Exchange inbox forwarding rule configured

Synopsis

Field	Value
Activation Period	14 Days
Training Period	30 Days
Test Period	N/A (single event)
Deduplication Period	1 Day
Required Data	Office 365 Audit
Detection Modules	Identity Threat Module, SaaS Threat Detection, Email
ATT&CK Tactic	Collection (TA0009), Exfiltration (TA0010)
ATT&CK Technique	Email Collection: Email Forwarding Rule (T1114.003), Automated Exfiltration (T1020), Email Collection (T1114)
Severity	Informational

Description

A user configured an Exchange inbox forwarding rule, which forwards emails that meet specific conditions.

Attacker's Goals

Create an inbox rule using a compromised user account to automatically forward emails containing specific conditions to an external recipient.

Investigative actions

• Check what conditions are met in the inbox rule (e.g. specific keywords in the subject or body).
• Determine if any of the conditions and keywords look suspicious.
• Look for signs that the user account and mailbox are compromised (e.g. abnormal logins, unusual activity).
• Check if the forwarding domain is an unknown external domain and look up its reputation.
• Investigate the IP address associated with the rule.
• Follow further actions done by the account.
• Check for a possible phishing campaign on the organization.
• Look for emails sent to this recipient by other users.

Variations

Exchange inbox forwarding rule configured by a delegate user

Synopsis

Field	Value
ATT&CK Tactic	Collection (TA0009), Exfiltration (TA0010)
ATT&CK Technique	Email Collection: Email Forwarding Rule (T1114.003), Automated Exfiltration (T1020), Email Collection (T1114)
Severity	Informational

Description

A user configured an Exchange inbox forwarding rule, which forwards emails that meet specific conditions. The user who set the forwarding is a delegated user, who performed this action on behalf of another user.

Attacker's Goals

Create an inbox rule using a compromised user account to automatically forward emails containing specific conditions to an external recipient.

Investigative actions

• Check what conditions are met in the inbox rule (e.g. specific keywords in the subject or body).
• Determine if any of the conditions and keywords look suspicious.
• Look for signs that the user account and mailbox are compromised (e.g. abnormal logins, unusual activity).
• Check if the forwarding domain is an unknown external domain and look up its reputation.
• Investigate the IP address associated with the rule.
• Follow further actions done by the account.
• Check for a possible phishing campaign on the organization.
• Look for emails sent to this recipient by other users.

Suspicious Exchange inbox forwarding rule configured

Synopsis

Field	Value
ATT&CK Tactic	Collection (TA0009), Exfiltration (TA0010)
ATT&CK Technique	Email Collection: Email Forwarding Rule (T1114.003), Automated Exfiltration (T1020), Email Collection (T1114)
Severity	Medium

Description

A user configured an Exchange inbox forwarding rule, which forwards emails that meet specific conditions.

Attacker's Goals

Create an inbox rule using a compromised user account to automatically forward emails containing specific conditions to an external recipient.

Investigative actions

• Check what conditions are met in the inbox rule (e.g. specific keywords in the subject or body).
• Determine if any of the conditions and keywords look suspicious.
• Look for signs that the user account and mailbox are compromised (e.g. abnormal logins, unusual activity).
• Check if the forwarding domain is an unknown external domain and look up its reputation.
• Investigate the IP address associated with the rule.
• Follow further actions done by the account.
• Check for a possible phishing campaign on the organization.
• Look for emails sent to this recipient by other users.

External Exchange inbox forwarding rule configured

Synopsis

Field	Value
ATT&CK Tactic	Collection (TA0009), Exfiltration (TA0010)
ATT&CK Technique	Email Collection: Email Forwarding Rule (T1114.003), Automated Exfiltration (T1020), Email Collection (T1114)
Severity	Low

Description

A user configured an Exchange inbox forwarding rule, which forwards emails that meet specific conditions. The rule forwards emails to a public domain, which may be a sign of compromise.

Attacker's Goals

Create an inbox rule using a compromised user account to automatically forward emails containing specific conditions to an external recipient.

Investigative actions

• Check what conditions are met in the inbox rule (e.g. specific keywords in the subject or body).
• Determine if any of the conditions and keywords look suspicious.
• Look for signs that the user account and mailbox are compromised (e.g. abnormal logins, unusual activity).
• Check if the forwarding domain is an unknown external domain and look up its reputation.
• Investigate the IP address associated with the rule.
• Follow further actions done by the account.
• Check for a possible phishing campaign on the organization.
• Look for emails sent to this recipient by other users.