Outbound email contains file-sharing service link sent to external recipient

Synopsis

Field	Value
Activation Period	14 Days
Training Period	30 Days
Test Period	N/A (single event)
Deduplication Period	1 Hour 30 Minutes
Required Data	Microsoft 365 Emails
Detection Modules	Email
Detector Tags	Exfiltration
ATT&CK Tactic	Execution (TA0002), Credential Access (TA0006)
ATT&CK Technique	User Execution (T1204), Brute Force: Password Cracking (T1110.002)
Severity	Informational

Description

Identifies outbound emails that include links to file-sharing services sent externally.

Attacker's Goals

Exfiltrate data by sharing a link to a file-sharing service with external recipients, bypassing attachment inspection and potentially evading visibility controls.

Investigative actions

• Review the shared URL to determine if the file is publicly accessible or shared outside the organization.
• Check if the file-sharing domain has been previously used by this sender or others in the organization.
• Investigate recent outbound emails for similar use of file-sharing services or unusual external recipients.

Variations

Outbound email to external recipient(s) uses first-seen for organization file-sharing service

Synopsis

Field	Value
ATT&CK Tactic	Execution (TA0002), Credential Access (TA0006)
ATT&CK Technique	User Execution (T1204), Brute Force: Password Cracking (T1110.002)
Severity	Informational

Description

Identifies outbound emails that include links to file-sharing services sent externally.

Attacker's Goals

Exfiltrate data by sharing a link to a file-sharing service with external recipients, bypassing attachment inspection and potentially evading visibility controls.

Investigative actions

• Review the shared URL to determine if the file is publicly accessible or shared outside the organization.
• Check if the file-sharing domain has been previously used by this sender or others in the organization.
• Investigate recent outbound emails for similar use of file-sharing services or unusual external recipients.

Outbound email to external recipient(s) uses first-seen for sender file-sharing service

Synopsis

Field	Value
ATT&CK Tactic	Execution (TA0002), Credential Access (TA0006)
ATT&CK Technique	User Execution (T1204), Brute Force: Password Cracking (T1110.002)
Severity	Informational

Description

Identifies outbound emails that include links to file-sharing services sent externally.

Attacker's Goals

Exfiltrate data by sharing a link to a file-sharing service with external recipients, bypassing attachment inspection and potentially evading visibility controls.

Investigative actions

• Review the shared URL to determine if the file is publicly accessible or shared outside the organization.
• Check if the file-sharing domain has been previously used by this sender or others in the organization.
• Investigate recent outbound emails for similar use of file-sharing services or unusual external recipients.