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