Open Redirect: smartadserver.com

 1name: "Open Redirect: smartadserver.com"
 2description: |
 3    Message contains use of the smartadserver.com redirect. This has been exploited in the wild.
 4type: "rule"
 5severity: "medium"
 6source: |
 7  type.inbound
 8  // smartadserver is used in benign messages, however, they commonly have many links
 9  // ensure messages contain less than 15 links to ensure higher fidelity matching of malicious messages
10  and length(body.links) < 15
11  and any(body.links,
12      .href_url.domain.root_domain == "smartadserver.com"
13      and strings.icontains(.href_url.query_params, 'go=')
14      and not regex.icontains(.href_url.query_params,
15                                'go=(?:https?(?:%3a|:))?(?:%2f|\/){2}[^&]*smartadserver\.com(?:\&|\/|$|%2f)'
16      )
17  )
18  // remove uses that originate from smartadserver.com
19  and not any(headers.domains, .root_domain == "smartadserver.com")
20  // negate highly trusted sender domains unless they fail DMARC authentication
21  and (
22    (
23      sender.email.domain.root_domain in $high_trust_sender_root_domains
24      and not headers.auth_summary.dmarc.pass
25    )
26    or sender.email.domain.root_domain not in $high_trust_sender_root_domains
27  )  
28attack_types:
29  - "Credential Phishing"
30  - "Malware/Ransomware"
31tactics_and_techniques:
32  - "Open redirect"
33detection_methods:
34  - "Sender analysis"
35  - "URL analysis"
36id: "27e5a585-891d-549d-af34-e2b8dff6d64e"