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Detection rules › Sigma

Communication To Uncommon Destination Ports

Status
test
Severity
medium
Log source
category network_connection, product windows
Author
Florian Roth (Nextron Systems)
Source
github.com/SigmaHQ/sigma

Detects programs that connect to uncommon destination ports

MITRE ATT&CK coverage

TacticTechniques
Command & Control

Telemetry coverage

ProviderRecord / event type
SysmonEvent ID 3: Network connection

Rule body

title: Communication To Uncommon Destination Ports
id: 6d8c3d20-a5e1-494f-8412-4571d716cf5c
related:
    - id: 4b89abaa-99fe-4232-afdd-8f9aa4d20382
      type: similar
status: test
description: Detects programs that connect to uncommon destination ports
references:
    - https://docs.google.com/spreadsheets/d/17pSTDNpa0sf6pHeRhusvWG6rThciE8CsXTSlDUAZDyo
author: Florian Roth (Nextron Systems)
date: 2017-03-19
modified: 2024-03-12
tags:
    - attack.persistence
    - attack.command-and-control
    - attack.t1571
logsource:
    category: network_connection
    product: windows
detection:
    selection:
        Initiated: 'true'
        DestinationPort:
            - 8080
            - 8888
    filter_main_local_ranges:
        DestinationIp|cidr:
            - '127.0.0.0/8'
            - '10.0.0.0/8'
            - '172.16.0.0/12'
            - '192.168.0.0/16'
            - '169.254.0.0/16'
            - '::1/128'  # IPv6 loopback
            - 'fe80::/10'  # IPv6 link-local addresses
            - 'fc00::/7'  # IPv6 private addresses
    filter_optional_sys_directories:
        Image|startswith:
            - 'C:\Program Files\'
            - 'C:\Program Files (x86)\'
    condition: selection and not 1 of filter_main_* and not 1 of filter_optional_*
falsepositives:
    - Unknown
level: medium

Stages and Predicates

Stage 0: condition

selection and not 1 of filter_main_* and not 1 of filter_optional_*

Stage 1: selection

selection:
    Initiated: 'true'
    DestinationPort:
        - 8080
        - 8888

Stage 2: not filter_main_local_ranges

filter_main_local_ranges:
    DestinationIp|cidr:
        - '127.0.0.0/8'
        - '10.0.0.0/8'
        - '172.16.0.0/12'
        - '192.168.0.0/16'
        - '169.254.0.0/16'
        - '::1/128'
        - 'fe80::/10'
        - 'fc00::/7'

Stage 3: not filter_optional_sys_directories

filter_optional_sys_directories:
    Image|startswith:
        - 'C:\Program Files\'
        - 'C:\Program Files (x86)\'

Exclusions

The rule actively suppresses these predicates.

FieldKindExcluded valuesSearch
DestinationIpcidr_match10.0.0.0/8excludes:DestinationIp field:"DestinationIp" value:"10.0.0.0/8"
DestinationIpcidr_match127.0.0.0/8excludes:DestinationIp field:"DestinationIp" value:"127.0.0.0/8"
DestinationIpcidr_match169.254.0.0/16excludes:DestinationIp field:"DestinationIp" value:"169.254.0.0/16"
DestinationIpcidr_match172.16.0.0/12excludes:DestinationIp field:"DestinationIp" value:"172.16.0.0/12"
DestinationIpcidr_match192.168.0.0/16excludes:DestinationIp field:"DestinationIp" value:"192.168.0.0/16"
DestinationIpcidr_match::1/128excludes:DestinationIp field:"DestinationIp" value:"::1/128"
DestinationIpcidr_matchfc00::/7excludes:DestinationIp field:"DestinationIp" value:"fc00::/7"
DestinationIpcidr_matchfe80::/10excludes:DestinationIp field:"DestinationIp" value:"fe80::/10"
Imagestarts_withC:\Program Files (x86)\excludes:Image field:"Image" value:"C:\Program Files (x86)\"
Imagestarts_withC:\Program Files\excludes:Image field:"Image" value:"C:\Program Files\"

Indicators

These rows show field, operator, and value matches.

FieldKindValuesSearch
DestinationPorteq
  • 8080
  • 8888
field:"DestinationPort" kind:eq
Initiatedeq
  • true corpus 50 (sigma 50)
field:"Initiated" kind:eq value:"true"