Detection rules › Sublime MQL

Sharepoint online with external recipients and external display name

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

An email from Sharepoint Online that was sent to multiple recipients that did not originate from a sender, by display name, in your organization.

Threat classification

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

CategoryValues
Attack typesCredential Phishing, Spam
Tactics and techniquesEvasion

Event coverage

Rule body MQL

type.inbound
and sender.email.email == "no-reply@sharepointonline.com"
and length(recipients.to) > 40 // You may want to adjust this threshold if 40 is too aggressive
and any(recipients.to, .email.domain.domain in $free_email_providers)
and sender.display_name not in $org_display_names

Detection logic

Scope: inbound message.

An email from Sharepoint Online that was sent to multiple recipients that did not originate from a sender, by display name, in your organization.

  1. inbound message
  2. sender.email.email is 'no-reply@sharepointonline.com'
  3. length(recipients.to) > 40
  4. any of recipients.to where:
    • .email.domain.domain in $free_email_providers
  5. sender.display_name not in $org_display_names

Inspects: recipients.to, recipients.to[].email.domain.domain, sender.display_name, sender.email.email, type.inbound. Reference lists: $free_email_providers, $org_display_names.

Indicators matched (1)

FieldMatchValue
sender.email.emailequalsno-reply@sharepointonline.com