Red Sift - New email with URL from previously unseen sender

id: 6e0b70d4-0ab8-480e-9707-8ad45fc21a65
name: Red Sift - New email with URL from previously unseen sender
description: |
  'Detects email forensics events that contain one or more URLs where the sender in the from field has not been seen in the previous 14 days, which may indicate phishing activity or a newly observed sender.'
severity: Medium
status: Available
requiredDataConnectors:
  - connectorId: RedSiftPush
    dataTypes:
      - RedSiftEmailForensics_CL
queryFrequency: 1h
queryPeriod: 14d
triggerOperator: gt
triggerThreshold: 0
tactics:
  - InitialAccess
relevantTechniques:
  - T1566
query: |
  let lookback = 14d;
  let recentWindow = 1h;
  let historicalSenders = RedSiftEmailForensics_CL
  | extend
      EmailFrom = tostring(column_ifexists("EmailFrom", ""))
  | where TimeGenerated between (ago(lookback) .. ago(recentWindow))
  | where isnotempty(EmailFrom)
  | summarize by EmailFrom;
  RedSiftEmailForensics_CL
  | extend
      EmailFrom = tostring(column_ifexists("EmailFrom", "")),
      EmailSubject = tostring(column_ifexists("EmailSubject", "")),
      EmailReturnPath = tostring(column_ifexists("EmailReturnPath", "")),
      EmailMessageUid = tostring(column_ifexists("EmailMessageUid", "")),
      SrcIp = tostring(column_ifexists("SrcIp", "")),
      DstHostname = tostring(column_ifexists("DstHostname", "")),
      Severity = tostring(column_ifexists("Severity", "")),
      Message = tostring(column_ifexists("Message", "")),
      CorrelationUid = tostring(column_ifexists("CorrelationUid", "")),
      EmailUrls = todynamic(column_ifexists("EmailUrls", "[]"))
  | where TimeGenerated >= ago(recentWindow)
  | where isnotempty(EmailFrom)
  | extend UrlCount = array_length(EmailUrls)
  | where UrlCount > 0
  | mv-apply Url = EmailUrls on (
      summarize UrlSet = make_set(tostring(Url.url_string), 50)
    )
  | extend UrlList = strcat_array(UrlSet, ", ")
  | join kind=leftanti (historicalSenders) on EmailFrom
  | project
      TimeGenerated,
      EmailFrom,
      EmailSubject,
      EmailReturnPath,
      EmailMessageUid,
      SrcIp,
      DstHostname,
      UrlCount,
      UrlList,
      Severity,
      Message,
      CorrelationUid
entityMappings:
  - entityType: Account
    fieldMappings:
      - identifier: FullName
        columnName: EmailFrom
  - entityType: IP
    fieldMappings:
      - identifier: Address
        columnName: SrcIp
  - entityType: DNS
    fieldMappings:
      - identifier: DomainName
        columnName: DstHostname
customDetails:
  EmailSubject: EmailSubject
  ReturnPath: EmailReturnPath
  UrlCount: UrlCount
  UrlList: UrlList
  CorrelationUid: CorrelationUid
alertDetailsOverride:
  alertDisplayNameFormat: "RedSift - New URL-bearing sender {{EmailFrom}}"
  alertDescriptionFormat: "Email from previously unseen sender {{EmailFrom}} contains {{UrlCount}} URL(s)."
incidentConfiguration:
  createIncident: true
  groupingConfiguration:
    enabled: true
    reopenClosedIncident: false
    lookbackDuration: P1D
    matchingMethod: Selected
    groupByEntities:
      - Account
    groupByCustomDetails:
      - EmailSubject
eventGroupingSettings:
  aggregationKind: AlertPerResult
suppressionEnabled: false
suppressionDuration: PT1H
version: 1.0.0
kind: Scheduled