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

Tactic	Techniques
Initial Access	`T1190` Exploit Public-Facing Application

Rule body

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

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`DeviceEventClassID`	eq	`NewIncident`	`field:"DeviceEventClassID" kind:eq value:"NewIncident"`
`DeviceProduct`	match	`Admin Console` transforms: `term`	`field:"DeviceProduct" kind:match value:"Admin Console"`
`DeviceVendor`	match	`Silverfort` transforms: `term`	`field:"DeviceVendor" kind:match value:"Silverfort"`
`Message`	match	`Log4Shell` transforms: `term`	`field:"Message" kind:match value:"Log4Shell"`

Output fields

These fields are emitted when the rule matches.

Field	Source
`UserName`	`extend`

Silverfort - Log4Shell Incident

MITRE ATT&CK coverage

Rule body

Stages and Predicates

Stage 1: source

Stage 2: where

Stage 3: where

Stage 4: where

Stage 5: where

Stage 6: extend