Exchange user mailbox forwarding

Cortex XDR Analytics Alert Reference by Alert name
Product
Cortex XDR
Last date published
2024-10-08
Category
Analytics Alert Reference
Order
Alert name

Synopsis

Activation Period

14 Days

Training Period

30 Days

Test Period

N/A (single event)

Deduplication Period

1 Day

Required Data

  • Requires:
    • Office 365 Audit

Detection Modules

Identity Threat Module

Detector Tags

ATT&CK Tactic

ATT&CK Technique

Severity

Low

Description

A user configured Exchange SMTP forwarding on a mailbox, which forwards all emails sent to that mailbox to a specified recipient.

Attacker's Goals

Leverage a compromised user account to modify a mailbox's settings to forward emails to an external recipient and collect sensitive information.

Investigative actions

  • 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.
  • Investigate the IP address associated with the rule.
  • Follow further actions done by the account.

Variations

Exchange user mailbox forwarding by a delegate user

Synopsis

ATT&CK Tactic

ATT&CK Technique

Severity

Informational

Description

A user configured Exchange SMTP forwarding on a mailbox, which forwards all emails sent to that mailbox to a specified recipient. The user who set the forwarding is a delegated user, who performed this action on behalf of another user.

Attacker's Goals

Leverage a compromised user account to modify a mailbox's settings to forward emails to an external recipient and collect sensitive information.

Investigative actions

  • 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.
  • Investigate the IP address associated with the rule.
  • Follow further actions done by the account.


Suspicious Exchange user mailbox forwarding

Synopsis

ATT&CK Tactic

ATT&CK Technique

Severity

Medium

Description

A user configured Exchange SMTP forwarding on a mailbox, which forwards all emails sent to that mailbox to a specified recipient.

Attacker's Goals

Leverage a compromised user account to modify a mailbox's settings to forward emails to an external recipient and collect sensitive information.

Investigative actions

  • 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.
  • Investigate the IP address associated with the rule.
  • Follow further actions done by the account.