Brand impersonation: Microsoft Planner with suspicious link

name: "Brand impersonation: Microsoft Planner with suspicious link"
description: "Impersonation of Microsoft Planner, a component of the Microsoft 365 software suite."
type: "rule"
severity: "medium"
source: |
   type.inbound
   // suspicious link
   and any(body.links,
           (
             .href_url.domain.root_domain not in $tranco_1m
             or .href_url.domain.domain in $free_file_hosts
             or .href_url.domain.root_domain in $free_file_hosts
             or .href_url.domain.root_domain in $free_subdomain_hosts
             or .href_url.domain.domain in $url_shorteners
             or .href_url.domain.domain in $social_landing_hosts
             or .href_url.domain.root_domain in $social_landing_hosts
   
             // mass mailer link, masks the actual URL
             or .href_url.domain.root_domain in (
               "hubspotlinks.com",
               "mandrillapp.com",
               "sendgrid.net",
               "rs6.net"
             )
   
             // Google AMP redirect
             or (
               .href_url.domain.sld == "google"
               and strings.starts_with(.href_url.path, "/amp/")
             )
   
             // Recipient email address in link
             or any(recipients.to,
                    strings.icontains(..href_url.url, .email.email)
                    and .email.domain.valid
             )
             or .href_url.domain.root_domain == "beehiiv.com"
           )
   
           // exclude sources of potential FPs
           and (
             .href_url.domain.root_domain not in (
               "svc.ms",
               "sharepoint.com",
               "1drv.ms",
               "microsoft.com",
               "aka.ms",
               "msftauthimages.net",
               "mimecastprotect.com",
               "office.com",
               "microsoftproject.com"
             )
             or any(body.links, .href_url.domain.domain in $free_file_hosts)
           )
           and .href_url.domain.root_domain not in $org_domains
           and .href_url.domain.valid
           and regex.icontains(.display_text,
                               "(?:go.?to|view|show|display|access|open.?in|review.?on) (teams?|planner|group|task|intranet|discussions?)"
           )
   )
   
   // not a reply
   and (length(headers.references) == 0 or headers.in_reply_to is null)
   
   // Planner logo
   // LogoDetect coming soon
   and (
     all(attachments,
         .file_type in $file_types_images
         and 
         // small, relatively square image
         //
         // This rule makes use of a beta feature and is subject to change without notice
         // using the beta feature in custom rules is not suggested until it has been formally released
         //
         (
           beta.parse_exif(.).image_height / beta.parse_exif(.).image_width
         ) > 0.9
         and (beta.parse_exif(.).image_height + beta.parse_exif(.).image_width) < 500
     )
   )
   
   // suspicious content
   and (
     2 of (
       strings.ilike(body.current_thread.text, "*assigned*new team*"),
       strings.ilike(body.current_thread.text, "*Microsoft Office 365*"),
       strings.ilike(body.current_thread.text, "*internal planner*"),
       strings.ilike(body.current_thread.text, "*internal task*"),
       any(recipients.to,
           strings.icontains(body.current_thread.text, .email.domain.sld)
       )
     )
     or (
       any(ml.nlu_classifier(body.current_thread.text).intents,
           .name == "cred_theft" and .confidence in~ ("medium", "high")
       )
     )
     // multiple links, but all the same root domain
     or (
       length(distinct(body.links, .href_url.domain.root_domain)) == 1
       and 2 < length(body.links) < 10
       and all(body.links,
               .href_url.domain.root_domain != sender.email.domain.root_domain
       )
     )
   )
   // skip senders 
   and not (
     headers.auth_summary.dmarc.pass
     and sender.email.domain.root_domain in (
       "bing.com",
       "microsoft.com",
       "microsoftonline.com",
       "microsoftproject.com",
       "microsoftstoreemail.com",
       "microsoftsupport.com",
       "microsoft365.com",
       "office.com",
       "office365.com",
       "onedrive.com",
       "sharepointonline.com",
       "yammer.com",
       "outlign.co"
     )
   )
   
   // negate highly trusted sender domains unless they fail DMARC authentication
   and (
     (
       sender.email.domain.root_domain in $high_trust_sender_root_domains
       and not headers.auth_summary.dmarc.pass
     )
     or sender.email.domain.root_domain not in $high_trust_sender_root_domains
   )
   and (
     not profile.by_sender().solicited
     or (
       profile.by_sender().any_messages_malicious_or_spam
       and not profile.by_sender().any_messages_benign
     )
   )
   and not profile.by_sender().any_messages_benign
   
   // exclude marketing jargon from ms partners
   and not regex.icontains(body.current_thread.text,
                           '(schedul(e|ing)|set up).{0,20}(call|meeting|demo|zoom|conversation|time|tool|discussion)|book.{0,10}(meeting|demo|call|slot|time)|connect.{0,12}(with me|phone|email)|my.{0,10}(calendar|cal)|reserve.{0,10}s[pl]ot|break the ice|want to know more?|miss your chance|if you no longer wish|if you no longer want|if you wish to opt out|low-code (development|approach|solution|journey|platform)|invite.{0,30}(webinar|presentation)'
   )
attack_types:
  - "Credential Phishing"
tactics_and_techniques:
  - "Evasion"
  - "Image as content"
  - "Impersonation: Brand"
  - "Social engineering"
detection_methods:
  - "Content analysis"
  - "Header analysis"
  - "Natural Language Understanding"
  - "Sender analysis"
  - "URL analysis"
id: "ea363c08-479f-5437-9b5d-3d9e07098200"