AWS Password Policy Change

Severity: medium
Type: Alert
Author: Google Cloud Security
Source: github.com/chronicle/detection-rules

Detects when an existing password policy is updated or deleted in an AWS account.

MITRE ATT&CK coverage

Tactic	Techniques
Discovery	`T1201` Password Policy Discovery

Telemetry coverage

Platform	Record / event type
AWS	CloudTrail event `DeleteAccountPasswordPolicy`: Deletes the password policy for the AWS account, reverting to default password requirements.
AWS	CloudTrail event `UpdateAccountPasswordPolicy`: Updates the password policy for the AWS account, setting requirements such as minimum length, complexity, and expiration.

Rule body

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

rule aws_password_policy_change {

  meta:
    author = "Google Cloud Security"
    description = "Detects when an existing password policy is updated or deleted in an AWS account."
    rule_id = "mr_2e66b918-acfc-46ea-b625-58732558005d"
    rule_name = "AWS Password Policy Change"
    mitre_attack_tactic = "Discovery"
    mitre_attack_technique = "Password Policy Discovery"
    mitre_attack_url = "https://attack.mitre.org/techniques/T1201/"
    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 = "UpdateAccountPasswordPolicy" or
     $cloudtrail.metadata.product_event_type = "DeleteAccountPasswordPolicy"
    )
    $cloudtrail.security_result.action = "ALLOW"

  outcome:
    $risk_score = max(50)
    $mitre_attack_tactic = "Discovery"
    $mitre_attack_technique = "Password Policy Discovery"
    $mitre_attack_technique_id = "T1201"
    $event_count = count_distinct($cloudtrail.metadata.id)
    $network_http_user_agent = $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 = $cloudtrail.principal.user.user_display_name
    $recipient_aws_account_id = $cloudtrail.additional.fields["recipientAccountId"]
    $aws_region = $cloudtrail.principal.location.name

  condition:
    $cloudtrail
}

YARA-L rule structure

Condition

Fires when at least one $cloudtrail event.

Events

`$cloudtrail`

metadata.product_event_type is one of:
- UpdateAccountPasswordPolicy
- DeleteAccountPasswordPolicy
security_result.action = "ALLOW"

Outcome

Outcome variables add context to a detection. When the rule generates an alert, $risk_score is displayed with it.

Field	Expression
`risk_score`	`max(50)`
`event_count`	`count_distinct($cloudtrail.metadata.id)`
`network_http_user_agent`	`$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($cloudtrail.principal.ip_geo_artifact.location.state)`
`principal_user_display_name`	`$cloudtrail.principal.user.user_display_name`
`recipient_aws_account_id`	`$cloudtrail.additional.fields["recipientAccountId"]`
`aws_region`	`$cloudtrail.principal.location.name`