Open redirect: smartadserver.com

name: "Open redirect: smartadserver.com"
description: |
  Message contains use of the smartadserver.com redirect. This has been exploited in the wild.
type: "rule"
severity: "medium"
source: |
  type.inbound
  // smartadserver is used in benign messages, however, they commonly have many links
  // ensure messages contain less than 15 links to ensure higher fidelity matching of malicious messages
  and length(body.links) < 15
  and any(body.links,
          .href_url.domain.root_domain == "smartadserver.com"
          and strings.icontains(.href_url.query_params, 'go=')
          and not regex.icontains(.href_url.query_params,
                                  'go=(?:https?(?:%3a|:))?(?:%2f|\/){2}[^&]*smartadserver\.com(?:\&|\/|$|%2f)'
          )
  )
  // remove uses that originate from smartadserver.com
  and not any(headers.domains, .root_domain == "smartadserver.com")
  // 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: "27e5a585-891d-549d-af34-e2b8dff6d64e"