Fake email quarantine notification

  1name: "Fake email quarantine notification"
  2description: "Detects phishing messages implying that emails have been delayed or blocked, prompting users to view, release, or delete pending messages."
  3type: "rule"
  4severity: "high"
  5source: |
  6  type.inbound
  7  and length(body.links) < 10
  8  and (
  9    any(ml.nlu_classifier(body.current_thread.text).intents,
 10        .name == "cred_theft" and .confidence == "high"
 11    )
 12    or (
 13      length(body.current_thread.text) < 250
 14      and any(recipients.to,
 15              strings.icontains(body.current_thread.text, .email.domain.sld)
 16              or strings.icontains(body.current_thread.text, .email.local_part)
 17      )
 18    )
 19  )
 20  and not (
 21    length(ml.nlu_classifier(body.current_thread.text).topics) == 1
 22    and any(ml.nlu_classifier(body.current_thread.text).topics,
 23            .name == "Financial Communications" and .confidence != "low"
 24    )
 25  )
 26  and 3 of (
 27    strings.ilike(body.current_thread.text, "*review*"),
 28    strings.ilike(body.current_thread.text, "*incoming*"),
 29    strings.ilike(body.current_thread.text, "*release*"),
 30    strings.ilike(body.current_thread.text, "*quarantine*"),
 31    strings.ilike(body.current_thread.text, "*messages*"),
 32    strings.ilike(body.current_thread.text, "*server error*"),
 33    strings.ilike(body.current_thread.text, "*blocked*"),
 34    strings.ilike(body.current_thread.text, "*prevented*"),
 35    strings.ilike(body.current_thread.text, "*validation*"),
 36    strings.ilike(body.current_thread.text, "*notification*"),
 37    strings.ilike(body.current_thread.text, "*kindly*"),
 38    strings.ilike(body.current_thread.text, "*on hold*"),
 39    strings.ilike(body.current_thread.text, "*held*"),
 40    strings.ilike(body.current_thread.text, "*pending*"),
 41    strings.ilike(body.current_thread.text, "*stuck*"),
 42    strings.like(body.current_thread.text, "* MX *")
 43  )
 44  and (
 45    any(body.links,
 46        regex.icontains(.display_text, "view", "release", "message", "delete", "recover", "SSO", "sign in")
 47    )
 48    or (
 49      length(body.links) < 3
 50      and any(body.links,
 51              any(recipients.to,
 52                  .email.domain.root_domain == ..display_url.domain.root_domain
 53                  and ..mismatched
 54              )
 55      )
 56    )
 57  )
 58  and not any(body.links,
 59              regex.icontains(.display_text,
 60                              "view document",
 61                              "review (&|and) sign document"
 62              )
 63  )
 64  and sender.email.domain.root_domain not in (
 65    "bing.com",
 66    "microsoft.com",
 67    "microsoftonline.com",
 68    "microsoftsupport.com",
 69    "microsoft365.com",
 70    "office.com",
 71    "office365.com",
 72    "onedrive.com",
 73    "sharepointonline.com",
 74    "yammer.com",
 75    "ppops.net"
 76  )
 77  
 78  // negate org domains unless they fail DMARC authentication
 79  and (
 80    (
 81      sender.email.domain.root_domain in $org_domains
 82      and (
 83        not headers.auth_summary.dmarc.pass
 84        // MS quarantine digest emails from an org domain are router "internally" to MS, therefore, there is no authentication information
 85        or not (
 86          headers.auth_summary.dmarc.pass is null
 87          and all(headers.domains,
 88                  .root_domain in ("outlook.com", "office365.com")
 89          )
 90          // typical emails from freemail Outlook accounts are from prod.outlook.com
 91          and strings.ends_with(headers.message_id, "protection.outlook.com>")
 92        )
 93      )
 94    )
 95    or sender.email.domain.root_domain not in $org_domains
 96  )
 97  
 98  // negate highly trusted sender domains unless they fail DMARC authentication
 99  and (
100    (
101      sender.email.domain.root_domain in $high_trust_sender_root_domains
102      and not headers.auth_summary.dmarc.pass
103    )
104    or sender.email.domain.root_domain not in $high_trust_sender_root_domains
105  )
106  and not profile.by_sender().solicited
107  and not profile.by_sender().any_messages_benign  
108
109attack_types:
110  - "Credential Phishing"
111tactics_and_techniques:
112  - "Social engineering"
113detection_methods:
114  - "Content analysis"
115  - "Natural Language Understanding"
116  - "Sender analysis"
117id: "73f26a3d-b7a5-5b85-83e6-45f1b40f78fb"