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

id: 03a8e294-3fc7-4d65-9da2-cff91fb5b6dc
name: TI map Domain entity to DnsEvents
description: |
  Identifies a match in DnsEvents from any Domain IOC from TI
severity: Medium
requiredDataConnectors:
  - connectorId: DNS
    dataTypes:
      - DnsEvents
  - 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: |
  // Define the lookback periods for time-based filters
  let dt_lookBack = 1h; // Look back 1 hour for DNS events
  let ioc_lookBack = 14d; // Look back 14 days for threat intelligence indicators
  // Fetch threat intelligence indicators related to domains
  let Domain_Indicators = ThreatIntelIndicators
    // Filter out indicators without domain names
    | extend IndicatorType = replace(@"\[|\]|\""", "", tostring(split(ObservableKey, ":", 0)))
    | where isnotempty(IndicatorType) and IndicatorType == "domain-name"
    | extend DomainName = tolower(ObservableValue)
    | extend TI_DomainEntity = DomainName
    | extend TrafficLightProtocolLevel = tostring(parse_json(AdditionalFields).TLPLevel)
    | extend Url = iff(ObservableKey == "url:value", ObservableValue, "")
    | 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;
  // Create a list of TLDs in our threat feed for later validation
  let maxListSize = 100000; // Define the maximum allowed size for each list
  let list_tlds = Domain_Indicators
    | extend parts = split(DomainName, '.')
    | extend tld = parts[(array_length(parts)-1)]
    | extend IndicatorId = tostring(split(Id, "--")[2])
    | summarize count() by tostring(tld)
    | project tld
    | summarize make_list(tld, maxListSize);
  // Perform a join between domain indicators and DNS events to identify potential malicious activity
  Domain_Indicators
   | project-reorder *, IsActive, Tags, TrafficLightProtocolLevel, DomainName, Type, TI_DomainEntity
    // Use innerunique to keep performance fast and result set low, as we only need one match to indicate potential malicious activity that needs investigation
    | join kind=innerunique (
      DnsEvents
      | where TimeGenerated > ago(dt_lookBack)
      // Extract domain patterns from syslog message
      | where isnotempty(Name)
      | extend parts = split(Name, '.')
      | 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 DNS_TimeGenerated = TimeGenerated
    ) on $left.TI_DomainEntity==$right.Name
    // Filter out DNS events that occurred after the expiration of the corresponding indicator
    | where DNS_TimeGenerated < ValidUntil
    // Group the results by IndicatorId and Name, and keep the DNS event with the latest timestamp
    | summarize DNS_TimeGenerated = arg_max(DNS_TimeGenerated, *) by Id, Name
    // Select the desired output fields
    | extend ActivityGroupNames = extract(@"ActivityGroup:(\S+)", 1, tostring(parse_json(Data).labels))
    | project DNS_TimeGenerated, Description, ActivityGroupNames, Id, ValidUntil, Confidence, Url, Computer, ClientIP//, Name, QueryType, Type, TI_DomainEntity
    // Extract hostname and DNS domain from the Computer field
    | extend HostName = tostring(split(Computer, '.', 0)[0]), DnsDomain = tostring(strcat_array(array_slice(split(Computer, '.'), 1, -1), '.'))
    // Rename the timestamp field
    | extend timestamp = DNS_TimeGenerated
entityMappings:
  - entityType: Host
    fieldMappings:
      - identifier: FullName
        columnName: Computer
      - identifier: HostName
        columnName: HostName
      - identifier: DnsDomain
        columnName: DnsDomain 
  - entityType: IP
    fieldMappings:
      - identifier: Address
        columnName: ClientIP
  - entityType: URL
    fieldMappings:
      - identifier: Url
        columnName: Url
version: 1.4.4
kind: Scheduled