Detections
Explore public detection logic contributed by the community across SIEM and rule languages.
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This rule detects potential internal phishing campaigns by identifying newly observed sender domains that send emails to a large number of internal recipients within a short period. It looks for sender domains that have been seen for the first time within the last 7 days, have sent emails to more than 10 unique recipients, and have sent more than 5 emails in total. This behavior can indicate an attacker attempting to phish internal users from a newly created or compromised domain.
Detects creation of malicious inbox rules via Exchange Web Services for persistence
This rule detects when a user creates two or more email forwarding rules within a one-hour period in Exchange Online. This behavior can indicate an adversary setting up persistence or exfiltration mechanisms for email.
Detects creation of email auto-forwarding rules for persistent email collection
This rule detects a high volume of successful sign-in attempts to Exchange Online from a single IP address where the UserPrincipalName ends with '@' (indicating an anonymous or malformed UPN) and Conditional Access was not applied. This pattern can be indicative of anonymous SMTP relay abuse, often used for spamming or phishing campaigns.
Detects the creation or modification of inbox rules that forward or redirect emails to another recipient. This can be an indicator of an adversary attempting to exfiltrate emails or maintain persistence.
This rule detects the creation of new transport rules within Exchange Online. Adversaries may create malicious transport rules to forward emails, bypass security controls, or exfiltrate data. Monitoring the creation of new transport rules can help identify suspicious activity.
This rule detects the creation of an email auto-forwarding rule within Microsoft Exchange via the Exchange Web Services (EWS) interface. It specifically looks for HTTP requests to the '/EWS/Exchange.asmx' endpoint containing the string 'ForwardToRecipients' in the client body, indicating an attempt to configure email forwarding.
This rule detects internal SMTP traffic that contains both 'Content-Type: application/' and 'filename=' in the email body. This combination is often indicative of an attachment being sent, and in the context of 'Lateral Phishing' (T1534), it suggests an attempt to send malicious attachments internally. The rule is set to trigger an alert if 5 such events occur from the same source IP within 300 seconds, indicating a potential automated or high-volume internal phishing attempt.
Detects a successful login from a non-compliant, unmanaged device followed by an inbox rule creation or modification within 10 minutes. This sequence aligns with post-compromise evasion tactics observed in device code phishing campaigns like Kali365, where attackers quickly suppress security alerts after gaining access.
Detects Microsoft Teams messages containing links to Pastebin. Threat actors (e.g., Nimbus RAT operators) use Pastebin to host instruction checklists and payload URLs during vishing attacks.
This rule detects potential 'reply-all' storm attacks or malicious mass emails sent to large distribution lists within the organization. It identifies emails sent to 50 or more recipients where the subject line contains phrases like 'reply all' or 'all members', originating from an internal company domain. The rule then counts such broadcast emails within one-hour bins to identify unusual activity.
This rule detects potential internal phishing campaigns by identifying newly observed sender domains that send emails to a large number of internal recipients within a short period. It looks for sender domains that have been seen for the first time within the last 7 days, have sent emails to more than 10 unique recipients, and have sent more than 5 emails in total. This behavior can indicate an attacker attempting to phish internal users from a newly created or compromised domain.
Detects the creation of email forwarding rules in Google Workspace that direct emails to external domains. This activity can indicate potential Business Email Compromise (BEC) for persistence or insider data exfiltration.
This rule detects potential 'reply-all' storm attacks or malicious mass emails sent to large distribution lists within the organization. It identifies emails sent to 50 or more recipients where the subject line contains phrases like 'reply all' or 'all members', originating from an internal company domain. The rule then counts such broadcast emails within one-hour bins to identify unusual activity.
This rule detects the creation or modification of Exchange transport rules or inbox rules that forward or redirect emails to external domains. It specifically looks for operations like 'New-TransportRule', 'Set-TransportRule', 'New-InboxRule', 'Set-InboxRule', 'Set-Mailbox', 'UpdateInboxRules', and 'Set-TransportConfig' where the destination is an email address outside of the organization's verified domains. This activity can indicate data exfiltration or an attempt to maintain persistence and collect sensitive information.
KQL Query from file: Email Bombing and Teams Impersonation Detection
High Email Volume to Personal Accounts
Cortex XDR
Detects potential data exfiltration or policy violation by identifying users sending a high volume of emails, large emails, or emails to many unique personal email addresses (e.g., Gmail, Yahoo, Outlook.com) from an Office 365 Exchange Online mailbox. This rule aggregates email activity by sender and flags if any of the defined thresholds are met: total sent data to personal addresses exceeds 25 MB, total messages sent to personal addresses exceeds 10, emails sent to more than 5 unique personal addresses, or any single message sent to a personal address exceeds 25 MB. This is designed to be ran as a scheduled correlation for a day time frame. Thresholds can also be configured to fit your environment. Each user will have a different line that contains all of the matching emails they sent to, the attachments, and subjects of the emails.
High Email Volume to Personal Accounts
Cortex XDR
Detects potential data exfiltration or policy violation by identifying users sending a high volume of emails, large emails, or emails to many unique personal email addresses (e.g., Gmail, Yahoo, Outlook.com) from an Office 365 Exchange Online mailbox. This rule aggregates email activity by sender and flags if any of the defined thresholds are met: total sent data to personal addresses exceeds 25 MB, total messages sent to personal addresses exceeds 10, emails sent to more than 5 unique personal addresses, or any single message sent to a personal address exceeds 25 MB. This is designed to be ran as a scheduled correlation for a day time frame. Thresholds can also be configured to fit your environment. Each user will have a different line that contains all of the matching emails they sent to, the attachments, and subjects of the emails.
This rule detects the creation or modification of Exchange inbox rules with highly suspicious or obfuscated names. Adversaries often create inbox rules with short, non-descriptive, or special character names (e.g., '.', '...', ';') to forward, redirect, or delete emails, facilitating data exfiltration or maintaining persistence. The rule specifically looks for rule names that are very short (less than 3 characters), empty, or match a predefined list of suspicious names.
Detects the creation or modification of Exchange Online inbox rules, transport rules, or mailbox settings where the rule name consists exclusively of special characters. This pattern can be indicative of malicious activity, such as an attacker attempting to hide a forwarding rule or other automated action by using an obscure name.
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