Open redirect: fenc.com

 1name: "Open redirect: fenc.com"
 2description: |
 3    Message contains use of the fenc.com open 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.root_domain == "fenc.com"
10          and .href_url.path =~ "/redirector.aspx"
11          and regex.icontains(.href_url.query_params,
12                              'y=(?:https?|(?:\/|%2f)(?:\/|%2f))'
13          )
14          and not regex.icontains(.href_url.query_params, 'y=[^\&]*fenc\.com')
15  )
16  and not sender.email.domain.root_domain == "fenc.com"
17  
18  // negate highly trusted sender domains unless they fail DMARC authentication
19  and (
20    (
21      sender.email.domain.root_domain in $high_trust_sender_root_domains
22      and not headers.auth_summary.dmarc.pass
23    )
24    or sender.email.domain.root_domain not in $high_trust_sender_root_domains
25  )  
26attack_types:
27  - "Credential Phishing"
28  - "Malware/Ransomware"
29tactics_and_techniques:
30  - "Open redirect"
31detection_methods:
32  - "Sender analysis"
33  - "URL analysis"
34id: "6ff1ab52-70e2-5135-8715-a3b1cc57e10f"