Detection rules › Sublime MQL

Brand impersonation: Microsoft Teams

Severity
high
Type
rule
Source
github.com/sublime-security/sublime-rules

Impersonation of a Microsoft Teams message.

Threat classification

Sublime's own taxonomy (not MITRE ATT&CK).

CategoryValues
Attack typesCredential Phishing
Tactics and techniquesImpersonation: Brand, Social engineering

Event coverage

Rule body MQL

type.inbound
and length(filter(attachments,
                  .file_type in $file_types_images or .file_type == "pdf"
           )
) < 10
and any(attachments,
        (.file_type in $file_types_images or .file_type == "pdf")
        and any(file.explode(.),
                regex.icontains(.scan.ocr.raw,
                                "trying to reach you.*microsoft teams"
                )
        )
)
and sender.email.domain.root_domain not in (
  "microsoft.com",
  "microsoftsupport.com",
  "office.com"
)

Detection logic

Scope: inbound message.

Impersonation of a Microsoft Teams message.

  1. inbound message
  2. length(filter(attachments, .file_type in $file_types_images or .file_type == 'pdf')) < 10
  3. any of attachments where all hold:
    • any of:
      • .file_type in $file_types_images
      • .file_type is 'pdf'
    • any of file.explode(.) where:
      • .scan.ocr.raw matches 'trying to reach you.*microsoft teams'
  4. sender.email.domain.root_domain not in ('microsoft.com', 'microsoftsupport.com', 'office.com')

Inspects: attachments[].file_type, sender.email.domain.root_domain, type.inbound. Sensors: file.explode, regex.icontains. Reference lists: $file_types_images.

Indicators matched (5)

FieldMatchValue
attachments[].file_typeequalspdf
regex.icontainsregextrying to reach you.*microsoft teams
sender.email.domain.root_domainmembermicrosoft.com
sender.email.domain.root_domainmembermicrosoftsupport.com
sender.email.domain.root_domainmemberoffice.com