Open redirect: business.google.com website_shared URL Param

name: "Open redirect: business.google.com website_shared URL Param"
description: |
  Detects messages containing an open redirect in business.google.com's 
  website_shared/launch_bw.html endpoint with the 'f' parameter. This has been 
  exploited in phishing campaigns to redirect users to malicious sites.
type: "rule"
severity: "medium"
source: |
  type.inbound
  and any(body.links,
          .href_url.domain.domain == "business.google.com"
          and strings.icontains(.href_url.path, '/website_shared/launch_bw.html')
          and strings.icontains(.href_url.query_params, 'f=')
          // Make sure the redirect is not going back to google.com
          and not regex.icontains(.href_url.query_params,
                                  'f=(?:https?(?:%3a|:))?(?:%2f|\/){2}[^&]*google\.com(?:\&|\/|$|%2f)'
          )
  )
  // Exclude legitimate Google domains as senders
  and not regex.icontains(sender.email.domain.root_domain, '^google')
  
  // negate highly trusted sender domains unless they fail DMARC authentication
  and (
    (
      sender.email.domain.root_domain in $high_trust_sender_root_domains
      and not headers.auth_summary.dmarc.pass
    )
    or sender.email.domain.root_domain not in $high_trust_sender_root_domains
  )
attack_types:
  - "Credential Phishing"
  - "Malware/Ransomware"
tactics_and_techniques:
  - "Open redirect"
detection_methods:
  - "Sender analysis"
  - "URL analysis"
id: "f146be73-7200-570e-a033-a28814c5a098"