Enumeration observed in the Microsoft Graph API using GraphRunner GraphRecon command

/*
 * 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 ms_graph_graphrunner_graphrecon_enumeration {

  meta:
    author = "Google Cloud Security"
    description = "Identify the use of the GraphRunner recon command Invoke-GraphRecon with the permission enum flag set, providing allowed actions and conditional access data for the current user."
    rule_id = "mr_2bb3fd42-5569-4bab-9788-855425971b7f"
    rule_name = "Enumeration observed in the Microsoft Graph API using GraphRunner GraphRecon command"
    reference = "https://github.com/dafthack/GraphRunner/blob/main/GraphRunner.ps1"
    type = "Alert"
    data_source = "MS Graph Activity Logs"
    platform = "Azure"
    severity = "Medium"
    priority = "Medium"

  events:
    $api_est.metadata.event_type = "NETWORK_HTTP"
    $api_est.metadata.product_event_type = "Microsoft Graph Activity"
    $api_est.target.url = "https://graph.microsoft.com/beta/roleManagement/directory/estimateAccess" nocase
    //Can be tuned for specific User Agent strings being used - by default GraphRunner does not forge the UA for this action
    //$api_est.network.http.user_agent = /PowerShell/ nocase
    $api_est.network.http.method = "POST"
    $api_est.network.http.response_code = 200
    $api_est.principal.ip = $ip
    $api_est.network.session_id = $session

    $api_me.metadata.event_type = "NETWORK_HTTP"
    $api_me.metadata.product_event_type = "Microsoft Graph Activity"
    $api_me.target.url = "https://graph.microsoft.com/v1.0/me" nocase
    //Can be tuned for specific User Agent strings being used - by default GraphRunner does not forge the UA for this action
    //$api_me.network.http.user_agent = /PowerShell/ nocase
    $api_me.network.http.method = "GET"
    $api_me.network.http.response_code = 200
    $api_me.principal.ip = $ip
    $api_me.network.session_id = $session

    $api_auth.metadata.event_type = "NETWORK_HTTP"
    $api_auth.metadata.product_event_type = "Microsoft Graph Activity"
    $api_auth.target.url = "https://graph.microsoft.com/beta/policies/authorizationPolicy" nocase
    //Can be tuned for specific User Agent strings being used - by default GraphRunner does not forge the UA for this action
    //$api_auth.network.http.user_agent = /PowerShell/ nocase
    $api_auth.network.http.method = "GET"
    $api_auth.network.http.response_code = 200
    $api_auth.principal.ip = $ip
    $api_auth.network.session_id = $session

  match:
    $ip, $session over 5m

  outcome:
    $risk_score = 65
    $event_count = count_distinct($api_est.metadata.id) + count_distinct($api_auth.metadata.id) + count_distinct($api_me.metadata.id)
    $requesting_user_guid = array_distinct($api_est.principal.user.userid)
    $requesting_ip = array_distinct($api_est.principal.ip)
    $user_agent = array_distinct($api_est.network.http.user_agent)
    $location = array_distinct($api_est.principal.location.name)
    $target_application_id_guid = array_distinct($api_est.target.resource.product_object_id)
    $session_id = array_distinct($api_est.network.session_id)

  condition:
    $api_est and $api_auth and $api_me
}