O365 Entra ID App Client Secret Added, Updated or Deleted

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 * Copyright 2025 Google LLC
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 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     https://www.apache.org/licenses/LICENSE-2.0
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 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
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rule o365_entra_id_client_secret_add_update_delete_in_app {

  meta:
    author = "Google Cloud Security"
    description = "Secrets added to applications have legitimate purposes, but can also be a method of persistence. This alert will trigger on creation, modification or delete of a client secret"
    rule_id = "mr_24ac7907-9d86-4089-901c-61f8ff1e7730"
    rule_name = "O365 Entra ID App Client Secret Added, Updated or Deleted"
    tactic = "TA0003"
    technique = "T1098.001"
    type = "alert"
    platform = "azure"
    data_source = "o365"
    severity = "Medium"
    priority = "Medium"

  events:
    $app.metadata.event_type = "USER_RESOURCE_UPDATE_CONTENT"
    $app.metadata.product_name = "Office 365"
    $app.metadata.product_event_type = /Update application.*Certificates and secrets management/
    $app.metadata.vendor_name = "Microsoft"
    $app.security_result.action = "ALLOW"
    $app.principal.user.userid = $userid

  match:
    $userid over 5m

  outcome:
    $risk_score = 65
    $event_count = count_distinct($app.metadata.id)
    $security_summary = array_distinct($app.security_result.summary)
    $user_agent = array_distinct($app.network.http.user_agent)
    $target_entra_id_application = array_distinct(re.capture($app.network.http.user_agent,`\"AppId\":\"(.*)`))
    //added to populate alert graph with additional context
    $principal_user_userid = array_distinct($app.principal.user.userid)

  condition:
    $app
}