Brand impersonation: Microsoft with embedded logo and credential theft language

  1name: "Brand impersonation: Microsoft with embedded logo and credential theft language"
  2description: "This rule detects messages impersonating Microsoft via a logo and contains credential theft language. From a new and unsolicited sender."
  3type: "rule"
  4severity: "high"
  5source: |
  6  type.inbound
  7  and (
  8    (
  9      length(attachments) > 0
 10      and all(attachments,
 11              .file_type in $file_types_images or .file_type == "pdf"
 12      )
 13    )
 14    or length(attachments) == 0
 15  )
 16  and any(ml.logo_detect(file.message_screenshot()).brands,
 17          strings.starts_with(.name, "Microsoft")
 18  )
 19  and (
 20    any(ml.nlu_classifier(body.current_thread.text).intents,
 21        .name == "cred_theft" and .confidence in ("medium", "high")
 22    )
 23    or (
 24      length(body.current_thread.text) == 0
 25      //
 26      // This rule makes use of a beta feature and is subject to change without notice
 27      // using the beta feature in custom rules is not suggested until it has been formally released
 28      //
 29      and any(ml.nlu_classifier(beta.ocr(file.message_screenshot()).text).intents,
 30              .name == "cred_theft" and .confidence in ("medium", "high")
 31      )
 32    )
 33  )
 34  and (
 35    not (
 36      headers.auth_summary.dmarc.pass
 37      and headers.auth_summary.dmarc.details.from.domain in (
 38        "azureadnotifications.us",
 39        "microsoft.com",
 40        "sharepointonline.com",
 41        "cloudappsecurity.com",
 42        "microsoftsupport.com",
 43        "microsoft.onmicrosoft.com",
 44        "yammer.com",
 45        "microsoftrewards.com"
 46      )
 47    )
 48    or headers.auth_summary.dmarc.pass is null
 49    or headers.auth_summary.dmarc.details.from.domain is null
 50  )
 51  and not (
 52    sender.email.domain.domain == "planner.office365.com"
 53    and headers.return_path.email == "noreply@planner.office365.com"
 54    and headers.auth_summary.dmarc.details.from.root_domain == "office365.com"
 55  )
 56  
 57  // Microsoft has some legit onmicrosoft domains...
 58  and not (
 59    sender.email.domain.domain == "microsoft.onmicrosoft.com"
 60    and headers.auth_summary.spf.pass
 61    and all(body.links, .href_url.domain.root_domain == "microsoft.com")
 62  )
 63  
 64  // message is not from sharepoint actual (additional check in case DMARC check above fails to bail out)
 65  and not (
 66    (
 67      strings.ilike(headers.message_id,
 68                    '<Share-*',
 69                    '<MassDelete-*',
 70                    '<FileDeleteAfterExpiration-*',
 71                    '<NotifyOwnerSharedWithExternalUsers*',
 72                    '<OneTimePasscode*'
 73      )
 74      and strings.ends_with(headers.message_id, '@odspnotify>')
 75    )
 76    or (
 77      any(headers.hops,
 78          any(.fields,
 79              .name == "X-Google-Original-Message-ID"
 80              and strings.ilike(.value,
 81                                '<Share-*',
 82                                '<MassDelete-*',
 83                                '<FileDeleteAfterExpiration-*',
 84                                '<NotifyOwnerSharedWithExternalUsers*',
 85                                '<OneTimePasscode*'
 86              )
 87              and strings.ends_with(.value, '@odspnotify>')
 88          )
 89      )
 90    )
 91  )
 92  
 93  // negate legitimate microsoft b2b applications invitations
 94  and not (
 95    length(body.links) > 0
 96    and (
 97      sender.email.local_part == "invites"
 98      and sender.email.domain.root_domain == "onmicrosoft.com"
 99      // infra validated message id
100      and strings.icontains(headers.message_id, "pepf")
101    )
102  )
103  
104  // sender profiles
105  and (
106    not profile.by_sender().solicited
107    or (
108      profile.by_sender().any_messages_malicious_or_spam
109      and not profile.by_sender().any_messages_benign
110    )
111  )
112  
113  // negate org domains unless they fail DMARC authentication
114  and (
115    (
116      sender.email.domain.root_domain in $org_domains
117      and (
118        not headers.auth_summary.dmarc.pass
119        // MS quarantine digest emails from an org domain are router "internally" to MS, therefore, there is no authentication information
120        or not (
121          headers.auth_summary.dmarc.pass is null
122          and all(headers.domains,
123                  .root_domain in ("outlook.com", "office365.com")
124          )
125          // typical emails from freemail Outlook accounts are from prod.outlook.com
126          and strings.ends_with(headers.message_id, "protection.outlook.com>")
127        )
128      )
129    )
130    or sender.email.domain.root_domain not in $org_domains
131  )
132  
133  // negate sharepoint file shares with mimecast rewrites
134  and not (
135    // rewritten message ID
136    strings.iends_with(headers.message_id, 'mimecast.lan>')
137    and all(filter(body.links,
138                   strings.icontains(subject.subject, .display_text)
139                   or .display_text == "Open"
140            ),
141            .href_url.domain.root_domain in (
142              "mimecastprotect.com",
143              "mimecast.com"
144            )
145            and any(.href_url.query_params_decoded["domain"],
146                    strings.parse_domain(.).tld == "ms"
147                    or strings.parse_domain(.).root_domain == "sharepoint.com"
148            )
149    )
150  )
151  
152  // negate highly trusted sender domains unless they fail DMARC authentication
153  and not (
154    sender.email.domain.root_domain in $high_trust_sender_root_domains
155    and coalesce(headers.auth_summary.dmarc.pass, false)
156  )
157  and not profile.by_sender().any_messages_benign  
158
159attack_types:
160  - "Credential Phishing"
161tactics_and_techniques:
162  - "Impersonation: Brand"
163  - "Social engineering"
164detection_methods:
165  - "Computer Vision"
166  - "Natural Language Understanding"
167  - "Sender analysis"
168id: "3ee9ef3d-8ec4-5df0-a8a2-5c6d037eb17a"