AWS Unusual Number Of Failed Authentication Attempts From The Same IP

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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 aws_unusual_number_of_failed_authentications_from_the_same_ip {

  meta:
    author = "Google Cloud Security"
    description = "Detects unusual number of failed authentications from the same IP for valid users."
    rule_id = "mr_cf1787a4-0145-4093-ad35-2de17f1980ce"
    rule_name = "AWS Unusual Number Of Failed Authentication Attempts From The Same IP"
    mitre_attack_tactic = "Credential Access"
    mitre_attack_technique = "Brute Force: Credential Stuffing"
    mitre_attack_url = "https://attack.mitre.org/techniques/T1110/004/"
    mitre_attack_version = "v13.1"
    type = "Alert"
    data_source = "AWS CloudTrail"
    platform = "AWS"
    severity = "Medium"
    priority = "Medium"

  events:
    $fail.metadata.vendor_name = "AMAZON"
    $fail.metadata.product_name = "AWS CloudTrail"
    $fail.metadata.event_type = "USER_LOGIN"
    $fail.metadata.product_event_type = "ConsoleLogin"
    $fail.security_result.action = "BLOCK"
    $fail.security_result.description = "Reason: Failed authentication"
    $fail.principal.ip = $ip

  match:
    $ip over 5m

  outcome:
    $risk_score = max(
        // Unauthorized geographies
        if($fail.principal.ip_geo_artifact.location.country_or_region = "Cuba", 40) +
        if($fail.principal.ip_geo_artifact.location.country_or_region = "Iran", 40) +
        if($fail.principal.ip_geo_artifact.location.country_or_region = "North Korea" , 40) +
        if($fail.principal.ip_geo_artifact.location.country_or_region = "Russia", 40) +
        if($fail.principal.ip_geo_artifact.location.country_or_region = "Syria", 40)
    )
    $mitre_attack_tactic = "Credential Access"
    $mitre_attack_technique = "Brute Force: Credential Stuffing"
    $mitre_attack_technique_id = "T1110.004"
    $event_count = count_distinct($fail.metadata.id)
    $network_http_user_agent = array_distinct($fail.network.http.user_agent)
    $principal_ip = array_distinct($fail.principal.ip)
    $principal_ip_country = array_distinct($fail.principal.ip_geo_artifact.location.country_or_region)
    $principal_ip_state = array_distinct($fail.principal.ip_geo_artifact.location.state)
    $principal_user_display_name = array_distinct($fail.principal.user.user_display_name)
    $dc_target_user_display_name = count_distinct($fail.target.user.user_display_name)
    $is_mfa_used = array_distinct($fail.extensions.auth.auth_details)
    $target_resource_name = array_distinct($fail.target.resource.name)
    $target_resource_product_object_id = array_distinct($fail.target.resource.product_object_id)

  condition:
    $fail and $dc_target_user_display_name > 5
}