Cloudflare - Empty user agent

Status: available
Severity: medium
Time window: 1h
Source: github.com/Azure/Azure-Sentinel

'Detects requests where user agent is empty.'

MITRE ATT&CK coverage

Tactic	Techniques
Initial Access	`T1133` External Remote Services `T1190` Exploit Public-Facing Application

Rule body

id: 729c6d21-fad9-4a6a-9c7f-482393c95958
name: Cloudflare - Empty user agent
description: |
  'Detects requests where user agent is empty.'
severity: Medium
status: Available
requiredDataConnectors:
  - connectorId: CloudflareDataConnector
    dataTypes:
      - Cloudflare
queryFrequency: 1h
queryPeriod: 1h
triggerOperator: gt
triggerThreshold: 0
tactics:
  - InitialAccess
relevantTechniques:
  - T1190
  - T1133
query: |
  Cloudflare
  | where isempty(HttpUserAgentOriginal)
entityMappings:
  - entityType: IP
    fieldMappings:
      - identifier: Address
        columnName: SrcIpAddr
version: 1.0.1
kind: Scheduled

Stages and Predicates

Stage 1: `source`

Cloudflare

Stage 2: `where`

| where isempty(HttpUserAgentOriginal)

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`HttpUserAgentOriginal`	is_null	(no value, null check)	`field:"HttpUserAgentOriginal" kind:is_null`

Cloudflare - Empty user agent

MITRE ATT&CK coverage

Rule body

Stages and Predicates

Stage 1: source

Stage 2: where

Indicators

Stage 1: `source`

Stage 2: `where`