Credential phishing: Onedrive impersonation

  1name: "Credential phishing: Onedrive impersonation"
  2description: "This rule detects messages impersonating Microsoft's OneDrive service with medium to high credential theft language in the current thread. The subject is inspected for one drive language, with additional checks for free_subdomain hosted links, additional suspicious subject language or suspicious display text language."
  3type: "rule"
  4severity: "high"
  5source: |
  6  type.inbound
  7  // one drive is found in the sender display name or sender local part
  8  and (
  9    (
 10      regex.icontains(sender.display_name, '[0o]ne\s?dr[il1]ve')
 11      or regex.icontains(sender.email.local_part, '[0o]ne\s?dr[il1]ve')
 12      or 0 < strings.ilevenshtein(strings.replace_confusables(sender.display_name),
 13                                  "one?drive"
 14      ) < 2
 15      or any(attachments,
 16             (
 17               regex.icontains(.file_name, '[0o]ne\s?dr[il1]ve')
 18               and not any(file.explode(.),
 19                           any(.scan.exiftool.fields,
 20                               .key == "Model"
 21                               or (
 22                                 .key == "Software"
 23                                 and strings.starts_with(.value, "Android")
 24                               )
 25                           )
 26                           // exclude images taken with mobile cameras and screenshots from Apple
 27                           or any(.scan.exiftool.fields,
 28                                  .key == "DeviceManufacturer"
 29                                  and .value == "Apple Computer Inc."
 30                           )
 31               )
 32             )
 33             // pdf with OneDrive impersonation
 34             or (
 35               .file_type == "pdf"
 36               and any(ml.logo_detect(.).brands, .name == "Microsoft")
 37               and any(file.explode(.),
 38                       any(.scan.strings.strings,
 39                           strings.icontains(., "shared a file")
 40                       )
 41               )
 42             )
 43      )
 44    )
 45    or regex.imatch(strings.replace_confusables(body.current_thread.text),
 46                    '[0o]ne\s?dr[il1]ve.*'
 47    )
 48    // or one drive is in the subject with a freefile host, additional suspicious language, or suspicious display text
 49    or (
 50      regex.icontains(strings.replace_confusables(subject.subject),
 51                      '[0o]ne\s?dr[il1]ve'
 52      )
 53      and (
 54        any(body.links,
 55            .href_url.domain.root_domain in $free_subdomain_hosts
 56            and .href_url.domain.subdomain is not null
 57            and .href_url.domain.subdomain != "www"
 58        )
 59        or regex.contains(subject.subject, '(shared.{0,30}document)')
 60        or any(body.links,
 61               regex.icontains(.display_text,
 62                               "((view|show|access).(?:report|document)|review doc|view doc|view.attached)"
 63               )
 64        )
 65      )
 66    )
 67    or (
 68      any(beta.ml_topic(body.current_thread.text).topics,
 69          .name == "File Sharing and Cloud Services" and .confidence == "high"
 70      )
 71      // more than half of the links with display text contain the keyword "onedrive"
 72      and ratio(filter(body.links, .display_text is not null),
 73                regex.icontains(.display_text, '[0o]ne\s?dr[il1]ve')
 74      ) > 0.5
 75    )
 76  )
 77  
 78  // and body language is med/high confidence cred theft
 79  and (
 80    any(ml.nlu_classifier(body.current_thread.text).intents,
 81        .name == "cred_theft" and .confidence in ("medium", "high")
 82    )
 83    or any(ml.nlu_classifier(beta.ocr(file.message_screenshot()).text).intents,
 84           .name == "cred_theft" and .confidence in ("medium", "high")
 85    )
 86  )
 87  and length(body.links) < 10
 88  and not (
 89    sender.email.domain.root_domain in (
 90      "bing.com",
 91      "microsoft.com",
 92      "microsoftonline.com",
 93      "microsoftsupport.com",
 94      "microsoft365.com",
 95      "office.com",
 96      "onedrive.com",
 97      "sharepointonline.com",
 98      "yammer.com",
 99    )
100    and coalesce(headers.auth_summary.dmarc.pass, false)
101  )
102  
103  // negate highly trusted sender domains unless they fail DMARC authentication
104  and not (
105    sender.email.domain.root_domain in $high_trust_sender_root_domains
106    and coalesce(headers.auth_summary.dmarc.pass, false)
107  )
108  
109  // excludes docusign senders that contain "via" in the display name
110  and not (
111    any(headers.hops,
112        any(.fields,
113            .name == "X-Api-Host" and strings.ends_with(.value, "docusign.net")
114        )
115    )
116    and strings.contains(sender.display_name, "via")
117  )
118  and not profile.by_sender().any_messages_benign  
119attack_types:
120  - "Credential Phishing"
121tactics_and_techniques:
122  - "Free subdomain host"
123  - "Impersonation: Brand"
124  - "Social engineering"
125detection_methods:
126  - "Content analysis"
127  - "Header analysis"
128  - "Natural Language Understanding"
129  - "URL analysis"
130id: "1f990c92-a6d5-5a0b-9462-ac469a8d556e"