detection.wiki

Detection rules › Kusto

Silverfort - Log4Shell Incident

Severity
high
Time window
15m
Source
github.com/Azure/Azure-Sentinel

'Vulnerability allows attackers to execute arbitrary code on affected systems by exploiting a flaw in the way Log4j handles log messages containing specially crafted strings'

MITRE ATT&CK coverage

TacticTechniques
Initial AccessT1190 Exploit Public-Facing Application

Rule body kusto

id: d6abed70-4043-46da-9304-a98f3446fa5f
name: Silverfort - Log4Shell Incident
description: |
  'Vulnerability allows attackers to execute arbitrary code on affected systems by exploiting a flaw in the way Log4j handles log messages containing specially crafted strings'
severity: High
requiredDataConnectors:
  - connectorId: SilverfortAma
    dataTypes:
      - CommonSecurityLog
tactics:
  - InitialAccess
relevantTechniques:
  - T1190 #Exploit Public-Facing Application
query: |-
  CommonSecurityLog 
  | where DeviceVendor has 'Silverfort'
  | where DeviceProduct has 'Admin Console'
  | where DeviceEventClassID == "NewIncident"
  | where Message has "Log4Shell"
  | extend UserName = parse_json(replace('^""|""$', '', Message))['userName']
entityMappings:
  - entityType: Account
    fieldMappings:
      - identifier: Name
        columnName: UserName
queryPeriod: 15m
queryFrequency: 15m
triggerOperator: gt
triggerThreshold: 0
version: 1.0.0
kind: Scheduled

Stages and Predicates

Stage 1: source

CommonSecurityLog

Stage 2: where

| where DeviceVendor has 'Silverfort'

Stage 3: where

| where DeviceProduct has 'Admin Console'

Stage 4: where

| where DeviceEventClassID == "NewIncident"

Stage 5: where

| where Message has "Log4Shell"

Stage 6: extend

| extend UserName = parse_json(replace('^""|""$', '', Message))['userName']

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.

FieldKindValues
DeviceEventClassIDeq
  • NewIncident transforms: cased
DeviceProductmatch
  • Admin Console transforms: term
DeviceVendormatch
  • Silverfort transforms: term
Messagematch
  • Log4Shell transforms: term

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.

FieldSource
UserNameextend