Brand impersonation: Microsoft

  1name: "Brand impersonation: Microsoft"
  2description: |
  3    Impersonation of the Microsoft brand.
  4references:
  5  - "https://www.itproportal.com/news/cybercriminals-launch-targeted-phishing-attacks-against-microsoft-365-users/"
  6  - "https://cofense.com/blog/office-365-phishing-variant/"
  7  - "https://www.helpnetsecurity.com/2020/05/04/fake-microsoft-teams-notification/"
  8type: "rule"
  9severity: "high"
 10authors:
 11  - twitter: "amitchell516"
 12source: |
 13  type.inbound
 14  and (
 15    length(body.links) < 30
 16    or sender.email.local_part == "newsletter" and length(body.links) < 5
 17  )
 18  and (
 19    (
 20      strings.ilike(subject.subject, '*Microsoft 365*')
 21      and strings.ilike(subject.subject, '*is expired*')
 22    )
 23    or (
 24      // should catch any instance of the word "expired"
 25      strings.ilike(body.current_thread.text, "*expir*")
 26      and strings.ilike(body.current_thread.text, "*password*")
 27      and strings.ilike(body.current_thread.text, "*microsoft*")
 28    )
 29    or regex.icontains(body.current_thread.text,
 30                       ".*reach you.{0,20}Microsoft Teams",
 31                       "microsoft account\n2fa"
 32    )
 33    or strings.icontains(body.current_thread.text, "microsoft account team")
 34    or strings.ilike(sender.display_name, '*new activity in Teams*')
 35    or strings.icontains(strings.replace_confusables(sender.display_name),
 36                         'microsoft advertising support'
 37    )
 38    or subject.subject =~ 'Offline Message in Teams'
 39    or strings.ilike(subject.subject, '*Teams Sent A Message')
 40    or sender.display_name in~ (
 41      'Microsoft Partner Network',
 42      'Microsoft Advertising',
 43      'Microsoft',
 44      'Microsoft Feedback',
 45      'Microsoft account team',
 46      'Microsoft Support',
 47      'Microsoft 365 Message center',
 48      'Microsoft Azure'
 49    )
 50    or regex.icontains(sender.display_name,
 51                       "[MḾṀṂⱮМḿṁṃᵯⱮ𝐌𝑀][iíìîïīĭĩįıɪɨᵢⁱ𝐢𝑖][cćĉċčçƈȼ𝐜𝑐][rŕŗřȑȓɾᵣⁿʳ𝐫𝑟][oóòôõöøōŏőɵₒᵒº𝐨𝑜][sśŝšșşʂᵴˢˢ𝐬𝑠][oóòôõöøōŏőɵₒᵒº𝐨𝑜][fḟƒᵮᶠ𝐟𝑓][tťțţᵵₜᵗᵗ𝐭𝑡]"
 52    )
 53    or regex.icontains(sender.display_name,
 54                       "[MḾṀṂⱮМḿṁṃᵯⱮ𝐌𝑀][iíìîïīĭĩįıɪɨᵢⁱ𝐢𝑖][rŕŗřȑȓɾᵣⁿʳ𝐫𝑟][cćĉċčçƈȼ𝐜𝑐][oóòôõöøōŏőɵₒᵒº𝐨𝑜][sśŝšșşʂᵴˢˢ𝐬𝑠][oóòôõöøōŏőɵₒᵒº𝐨𝑜][fḟƒᵮᶠ𝐟𝑓][tťțţᵵₜᵗᵗ𝐭𝑡]" // [sic]
 55    )
 56    or any(attachments,
 57           .file_extension == "pdf"
 58           and beta.parse_exif(.).page_count == 1
 59           and any(ml.logo_detect(.).brands, .name == "Microsoft")
 60           and any(file.explode(.),
 61                   regex.icontains(.scan.ocr.raw, '[©@]\s*(?:\d+)?\s*Microsoft')
 62           )
 63    )
 64  )
 65  and not (
 66    sender.email.domain.root_domain in~ (
 67      'microsoft.com',
 68      'microsoftstoreemail.com',
 69      'microsoftsupport.com',
 70      'office.com',
 71      'teams-events.com',
 72      'qualtrics-research.com',
 73      'skype.com',
 74      'azureadnotifications.us',
 75      'microsoftonline.us',
 76      'mail.microsoft',
 77      'office365.com',
 78      'microsoftadvertising.com'
 79    )
 80    and headers.auth_summary.dmarc.pass
 81  )
 82  and not (
 83    sender.email.domain.domain in~ (
 84      'microsoft.regsvc.com',
 85      'microsoft.onmicrosoft.com'
 86    )
 87    and headers.auth_summary.dmarc.pass
 88  )
 89  and (
 90    profile.by_sender().prevalence in ("new", "outlier")
 91    or (
 92      profile.by_sender().any_messages_malicious_or_spam
 93      and not profile.by_sender().any_messages_benign
 94    )
 95  )
 96  
 97  // negate legitimate Office 365 bouncebacks
 98  and not (
 99    all(attachments,
100        .content_type in ("message/delivery-status", "message/rfc822")
101    )
102    and (
103      sender.email.local_part in ('postmaster', 'mailer-daemon')
104      or strings.starts_with(sender.email.local_part, 'microsoftexchange')
105    )
106    and (
107      strings.contains(subject.subject, 'Undeliverable:')
108      or strings.contains(subject.subject, 'Blocked:')
109      or strings.contains(subject.subject, 'Não é possível entregar:')
110      or strings.contains(subject.subject, 'Nie można dostarczyć:')
111      or strings.contains(subject.subject, 'Non remis :')
112      or strings.contains(subject.subject, 'Teslim edilmez:')
113      or strings.contains(subject.subject, 'No se puede entregar:')
114    )
115  )
116  
117  // negate other legitimate MS notifications
118  and not (
119    length(body.links) > 0
120    and (
121      (
122        all(body.links,
123            .href_url.domain.root_domain in (
124              "aka.ms",
125              "microsoftonline.com",
126              "microsoft.com"
127            )
128            or .href_url.domain.tld == "microsoft"
129        )
130        and headers.auth_summary.dmarc.pass
131      )
132  
133      // microsoft b2b applications invitations - no auth checks
134      or (
135        sender.email.local_part == "invites"
136        and sender.email.domain.root_domain == "onmicrosoft.com"
137        // infra validated message id
138        and strings.icontains(headers.message_id, "pepf")
139      )
140    )
141  )
142  
143  // negate highly trusted sender domains unless they fail DMARC authentication
144  and not (
145    sender.email.domain.root_domain in $high_trust_sender_root_domains
146    and coalesce(headers.auth_summary.dmarc.pass, false)
147  )
148  // not a newsletter or advertisement
149  and not (
150    any(ml.nlu_classifier(body.current_thread.text).topics,
151        .name in ("Newsletters and Digests") and .confidence == "high"
152    )
153    and (
154      any(body.links,
155          strings.icontains(.display_text, "unsubscribe")
156          and (strings.icontains(.href_url.path, "unsubscribe"))
157      )
158    )
159  )  
160
161attack_types:
162  - "Credential Phishing"
163tactics_and_techniques:
164  - "Impersonation: Brand"
165  - "Social engineering"
166detection_methods:
167  - "Content analysis"
168  - "Sender analysis"
169id: "6e2f04e6-b607-5e36-9015-d39c98265579"