AWS MultiFactor Authentication Disabled

// Copyright 2023 Google LLC. Licensed under Apache-2.0.

rule aws_multi_factor_authentication_disabled {

  meta:
    author = "Google Cloud Security"
    description = "Detects attempts to disable multi-factor authentication for an AWS IAM user."
    rule_id = "mr_0d6bd993-c80b-4367-a921-5a542ab826b3"
    rule_name = "AWS MultiFactor Authentication Disabled"
    mitre_attack_tactic = "Credential Access, Defense Evasion, Persistence"
    mitre_attack_technique = "Modify Authentication Process: Multi-Factor Authentication"
    mitre_attack_url = "https://attack.mitre.org/techniques/T1556/006/"
    mitre_attack_version = "v13.1"
    type = "Alert"
    data_source = "AWS CloudTrail"
    platform = "AWS"
    severity = "Medium"
    priority = "Medium"

  events:
    $cloudtrail.metadata.vendor_name = "AMAZON"
    $cloudtrail.metadata.product_name = "AWS CloudTrail"
    (
      $cloudtrail.metadata.product_event_type = "DeleteVirtualMFADevice" or
      $cloudtrail.metadata.product_event_type = "DeactivateMFADevice"
    )
    $cloudtrail.security_result.action = "ALLOW"
    $cloudtrail.principal.user.user_display_name = $user_id

  match:
    $user_id over 1h

  outcome:
    $risk_score = max(
        //Baseline
        35 +
        // High Risk for AWS Root User
        if($cloudtrail.src.user.user_display_name = "AWS Root User", 50)
    )
    $mitre_attack_tactic = "Credential Access, Defense Evasion, Persistence"
    $mitre_attack_technique = "Modify Authentication Process: Multi-Factor Authentication"
    $mitre_attack_technique_id = "T1556.006"
    $event_count = count_distinct($cloudtrail.metadata.id)
    $network_http_user_agent = array_distinct($cloudtrail.network.http.user_agent)
    $principal_ip = array_distinct($cloudtrail.principal.ip)
    $principal_ip_country = array_distinct($cloudtrail.principal.ip_geo_artifact.location.country_or_region)
    $principal_ip_state = array_distinct($cloudtrail.principal.ip_geo_artifact.location.state)
    $principal_user_display_name = array_distinct($cloudtrail.principal.user.user_display_name)
    $recipient_aws_account_id = array_distinct($cloudtrail.additional.fields["recipientAccountId"])
    $aws_region = array_distinct($cloudtrail.principal.location.name)
    $target_resource_name = array_distinct($cloudtrail.target.resource.name)
    $target_resource_product_object_id = array_distinct($cloudtrail.target.resource.product_object_id)

  condition:
    $cloudtrail
}