Solutions/Threat Intelligence (NEW)/Analytic Rules/DomainEntity_Syslog.yaml

id: cd19434e-10f2-4e2f-b3c1-ce6f08ac5357
name: TI map Domain entity to Syslog
description: |
  Identifies a match in Syslog table from any Domain IOC from TI
severity: Medium
requiredDataConnectors:
  - connectorId: Syslog
    dataTypes:
      - Syslog
  - 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;  // Define the time range to look back for syslog data (1 hour)
  let ioc_lookBack = 14d;  // Define the time range to look back for threat intelligence indicators (14 days)
  // Create a list of top-level domains (TLDs) from the threat feed for later validation
  let list_tlds = ThreatIntelligenceIndicator
    | where isnotempty(DomainName)
    | where TimeGenerated > ago(ioc_lookBack)
    | summarize LatestIndicatorTime = arg_max(TimeGenerated, *) by IndicatorId
    | where Active == true and ExpirationDateTime > now()
    | extend parts = split(DomainName, '.')
    | extend tld = parts[(array_length(parts)-1)]
    | summarize count() by tostring(tld)
    | summarize make_list(tld);
  // Fetch the latest active domain indicators from the threat intelligence data within the specified time range
  let Domain_Indicators = ThreatIntelIndicators
  | extend IndicatorType = replace(@"\[|\]|\""", "", tostring(split(ObservableKey, ":", 0)))
  | where isnotempty(IndicatorType) and IndicatorType == "domain-name"
  | extend DomainName = tolower(ObservableValue)
  | extend TrafficLightProtocolLevel = tostring(parse_json(AdditionalFields).TLPLevel)
    | where isnotempty(DomainName)
    | where TimeGenerated >= ago(ioc_lookBack)
    | summarize LatestIndicatorTime = arg_max(TimeGenerated, *) by Id
    | where IsActive == true and ValidUntil > now()
    | extend TI_DomainEntity = DomainName
    | extend IndicatorId = tostring(split(Id, "--")[2])
    | extend Url = iff(ObservableKey == "url:value", ObservableValue, "");
  // Join the threat intelligence indicators with syslog data on matching domain entities
  Domain_Indicators
  | project-reorder *, IsActive, Tags, TrafficLightProtocolLevel, DomainName, Type, TI_DomainEntity
    | join kind=innerunique (
      Syslog
      | where TimeGenerated > ago(dt_lookBack)
      // Extract domain patterns from syslog messages
      | extend domain = extract("(([a-z0-9]+(-[a-z0-9]+)*\\.)+[a-z]{2,})",1, tolower(SyslogMessage))
      | where isnotempty(domain)
      | extend parts = split(domain, '.')
      // Split out the top-level domain (TLD)
      | extend tld = parts[(array_length(parts)-1)]
      // Validate parsed domain by checking if the TLD is in the list of TLDs in our threat feed
      | where tld in~ (list_tlds)
      | extend Syslog_TimeGenerated = TimeGenerated
    ) on $left.TI_DomainEntity==$right.domain
    | where Syslog_TimeGenerated < ValidUntil
    // Retrieve the latest syslog timestamp for each indicator and domain combination
    | summarize Syslog_TimeGenerated = arg_max(Syslog_TimeGenerated, *) by IndicatorId, domain
    // Select the desired columns for the final result set
    | extend ActivityGroupNames = extract(@"ActivityGroup:(\S+)", 1, tostring(parse_json(Data).labels))
    | extend Description = tostring(parse_json(Data).description)
    | project Syslog_TimeGenerated, Description, ActivityGroupNames, Id, ValidUntil, Confidence, SyslogMessage, Computer, ProcessName, domain, HostIP, Type, TI_DomainEntity, Url
    // Extract the hostname from the Computer field
    | extend HostName = tostring(split(Computer, '.', 0)[0])
    // Extract the DNS domain from the Computer field
    | extend DnsDomain = tostring(strcat_array(array_slice(split(Computer, '.'), 1, -1), '.'))
    // Assign the Syslog_TimeGenerated value to the timestamp field
    | extend timestamp = Syslog_TimeGenerated
entityMappings:
  - entityType: Host
    fieldMappings:
      - identifier: FullName
        columnName: Computer
      - identifier: HostName
        columnName: HostName
      - identifier: DnsDomain
        columnName: DnsDomain
  - entityType: IP
    fieldMappings:
      - identifier: Address
        columnName: HostIP
  - entityType: URL
    fieldMappings:
      - identifier: Url
        columnName: Url
version: 1.4.4
kind: Scheduled