Okta MFA Bruteforce Attack

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 * Copyright 2023 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
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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 okta_mfa_brute_force_attack {

  meta:
    author = "Google Cloud Security"
    description = "Detects a successful login after multiple failed MFA pushes"
    rule_id = "mr_61d8d679-bf4d-4441-bbbb-65f82a37e3c5"
    rule_name = "Okta MFA Bruteforce Attack"
    reference = "https://sec.okta.com/pushfatigueworkflows"
    mitre_attack_tactic = "Credential Access"
    mitre_attack_technique = "Brute Force"
    mitre_attack_url = "https://attack.mitre.org/techniques/T1110/"
    mitre_attack_version = "v13.1"
    type = "Hunt"
    data_source = "Okta"
    severity = "Medium"
    priority = "Medium"

  events:
    $push.metadata.product_name = "Okta"
    $push.metadata.vendor_name = "Okta"
    $push.metadata.event_type = "USER_UNCATEGORIZED"
    $push.metadata.product_event_type = "system.push.send_factor_verify_push"
    $push.network.parent_session_id = $parent_session_id

    $auth.metadata.event_type = "USER_LOGIN"
    $auth.metadata.product_event_type = "user.authentication.auth_via_mfa"
    $auth.metadata.product_name = "Okta"
    $auth.metadata.vendor_name = "Okta"
    $auth.security_result.action = "ALLOW"
    $auth.network.parent_session_id = $parent_session_id

    $push.metadata.event_timestamp.seconds <= $auth.metadata.event_timestamp.seconds

  match:
    $parent_session_id over 15m

  outcome:
    $risk_score = max(35)
    $mitre_attack_tactic = "Credential Access"
    $mitre_attack_technique = "Brute Force"
    $push_target_user_agent = array_distinct($push.network.http.user_agent)
    $push_principal_ip = array_distinct($push.principal.ip)
    $push_principal_ip_country = array_distinct($push.principal.ip_geo_artifact.location.country_or_region)
    $push_principal_ip_state = array_distinct($push.principal.ip_geo_artifact.location.state)
    //$push_principal_ip_city = array_distinct($push.principal.location.city)
    $push_principal_user_email_addresses = array_distinct ($push.principal.user.email_addresses)
    $push_security_result_summary = array_distinct($push.security_result.summary)
    $push_target_user_email_addresses = array_distinct($push.target.user.email_addresses)
    $push_target_user_userid = array_distinct($push.target.user.userid)
    $push_security_result_risk_reason = array_distinct($push.security_result.detection_fields["Risk Reasons"])
    $dc_push_network_session_id = count_distinct($push.network.parent_session_id)
    $auth_target_user_agent = array_distinct($auth.network.http.user_agent)
    $auth_principal_ip = array_distinct($auth.principal.ip)
    $auth_principal_ip_country = array_distinct($auth.principal.ip_geo_artifact.location.country_or_region)
    //$auth_principal_ip_state = array_distinct($auth.principal.ip_geo_artifact.location.state)
    //$auth_principal_ip_city = array_distinct($auth.principal.location.city)
    $auth_principal_user_email_addresses = array_distinct ($auth.principal.user.email_addresses)
    $auth_security_result_summary = array_distinct($auth.security_result.summary)
    $auth_target_user_email_addresses = array_distinct($auth.target.user.email_addresses)
    $auth_target_user_userid = array_distinct($auth.target.user.userid)

  condition:
    #push > 4 and $auth
}