Outbound email to an address hosted by a public email service provider

Synopsis

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

Description

Internal sender emailed to an address hosted by a public email service provider.

Attacker's Goals

• Extracting valuable information outside the company.

Investigative actions

• Check the content of the email that was sent.
• Review the external recipient address and assess its reputation.
• Review past emails sent from this mailbox for any suspicious activity.
• Check for unusual emails sent to this recipient's address.
• Monitor further action taken, such as accessing to private keys, API tokens and sensitive data.

Variations

Outbound email to a single address hosted by a public email service provider

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

Internal sender emailed to a single recipient with public email service provider.

Attacker's Goals

• Extracting valuable information outside the company.

Investigative actions

• Check the content of the email that was sent.
• Review the external recipient address and assess its reputation.
• Review past emails sent from this mailbox for any suspicious activity.
• Check for unusual emails sent to this recipient's address.
• Monitor further action taken, such as accessing to private keys, API tokens and sensitive data.