Potential spoofing of internal domain spotted

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	Employee Impersonation, Spear Phishing
ATT&CK Tactic	Initial Access (TA0001), Defense Evasion (TA0005)
ATT&CK Technique	Phishing (T1566), Impersonation (T1656)
Severity	Informational

Description

An external sender is possibly impersonating an employee by spoofing the company's internal address.

Attacker's Goals

• Get credentials for internal systems.
• Executing financial transfers from the company to the attacker's account.
• Extracting information outside the company.
• Encrypting critical information and demanding a ransom.

Investigative actions

• Check the received header path, especially the sender host.
• Check DMARC, SPF AND DKIM authentication results.
• Verify whether the sender's IP address has appeared in different log sources before and its reputation.
• If the message contains attachments or links, scrutinize them for any suspicious indications.
• Monitor further actions taken, such as file downloads or access to potentially malicious links.