Detection rules › Kusto

TI map File Hash to CommonSecurityLog Event

Severity
medium
Time window
14d
Group by
FileHash, FileHashValue, IndicatorId
Source
github.com/Azure/Azure-Sentinel

'Identifies a match in CommonSecurityLog Event data from any FileHash IOC from TI'

MITRE ATT&CK coverage

TacticTechniques
Command & ControlT1071 Application Layer Protocol

Rule body kusto

id: 5d33fc63-b83b-4913-b95e-94d13f0d379f
name: TI map File Hash to CommonSecurityLog Event
description: |
  'Identifies a match in CommonSecurityLog Event data from any FileHash IOC from TI'
severity: Medium
requiredDataConnectors:
  - connectorId: PaloAltoNetworks
    dataTypes:
      - CommonSecurityLog
  - connectorId: ThreatIntelligence
    dataTypes:
      - ThreatIntelligenceIndicator
  - connectorId: ThreatIntelligenceTaxii
    dataTypes:
      - ThreatIntelligenceIndicator
  - connectorId: MicrosoftDefenderThreatIntelligence
    dataTypes:
      - ThreatIntelligenceIndicator
queryFrequency: 1h
queryPeriod: 14d
triggerOperator: gt
triggerThreshold: 0
tactics:
  - CommandAndControl
relevantTechniques:
  - T1071
query: |
  let dt_lookBack = 1h;
  let ioc_lookBack = 14d;
  let fileHashIndicators = ThreatIntelligenceIndicator
  | where isnotempty(FileHashValue)
  | where TimeGenerated >= ago(ioc_lookBack)
  | summarize LatestIndicatorTime = arg_max(TimeGenerated, *) by IndicatorId
  | where Active == true and ExpirationDateTime > now();
  // Handle matches against both lower case and uppercase versions of the hash:
  (fileHashIndicators | extend  FileHashValue = tolower(FileHashValue)
  | union (fileHashIndicators | extend FileHashValue = toupper(FileHashValue)))
  // using innerunique to keep perf fast and result set low, we only need one match to indicate potential malicious activity that needs to be investigated
  |  join kind=innerunique (
    CommonSecurityLog | where TimeGenerated >= ago(dt_lookBack)
    | where isnotempty(FileHash)
    | extend CommonSecurityLog_TimeGenerated = TimeGenerated
    )
  on $left.FileHashValue == $right.FileHash
  | where CommonSecurityLog_TimeGenerated < ExpirationDateTime
  | summarize CommonSecurityLog_TimeGenerated = arg_max(CommonSecurityLog_TimeGenerated, *) by IndicatorId, FileHashValue
  | project CommonSecurityLog_TimeGenerated, Description, ActivityGroupNames, IndicatorId, ThreatType, Url, ExpirationDateTime, ConfidenceScore,
  SourceIP, SourcePort, DestinationIP, DestinationPort, SourceUserID, SourceUserName, DeviceName, DeviceAction,
  RequestURL, DestinationUserName, DestinationUserID, ApplicationProtocol, Activity, FileHashValue, FileHashType
  | extend HostName = tostring(split(DeviceName, '.', 0)[0]), DnsDomain = tostring(strcat_array(array_slice(split(DeviceName, '.'), 1, -1), '.'))
  | extend Name = tostring(split(SourceUserName, '@', 0)[0]), UPNSuffix = tostring(split(SourceUserName, '@', 1)[0])
  | extend timestamp = CommonSecurityLog_TimeGenerated
entityMappings:
  - entityType: Account
    fieldMappings:
      - identifier: FullName
        columnName: SourceUserName
      - identifier: Name
        columnName: Name
      - identifier: UPNSuffix
        columnName: UPNSuffix 
  - entityType: Host
    fieldMappings:
      - identifier: FullName
        columnName: DeviceName
      - identifier: HostName
        columnName: HostName
      - identifier: DnsDomain
        columnName: DnsDomain
  - entityType: IP
    fieldMappings:
      - identifier: Address
        columnName: SourceIP
  - entityType: URL
    fieldMappings:
      - identifier: Url
        columnName: Url
  - entityType: FileHash
    fieldMappings:
      - identifier: Value
        columnName: FileHashValue
      - identifier: Algorithm
        columnName: FileHashType
version: 1.3.6
kind: Scheduled

Stages and Predicates

Parameters

let dt_lookBack = 1h;
let ioc_lookBack = 14d;

The stages below define let fileHashIndicators (the rule's main pipeline source).

Stage 1: source

ThreatIntelligenceIndicator

Stage 2: where

| where isnotempty(FileHashValue)

Stage 3: where

| where TimeGenerated >= ago(ioc_lookBack)

Stage 4: summarize

| summarize LatestIndicatorTime = arg_max(TimeGenerated, *) by IndicatorId

Stage 5: where

| where Active == true and ExpirationDateTime > now()

The stages below run on fileHashIndicators (the outer pipeline).

Stage 6: extend

fileHashIndicators
| extend  FileHashValue = tolower(FileHashValue)

Stage 7: union

| union

Stage 8: source

ThreatIntelligenceIndicator

Stage 9: where

| where isnotempty(FileHashValue)

Stage 10: where

| where TimeGenerated >= ago(ioc_lookBack)

Stage 11: summarize

| summarize LatestIndicatorTime = arg_max(TimeGenerated, *) by IndicatorId

Stage 12: where

| where Active == true and ExpirationDateTime > now()

Stage 13: extend

| extend FileHashValue = toupper(FileHashValue)

Stage 14: join

| join kind=innerunique (
  CommonSecurityLog | where TimeGenerated >= ago(dt_lookBack)
  | where isnotempty(FileHash)
  | extend CommonSecurityLog_TimeGenerated = TimeGenerated
  )
on $left.FileHashValue == $right.FileHash

Stage 15: where

| where CommonSecurityLog_TimeGenerated < ExpirationDateTime

Stage 16: summarize

| summarize CommonSecurityLog_TimeGenerated = arg_max(CommonSecurityLog_TimeGenerated, *) by IndicatorId, FileHashValue

Stage 17: project

| project CommonSecurityLog_TimeGenerated, Description, ActivityGroupNames, IndicatorId, ThreatType, Url, ExpirationDateTime, ConfidenceScore,
SourceIP, SourcePort, DestinationIP, DestinationPort, SourceUserID, SourceUserName, DeviceName, DeviceAction,
RequestURL, DestinationUserName, DestinationUserID, ApplicationProtocol, Activity, FileHashValue, FileHashType

Stage 18: extend (3 consecutive steps)

| extend HostName = tostring(split(DeviceName, '.', 0)[0]), DnsDomain = tostring(strcat_array(array_slice(split(DeviceName, '.'), 1, -1), '.'))
| extend Name = tostring(split(SourceUserName, '@', 0)[0]), UPNSuffix = tostring(split(SourceUserName, '@', 1)[0])
| extend timestamp = CommonSecurityLog_TimeGenerated

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
Activeeq
  • true transforms: cased
CommonSecurityLog_TimeGeneratedlt
  • ExpirationDateTime transforms: cased
FileHashis_not_null
  • (no value, null check)
FileHashValueis_not_null
  • (no value, null check)

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
Activityproject
ActivityGroupNamesproject
ApplicationProtocolproject
CommonSecurityLog_TimeGeneratedproject
ConfidenceScoreproject
Descriptionproject
DestinationIPproject
DestinationPortproject
DestinationUserIDproject
DestinationUserNameproject
DeviceActionproject
DeviceNameproject
ExpirationDateTimeproject
FileHashTypeproject
FileHashValueproject
IndicatorIdproject
RequestURLproject
SourceIPproject
SourcePortproject
SourceUserIDproject
SourceUserNameproject
ThreatTypeproject
Urlproject
DnsDomainextend
HostNameextend
Nameextend
UPNSuffixextend
timestampextend