Credential phishing content and link (untrusted sender)

 1name: "Credential phishing content and link (untrusted sender)"
 2description: |
 3  Message contains credential theft language and a link to a credential phishing page from an unknown sender.
 4  We use Link Analysis in aggressive mode to increase our chances of scanning.  
 5type: "rule"
 6severity: "high"
 7source: |
 8  type.inbound
 9  and (
10    any(ml.nlu_classifier(body.current_thread.text).intents,
11        .name == "cred_theft" and .confidence in ("medium", "high")
12    )
13    // embedded in an image attachment
14    // note: don't use message_screenshot() for now
15    // because it's not limited to current_thread and may FP
16    or any(attachments,
17           .file_type in $file_types_images
18           and any(file.explode(.),
19                   any(ml.nlu_classifier(.scan.ocr.raw).intents,
20                       .name == "cred_theft" and .confidence in ("medium", "high")
21                   )
22           )
23    )
24  )
25  and any(body.links,
26          .href_url.domain.root_domain not in ("outlook.com")
27          and .href_url.domain.domain != "play.google.com"
28          and ml.link_analysis(., mode="aggressive").effective_url.domain.domain != "play.google.com"
29          and ml.link_analysis(., mode="aggressive").credphish.disposition == "phishing"
30          and ml.link_analysis(., mode="aggressive").credphish.confidence in (
31            "medium",
32            "high"
33          )
34          and not .href_url.domain.root_domain == "c3reservations.com"
35  )
36  and (
37    (
38      profile.by_sender_email().prevalence in ("new", "outlier")
39      and not profile.by_sender_email().solicited
40    )
41    or (
42      profile.by_sender_email().any_messages_malicious_or_spam
43      and not profile.by_sender_email().any_messages_benign
44    )
45  )
46  
47  // negate docusign 'via' messages
48  and not (
49    any(headers.hops,
50        any(.fields,
51            .name == "X-Api-Host" and strings.ends_with(.value, "docusign.net")
52        )
53    )
54    and strings.contains(sender.display_name, "via")
55  )
56  
57  // negate docusign originated emails
58  and not any(headers.hops,
59              regex.imatch(.received.server.raw, ".+.docusign.(net|com)")
60  )
61  
62  // negate highly trusted sender domains unless they fail DMARC authentication
63  and (
64    (
65      sender.email.domain.root_domain in $high_trust_sender_root_domains
66      and not headers.auth_summary.dmarc.pass
67    )
68    or sender.email.domain.root_domain not in $high_trust_sender_root_domains
69  )  
70
71attack_types:
72  - "Credential Phishing"
73tactics_and_techniques:
74  - "Social engineering"
75detection_methods:
76  - "Computer Vision"
77  - "Sender analysis"
78  - "URL analysis"
79  - "URL screenshot"
80id: "f0c95bb7-afeb-5c8d-a654-74b5e026007f"