Detection rules › Kusto
Excessive Failed Authentication from Invalid Inputs
'Creates an incident in the event that a user generates an excessive amount of failed authentications due to invalid inputs, indications of a potential brute force.'
MITRE ATT&CK coverage
| Tactic | Techniques |
|---|---|
| Credential Access | T1110 Brute Force |
Rule body kusto
id: c775a46b-21b1-46d7-afa6-37e3e577a27b
name: Excessive Failed Authentication from Invalid Inputs
description: |
'Creates an incident in the event that a user generates an excessive amount of failed authentications due to invalid inputs, indications of a potential brute force.'
severity: Medium
requiredDataConnectors:
- connectorId: SyslogAma
datatypes:
- Syslog
queryFrequency: 1h
queryPeriod: 1h
triggerOperator: gt
triggerThreshold: 0
tactics:
- CredentialAccess
relevantTechniques:
- T1110
query: |
let threshold = 15;
SymantecVIP
| where isnotempty(RADIUSAuth)
| where RADIUSAuth =~ "Reject"
| summarize Total = count() by bin(TimeGenerated, 15m), User, ClientIP
| where Total > threshold
entityMappings:
- entityType: Account
fieldMappings:
- identifier: FullName
columnName: User
- entityType: IP
fieldMappings:
- identifier: Address
columnName: ClientIP
version: 1.0.4
status: Available
kind: Scheduled
Stages and Predicates
Parameters
let threshold = 15;
Stage 1: source
SymantecVIP
Stage 2: where
| where isnotempty(RADIUSAuth)
Stage 3: where
| where RADIUSAuth =~ "Reject"
Stage 4: summarize
| summarize Total = count() by bin(TimeGenerated, 15m), User, ClientIP
Stage 5: where
| where Total > threshold
Indicators
Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.
| Field | Kind | Values |
|---|---|---|
RADIUSAuth | eq |
|
RADIUSAuth | is_not_null | |
Total | gt |
|
Output fields
Fields the rule emits when it matches. Chronicle authors list these in the outcome block; they appear on the detection and $risk_score drives alerting. Sentinel / Defender XDR rules build them up through project / summarize / extend stages. Sentinel maps these into alert fields via entityMappings and customDetails; Defender XDR custom detections surface them as alert fields directly.
| Field | Source |
|---|---|
ClientIP | summarize |
Total | summarize |
User | summarize |