Office 365 Teams member removed

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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.
 */

 rule o365_teams_member_removed {

meta:
    author = "Google Cloud Security"
    description = "Detects when a user is removed from a group in Microsoft Teams."
    rule_id = "mr_9cbf9cc6-35ae-44bd-8c2c-3ed4f8ea528f"
    rule_name = "Office 365 Teams member removed"
    type = "alert"
    platform = "azure"
    data_source = "o365"
    severity = "Low"
    priority = "Low"

events:
    $app.metadata.product_name = "Office 365"
    $app.metadata.vendor_name = "Microsoft"
    $app.metadata.log_type = "OFFICE_365"
    $app.metadata.product_event_type = "MemberRemoved"
    $app.about.user.user_display_name = $userid
    $app.target.application = "MicrosoftTeams"
    $app.metadata.event_type = "USER_CHANGE_PERMISSIONS"
    $app.security_result.action = "UNKNOWN_ACTION"

match:
    $userid over 5m

outcome:
    $risk_score = 35
    $event_count = count_distinct($app.metadata.id)
    $target_application = array_distinct($app.target.application)
    $principal_user_userid = array_distinct($app.principal.user.userid)
    $group_name = array_distinct($app.target.group.group_display_name)
    $group_id = array_distinct($app.target.group.product_object_id)
    $removed_user_email = array_distinct($app.about.user.email_addresses)
    $removed_user_name = array_distinct($app.about.user.user_display_name)

condition:
$app
}