Synopsis
Description
A user configured an Exchange inbox rule that may be used to hide emails.
Attacker's Goals
Prevent an organization from warning users that they've been compromised (e.g. an internal spear-phishing campaign).
Investigative actions
- Look for signs that the user account and mailbox are compromised (e.g. abnormal logins, unusual activity).
- Check if the rule keywords look suspicious.
- 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 multiple instances of email hiding, which may be an indication of a larger campaign.
- Check if the user regularly configures inbox rules.
Variations
Possible BEC Exchange email-hiding inbox rule
Synopsis
Description
A user configured an Exchange inbox rule that may be used to hide emails. The rule contains characteristics that resemble a business email compromise (BEC) attack.
Attacker's Goals
Prevent an organization from warning users that they've been compromised (e.g. an internal spear-phishing campaign).
Investigative actions
- Look for signs that the user account and mailbox are compromised (e.g. abnormal logins, unusual activity).
- Check if the rule keywords look suspicious.
- 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 multiple instances of email hiding, which may be an indication of a larger campaign.
- Check if the user regularly configures inbox rules.
Suspicious Exchange email-hiding inbox rule
Synopsis
Description
A user configured an Exchange inbox rule that may be used to hide emails. The rule hides emails that contain suspicious keywords, which may be a sign of a compromised account.
Attacker's Goals
Prevent an organization from warning users that they've been compromised (e.g. an internal spear-phishing campaign).
Investigative actions
- Look for signs that the user account and mailbox are compromised (e.g. abnormal logins, unusual activity).
- Check if the rule keywords look suspicious.
- 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 multiple instances of email hiding, which may be an indication of a larger campaign.
- Check if the user regularly configures inbox rules.
Abnormal Exchange email-hiding inbox rule
Synopsis
Description
A user configured an Exchange inbox rule that may be used to hide emails.
Attacker's Goals
Prevent an organization from warning users that they've been compromised (e.g. an internal spear-phishing campaign).
Investigative actions
- Look for signs that the user account and mailbox are compromised (e.g. abnormal logins, unusual activity).
- Check if the rule keywords look suspicious.
- 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 multiple instances of email hiding, which may be an indication of a larger campaign.
- Check if the user regularly configures inbox rules.