sublimemediumRule

Attachment: XLS with legal confidentiality disclaimer

Detects inbound emails with XLS attachments containing a specific legal confidentiality disclaimer string commonly found in corporate email signatures. This pattern may indicate a malicious spreadsheet crafted to appear as a legitimate forwarded business communication, lending false credibility to the attachment.

MITRE ATT&CK

T1566.001 T1204.002 T1486 T1566.002 T1534 T1656 T1566 T1598 T1059.005

initial-accessexecution

Detection Query

type.inbound
and any(attachments,
        (.file_extension in~ ("xls"))
        and any(file.explode(.),
                any(.scan.strings.strings,
                    strings.contains(.,
                                     'The information contained in this transmission and its attachments (an "e-communication") are intended solely for the use of the intended recipient(s) and may contain information that is privileged, confidential, proprietary and/or otherwise protected by work product immunity or other legal rules.'
                    )
                )
        )
)

Data Sources

Email MessagesEmail HeadersEmail Attachments

Platforms

Raw Content

name: "Attachment: XLS with legal confidentiality disclaimer"
description: "Detects inbound emails with XLS attachments containing a specific legal confidentiality disclaimer string commonly found in corporate email signatures. This pattern may indicate a malicious spreadsheet crafted to appear as a legitimate forwarded business communication, lending false credibility to the attachment."
type: "rule"
severity: "medium"
source: |
  type.inbound
  and any(attachments,
          (.file_extension in~ ("xls"))
          and any(file.explode(.),
                  any(.scan.strings.strings,
                      strings.contains(.,
                                       'The information contained in this transmission and its attachments (an "e-communication") are intended solely for the use of the intended recipient(s) and may contain information that is privileged, confidential, proprietary and/or otherwise protected by work product immunity or other legal rules.'
                      )
                  )
          )
  )
attack_types:
  - "Malware/Ransomware"
  - "BEC/Fraud"
tactics_and_techniques:
  - "Social engineering"
  - "Macros"
detection_methods:
  - "File analysis"
  - "Content analysis"
id: "f31995dd-f922-5954-a077-e74c3a3bc287"