Brand impersonation: SendGrid

  1name: "Brand impersonation: SendGrid"
  2description: "Detects inbound messages that impersonate Twilio/SendGrid through display name or domain manipulation, combined with security or authentication-themed content, while failing authentication checks and originating from untrusted sources."
  3type: "rule"
  4severity: "medium"
  5source: |
  6  type.inbound
  7  and (
  8    (
  9      // SendGrid impersonation patterns
 10      strings.ilike(strings.replace_confusables(sender.display_name),
 11                    '*sendgrid*'
 12      )
 13      or strings.ilevenshtein(strings.replace_confusables(sender.display_name),
 14                              'sendgrid'
 15      ) <= 1
 16      or (
 17        strings.ilike(strings.replace_confusables(sender.email.local_part),
 18                      '*sendgrid*'
 19        )
 20        and (
 21          sender.display_name is null
 22          or strings.ilike(strings.replace_confusables(subject.base),
 23                           '*sendgrid*'
 24          )
 25        )
 26      )
 27      or any(ml.logo_detect(file.message_screenshot()).brands,
 28             .name == "SendGrid" and .confidence == "high"
 29      )
 30    )
 31    or (
 32      // Twilio impersonation patterns
 33      strings.ilike(strings.replace_confusables(sender.display_name), '*twilio*')
 34      or strings.ilevenshtein(strings.replace_confusables(sender.display_name),
 35                              'twilio'
 36      ) <= 1
 37      or (
 38        strings.ilike(strings.replace_confusables(sender.email.local_part),
 39                      '*twilio*'
 40        )
 41        and (
 42          sender.display_name is null
 43          or strings.ilike(strings.replace_confusables(subject.base), '*twilio*')
 44        )
 45      )
 46    )
 47    or strings.icontains(body.current_thread.text, "the sendgrid team")
 48    or 2 of (
 49      regex.icontains(body.current_thread.text, '(?:Twilio|SendGrid)'),
 50      strings.icontains(body.current_thread.text, '1801 California St'),
 51      strings.icontains(body.current_thread.text, 'Denver, CO 80202')
 52    )
 53    // SendGrid content from non-SendGrid marketing platforms
 54    or (
 55      sender.email.domain.root_domain in (
 56        "selfcast.com",
 57        "mailchimp.com",
 58        "constantcontact.com",
 59        "hubspot.com",
 60        "klaviyo.com",
 61        "mailgun.com"
 62      )
 63      and (
 64        (
 65          (
 66            strings.icontains(body.current_thread.text, "sendgrid")
 67            or strings.icontains(subject.base, "sendgrid")
 68          )
 69          and 3 of (
 70            strings.icontains(body.current_thread.text, "webhook"),
 71            strings.icontains(body.current_thread.text, "endpoint"),
 72            strings.icontains(body.current_thread.text, "api"),
 73            strings.icontains(body.current_thread.text, "delivery"),
 74            strings.icontains(body.current_thread.text, "event notification")
 75          )
 76        )
 77        and (
 78          // Look for SendGrid-related content with non-SendGrid tracking links
 79          any(body.links,
 80              strings.icontains(.href_url.url, "selfcast.com")
 81              or (
 82                .display_url.url is not null
 83                and strings.icontains(.display_url.url, "sendgrid.com")
 84              )
 85          )
 86        )
 87      )
 88    )
 89  )
 90  and (
 91    // Content analysis using ML/NLU
 92    any(ml.nlu_classifier(body.current_thread.text).topics,
 93        .name in (
 94          "Security and Authentication",
 95          "Secure Message",
 96          "Reminders and Notifications",
 97          "Software and App Updates",
 98          "Customer Service and Support"
 99        )
100        and .confidence in ("medium", "high")
101    )
102    or any(ml.nlu_classifier(beta.ocr(file.message_screenshot()).text).topics,
103           .name in (
104             "Security and Authentication",
105             "Secure Message",
106             "Reminders and Notifications",
107             "Software and App Updates",
108             "Customer Service and Support"
109           )
110           and .confidence in ("medium", "high")
111    )
112    or any(ml.nlu_classifier(body.current_thread.text).intents,
113           .name == "cred_theft" and .confidence == "high"
114    )
115    or any(ml.nlu_classifier(beta.ocr(file.message_screenshot()).text).intents,
116           .name == "cred_theft" and .confidence == "high"
117    )
118  
119    // any capacity or limits mentioned
120    or any([subject.base, body.current_thread.text],
121           (strings.icontains(., "capacity") or strings.icontains(., "limit"))
122           and regex.icontains(., '\breach(?:\b|ed)')
123    )
124  )
125  
126  // and the sender is not in org_domains or from sendgrid domains and passes auth
127  and not (
128    sender.email.domain.valid
129    and (
130      sender.email.domain.root_domain in $org_domains
131      or (
132        sender.email.domain.root_domain in (
133          "sendgrid.com",
134          "sendgrid.net",
135          "twilio.com",
136          "swoogo.com", // events planning software used by Twillio
137          "sendsafely.com", // secure delivery used by Twillio
138          "evolve.com", // same address as Twillio
139          "sendgridsolutions.com"
140        )
141      )
142    )
143    and headers.auth_summary.dmarc.pass
144  )
145  // Exclude high trust domains with valid auth and solicited senders
146  and (
147    (
148      sender.email.domain.root_domain in $high_trust_sender_root_domains
149      and not headers.auth_summary.dmarc.pass
150    )
151    or sender.email.domain.root_domain not in $high_trust_sender_root_domains
152  )
153  and not profile.by_sender().solicited  
154attack_types:
155  - "BEC/Fraud"
156  - "Credential Phishing"
157  - "Spam"
158tactics_and_techniques:
159  - "Impersonation: Brand"
160  - "Social engineering"
161detection_methods:
162  - "Content analysis"
163  - "Header analysis"
164  - "Natural Language Understanding"
165  - "Optical Character Recognition"
166  - "Sender analysis"
167id: "d800124f-6aa4-58e1-8fa7-beec4958924f"