Possible multistage attack in Microsoft Teams

Synopsis

Field	Value
Activation Period	14 Days
Training Period	30 Days
Test Period	12 Hours
Deduplication Period	1 Day
Required Data	Office 365 Audit
Detection Modules	Identity Threat Module
Detector Tags	Microsoft Teams
ATT&CK Tactic	Initial Access (TA0001)
ATT&CK Technique	Phishing (T1566)
Severity	Low

Description

Possible multistage attack in Microsoft Teams.

Attacker's Goals

Attackers may leverage Microsoft Teams to conduct phishing attacks by exploiting trusted communication channels with users inside the organization.

Investigative actions

• Verify the suspicious activity to validate the legitimacy of the user's actions.
• Review Teams chat logs and meeting invites for interactions with external tenants, focusing on unusual file sharing or unsolicited links.
• Hunt for known phishing indicators (suspicious domains, URL patterns, or IPs) in the Teams messages and linked content.
• Evaluate the external tenant reputation.
• Check for anomalous MS Teams actions like suspicious application installation, message extraction, policy changes or internal spear phishing attempts linked to the user post-login.
• Follow further actions done by the account.

Variations

Malicious activity had been detected with strong indicators

Synopsis

Field	Value
ATT&CK Tactic	Initial Access (TA0001)
ATT&CK Technique	Phishing (T1566)
Severity	Medium

Description

Malicious Microsoft Teams activity detected across multiple indicators, the activities have strong indications of a malicious action.

Attacker's Goals

Attackers may leverage Microsoft Teams to conduct phishing attacks by exploiting trusted communication channels with users inside the organization.

Investigative actions

• Verify the suspicious activity to validate the legitimacy of the user's actions.
• Review Teams chat logs and meeting invites for interactions with external tenants, focusing on unusual file sharing or unsolicited links.
• Hunt for known phishing indicators (suspicious domains, URL patterns, or IPs) in the Teams messages and linked content.
• Evaluate the external tenant reputation.
• Check for anomalous MS Teams actions like suspicious application installation, message extraction, policy changes or internal spear phishing attempts linked to the user post-login.
• Follow further actions done by the account.