Detection rules › Sigma
Office Application Initiated Network Connection Over Uncommon Ports
Detects an office suit application (Word, Excel, PowerPoint, Outlook) communicating to target systems over uncommon ports.
Known false positives
- Other ports can be used, apply additional filters accordingly
MITRE ATT&CK coverage
| Tactic | Techniques |
|---|---|
| Stealth | No specific technique |
| Command & Control | No specific technique |
Telemetry coverage
| Provider | Record / event type |
|---|---|
| Sysmon | Event ID 3: Network connection |
Rule body
title: Office Application Initiated Network Connection Over Uncommon Ports
id: 3b5ba899-9842-4bc2-acc2-12308498bf42
status: test
description: Detects an office suit application (Word, Excel, PowerPoint, Outlook) communicating to target systems over uncommon ports.
references:
- https://blogs.blackberry.com/en/2023/07/romcom-targets-ukraine-nato-membership-talks-at-nato-summit
author: X__Junior (Nextron Systems), Nasreddine Bencherchali (Nextron Systems)
date: 2023-07-12
modified: 2025-10-17
tags:
- attack.command-and-control
- attack.stealth
logsource:
category: network_connection
product: windows
detection:
selection:
Initiated: 'true'
Image|endswith:
- '\excel.exe'
- '\outlook.exe'
- '\powerpnt.exe'
- '\winword.exe'
- '\wordview.exe'
filter_main_common_ports:
DestinationPort:
- 53 # DNS
- 80 # HTTP
- 139 # NETBIOS
- 389 # LDAP
- 443 # HTTPS
- 445 # SMB
- 3268 # MSFT-GC
filter_main_outlook_ports:
Image|contains: ':\Program Files\Microsoft Office\'
Image|endswith: '\OUTLOOK.EXE'
DestinationPort:
- 143
- 465 # SMTP
- 587 # SMTP
- 993 # IMAP
- 995 # POP3
condition: selection and not 1 of filter_main_*
falsepositives:
- Other ports can be used, apply additional filters accordingly
level: medium
Stages and Predicates
Stage 0: condition
selection and not 1 of filter_main_*Stage 1: selection
selection:
Initiated: 'true'
Image|endswith:
- '\excel.exe'
- '\outlook.exe'
- '\powerpnt.exe'
- '\winword.exe'
- '\wordview.exe'
Stage 2: not filter_main_*
filter_main_common_ports:
DestinationPort:
- 53
- 80
- 139
- 389
- 443
- 445
- 3268
filter_main_outlook_ports:
Image|contains: ':\Program Files\Microsoft Office\'
Image|endswith: '\OUTLOOK.EXE'
DestinationPort:
- 143
- 465
- 587
- 993
- 995
Exclusions
The rule actively suppresses these predicates.
Indicators
These rows show field, operator, and value matches.
| Field | Kind | Values | Search |
|---|---|---|---|
Image | ends_with |
| field:"Image" kind:ends_with |
Initiated | eq |
| field:"Initiated" kind:eq value:"true" |