Detection rules › Kusto
NGINX - Multiple user agents for single source
'Detects requests with different user agents from one source in short timeframe.'
MITRE ATT&CK coverage
| Tactic | Techniques |
|---|---|
| Initial Access |
Rule body
id: 83a0b48f-1cb7-4b4f-a018-23c3203a239b
name: NGINX - Multiple user agents for single source
description: |
'Detects requests with different user agents from one source in short timeframe.'
severity: Medium
status: Available
requiredDataConnectors:
- connectorId: CustomLogsAma
dataTypes:
- NGINX_CL
queryFrequency: 1h
queryPeriod: 1h
triggerOperator: gt
triggerThreshold: 0
tactics:
- InitialAccess
relevantTechniques:
- T1190
- T1133
query: |
let threshold = 5;
NGINXHTTPServer
| summarize makeset(HttpUserAgentOriginal) by SrcIpAddr, bin(TimeGenerated, 5m)
| extend ua_count = array_length(set_HttpUserAgentOriginal)
| where ua_count > threshold
| extend IPCustomEntity = SrcIpAddr
entityMappings:
- entityType: IP
fieldMappings:
- identifier: Address
columnName: IPCustomEntity
version: 1.0.2
kind: Scheduled
Stages and Predicates
Parameters
let threshold = 5;
Stage 1: source
NGINXHTTPServer
Stage 2: summarize
| summarize makeset(HttpUserAgentOriginal) by SrcIpAddr, bin(TimeGenerated, 5m)
Stage 3: extend
| extend ua_count = array_length(set_HttpUserAgentOriginal)
Stage 4: where
| where ua_count > threshold
Stage 5: extend
| extend IPCustomEntity = SrcIpAddr
Indicators
These rows show field, operator, and value matches.
| Field | Kind | Values | Search |
|---|---|---|---|
ua_count | gt |
| field:"ua_count" kind:gt value:"5" |
Output fields
These fields are emitted when the rule matches.
| Field | Source |
|---|---|
SrcIpAddr | summarize |
ua_count | extend |
IPCustomEntity | extend |