Open redirect: emp.eduyield.com

 1name: "Open redirect: emp.eduyield.com"
 2description: |
 3    Message contains use of the eduyield redirect which chains google amp. This has been exploited in the wild.
 4type: "rule"
 5severity: "medium"
 6source: |
 7  type.inbound
 8  and any(body.links,
 9          .href_url.domain.domain == "emp.eduyield.com"
10          // the redirect field
11          and strings.icontains(.href_url.query_params, "&dest=")
12          and regex.icontains(.href_url.query_params,
13                              '&dest=(?:https?)?(?:(?:%3a|\:)?(?:\/|%2f){2})?google\.com[^\&]*\/+amp\/+(s\/+)?'
14          )
15  )
16  and (
17    not profile.by_sender().solicited
18    or (
19      profile.by_sender().any_messages_malicious_or_spam
20      and not profile.by_sender().any_messages_benign
21    )
22  )
23  
24  // negate highly trusted sender domains unless they fail DMARC authentication
25  and not (
26    sender.email.domain.root_domain in $high_trust_sender_root_domains
27    and coalesce(headers.auth_summary.dmarc.pass, false)
28  )  
29attack_types:
30  - "Credential Phishing"
31  - "Malware/Ransomware"
32tactics_and_techniques:
33  - "Open redirect"
34detection_methods:
35  - "Sender analysis"
36  - "URL analysis"
37id: "860e1381-a99a-5b6e-bfed-ef0931e06fc7"