Open redirect: embluemail.com

 1name: "Open redirect: embluemail.com"
 2description: |
 3    Message contains use of the embluemail.com redirect. 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 == "nts.embluemail.com"
10          and strings.istarts_with(.href_url.path, '/p/cl')
11          and strings.icontains(.href_url.query_params, '!')
12          and regex.icontains(.href_url.query_params,
13                              '\!(?:((?:%68|h)(?:%74|t){2}(?:%70|p)(?:%73|s)?)?(?:%3a|:))?(?:%2f|\/){2}'
14          )
15  )
16  and not sender.email.domain.domain == "nts.embluemail.com"
17  and not strings.iends_with(headers.message_id, '@embluemail.com>')
18  
19  // negate highly trusted sender domains unless they fail DMARC authentication
20  and not (
21    sender.email.domain.root_domain in $high_trust_sender_root_domains
22    and coalesce(headers.auth_summary.dmarc.pass, false)
23  )  
24attack_types:
25  - "Credential Phishing"
26  - "Malware/Ransomware"
27tactics_and_techniques:
28  - "Open redirect"
29detection_methods:
30  - "Sender analysis"
31  - "URL analysis"
32id: "48c5abd3-4f3f-5a3f-8bc0-cbba10d901e6"