltstrike.com/blog/why-is-notepad-exe-connecting-to-the-internet
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/network_connection/net_connection_win_notepad.yml
author: EagleEye Team, Huntrule Team
date: 2020-05-14
modified: 2024-02-02
tags:
  - attack.privilege-escalation
  - attack.command-and-control
  - attack.execution
  - attack.stealth
  - attack.t1055
logsource:
  category: network_connection
  product: windows
detection:
  selection:
    Image|endswith: \notepad.exe
  filter_optional_printing:
    DestinationPort: 9100
  condition: selection and not 1 of filter_optional_*
falsepositives:
  - Printing documents via notepad might cause communication with the printer via port 9100 or similar.
level: high
license: DRL-1.1
related:
  - id: e81528db-fc02-45e8-8e98-4e84aba1f10b
    type: derived

Convert

This rule as a query you can run. Uses no unlock credit.

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