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, '&dest=(?:https?)?(?:(?:%3a|\:)?(?:\/|%2f){2})?google\.com[^\&]+\/+amp\/+s\/+')
13  )
14  and (
15    not profile.by_sender().solicited
16    or (
17      profile.by_sender().any_messages_malicious_or_spam
18      and not profile.by_sender().any_false_positives
19    )
20  )
21  
22  // negate highly trusted sender domains unless they fail DMARC authentication
23  and (
24    (
25      sender.email.domain.root_domain in $high_trust_sender_root_domains
26      and not headers.auth_summary.dmarc.pass
27    )
28    or sender.email.domain.root_domain not in $high_trust_sender_root_domains
29  )  
30attack_types:
31  - "Credential Phishing"
32  - "Malware/Ransomware"
33tactics_and_techniques:
34  - "Open redirect"
35detection_methods:
36  - "Sender analysis"
37  - "URL analysis"
38id: "860e1381-a99a-5b6e-bfed-ef0931e06fc7"