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Detection rules › YARA-L

Client Secret Added to Entra ID Application

Severity
medium
Type
alert
Time window
5m
Match by
user
Author
Google Cloud Security
Source
github.com/chronicle/detection-rules

Secrets added to applications have legitimate purposes, but can also be a method of persistence.

MITRE ATT&CK coverage

TacticTechniques
PersistenceT1098.001 Account Manipulation: Additional Cloud Credentials

Rule body yaral

/*
 * Copyright 2025 Google LLC
 *
 * 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
 *
 * 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.
 */

 rule entra_id_secret_added_to_app {

  meta:
    author = "Google Cloud Security"
    description = "Secrets added to applications have legitimate purposes, but can also be a method of persistence."
    rule_id = "mr_22d3881f-f84d-42ee-a1bc-5d5eb419b769"
    rule_name = "Client Secret Added to Entra ID Application"
    tactic = "TA0003"
    technique = "T1098.001"
    type = "alert"
    platform = "azure"
    data_source = "azure ad"
    severity = "Medium"
    priority = "Medium"

  events:
    $app.metadata.event_type = "SERVICE_MODIFICATION"
    $app.metadata.product_event_type = /Update application.*Certificates and secrets management/
    $app.metadata.product_name = "Azure AD Directory Audit"
    $app.metadata.vendor_name = "Microsoft"
    $app.security_result.action = "ALLOW"
    $app.principal.user.userid = $user

  match:
    $user over 5m

  outcome:
    $risk_score = 65
    $event_count = count_distinct($app.metadata.id)
    $user_agent = array_distinct($app.network.http.user_agent)
    $network_session = array_distinct($app.network.session_id)
    $principal_county_region = array_distinct($app.principal.ip_geo_artifact.location.country_or_region)
    $principal_ip = array_distinct($app.principal.ip)
    $principal_email = array_distinct($app.principal.user.email_addresses)
    $target_application = array_distinct($app.target.resource.name)
    $target_application_id = array_distinct($app.target.resource.product_object_id)

  condition:
    $app
}

Detection logic

Fires when at least one $app event in the 5m window.

Events

$app SERVICE_MODIFICATION

  • metadata.product_event_type matches "Update application.*Certificates and secrets management"
  • security_result.action = "ALLOW"

Correlation

Match key
$user (principal.user.userid)
Within
5m

Outcome

Fields the detection emits on a match. $risk_score drives alerting; Chronicle surfaces the rest on the detection.

FieldExpression
risk_score65
event_countcount_distinct($app.metadata.id)
user_agentarray_distinct($app.network.http.user_agent)
network_sessionarray_distinct($app.network.session_id)
principal_county_regionarray_distinct($app.principal.ip_geo_artifact.location.country_or_region)
principal_iparray_distinct($app.principal.ip)
principal_emailarray_distinct($app.principal.user.email_addresses)
target_applicationarray_distinct($app.target.resource.name)
target_application_idarray_distinct($app.target.resource.product_object_id)