sublimemediumRule

Attachment: ICS calendar file with real estate fraud link

Detects calendar files (.ics files) whose parsed event content references real estate transaction documents such as closing disclosures, settlement statements, or 1099-S forms.

MITRE ATT&CK

T1566.002 T1534 T1656 T1566 T1598 T1036 T1027

initial-accessdefense-evasion

Detection Query

type.inbound
and any(attachments,
        (
          .file_type == "ics"
          or .file_extension == "ics"
          or .content_type in ("application/ics", "text/calendar")
        )
        //
        // 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
        //
        and any(beta.file.parse_ics(.).events,
                (
                  any([.summary, .description],
                      regex.icontains(.,
                                      'file attached',
                                      '\brefer\b',
                                      '\brespon(?:d|se)\b',
                                      '\breview\b'
                      )
                  )
                  or any(.links, regex.icontains(.display_text, 'view'))
                )
                and (
                  any([.summary, .description],
                      regex.icontains(., "1099-s", "draw settlement")
                  )
                  or any([.summary, .description],
                         length(.) < 2000
                         and regex.icontains(.,
                                             '(?:attached|buyer/seller|new|preliminary).closing disclosure',
                                             'settlement.(?:&|and.)?(?:report|statement)'
                         )
                  )
                )
        )
)

Data Sources

Email MessagesEmail HeadersEmail Attachments

Platforms

Raw Content

name: "Attachment: ICS calendar file with real estate fraud link"
description: "Detects calendar files (.ics files) whose parsed event content references real estate transaction documents such as closing disclosures, settlement statements, or 1099-S forms."
type: "rule"
severity: "medium"
source: |
  type.inbound
  and any(attachments,
          (
            .file_type == "ics"
            or .file_extension == "ics"
            or .content_type in ("application/ics", "text/calendar")
          )
          //
          // 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
          //
          and any(beta.file.parse_ics(.).events,
                  (
                    any([.summary, .description],
                        regex.icontains(.,
                                        'file attached',
                                        '\brefer\b',
                                        '\brespon(?:d|se)\b',
                                        '\breview\b'
                        )
                    )
                    or any(.links, regex.icontains(.display_text, 'view'))
                  )
                  and (
                    any([.summary, .description],
                        regex.icontains(., "1099-s", "draw settlement")
                    )
                    or any([.summary, .description],
                           length(.) < 2000
                           and regex.icontains(.,
                                               '(?:attached|buyer/seller|new|preliminary).closing disclosure',
                                               'settlement.(?:&|and.)?(?:report|statement)'
                           )
                    )
                  )
          )
  )

attack_types:
  - "BEC/Fraud"
tactics_and_techniques:
  - "Social engineering"
  - "Evasion"
detection_methods:
  - "File analysis"
  - "Content analysis"
  - "URL analysis"
id: "1ff7696f-2e6d-5967-a46c-abf00d7d67a9"