Service abuse: Evernote link

 1name: "Service abuse: Evernote link"
 2description: "Detects inbound messages containing a link whose effective destination resolves to evernote.com, where the link text uses document-sharing or e-signature language (e.g., view, open, download, review) and the sender is not from evernote.com. The message body is also classified by an NLU model as exhibiting credential theft or business email compromise intent, indicating abuse of Evernote's legitimate hosting infrastructure to deliver malicious content."
 3type: "rule"
 4severity: "low"
 5source: |
 6  type.inbound
 7  // a link whose effective destination is evernote
 8  and any(body.current_thread.links,
 9          (
10            .href_url.domain.root_domain == "evernote.com"
11            or .display_url.domain.root_domain == "evernote.com"
12            or any(.href_url.query_params_decoded["domain"],
13                   strings.iends_with(., "evernote.com")
14            )
15          )
16          and (
17            any(ml.nlu_classifier(.display_text).topics, .name == 'E-Signature')
18            or regex.icontains(.display_text,
19                               '\b(?:view|open|review|access|download|see|shared?)\b[^\n]{0,30}\b(?:document|doc|file|contract|invoice|statement|agreement|draft|attachment|folder)\b'
20            )
21          )
22  )
23  and any(ml.nlu_classifier(body.current_thread.text).intents,
24          .name in ('cred_theft', 'bec') and .confidence != 'low'
25  )
26  and not (
27    sender.email.domain.root_domain == 'evernote.com'
28    and coalesce(headers.auth_summary.dmarc.pass, false)
29  )  
30attack_types:
31  - "Credential Phishing"
32  - "BEC/Fraud"
33tactics_and_techniques:
34  - "Social engineering"
35detection_methods:
36  - "URL analysis"
37  - "Natural Language Understanding"
38id: "72a4e9ba-fd02-5f7b-ac0f-af9b3ae8f35e"