Unusual Child Process of dns.exe

Status: test
Severity: high
Log source: category process_creation, product windows
Author: Tim Rauch, Elastic (idea)
Source: github.com/SigmaHQ/sigma

Detects an unexpected process spawning from dns.exe which may indicate activity related to remote code execution or other forms of exploitation as seen in CVE-2020-1350 (SigRed)

MITRE ATT&CK coverage

Tactic	Techniques
Initial Access	`T1133` External Remote Services
Persistence	`T1133` External Remote Services

Telemetry coverage

Provider	Record / event type
Sysmon	Event ID 1: Process creation
Security-Auditing	Event ID 4688: A new process has been created.

Rule body

title: Unusual Child Process of dns.exe
id: a4e3d776-f12e-42c2-8510-9e6ed1f43ec3
status: test
description: Detects an unexpected process spawning from dns.exe which may indicate activity related to remote code execution or other forms of exploitation as seen in CVE-2020-1350 (SigRed)
references:
    - https://www.elastic.co/guide/en/security/current/unusual-child-process-of-dns-exe.html
author: Tim Rauch, Elastic (idea)
date: 2022-09-27
modified: 2023-02-05
tags:
    - attack.persistence
    - attack.initial-access
    - attack.t1133
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        ParentImage|endswith: '\dns.exe'
    filter:
        Image|endswith: '\conhost.exe'
    condition: selection and not filter
falsepositives:
    - Unknown
level: high

Stages and Predicates

Stage 0: `condition`

selection and not filter

Stage 1: `selection`

selection:
    ParentImage|endswith: '\dns.exe'

Stage 2: `not filter`

filter:
    Image|endswith: '\conhost.exe'

Exclusions

The rule actively suppresses these predicates.

Field	Kind	Excluded values	Search
`Image`	ends_with	`\conhost.exe`	`excludes:Image` `field:"Image" value:"\conhost.exe"`

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`ParentImage`	ends_with	`\dns.exe`	`field:"ParentImage" kind:ends_with value:"\dns.exe"`