Detections
Explore public detection logic contributed by the community across SIEM and rule languages.
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The following analytic identifies the creation of new email forwarding rules in an Office 365 environment via the UpdateInboxRules operation. It leverages Office 365 management activity events to detect rules that forward emails to external recipients by examining the OperationProperties for specific forwarding actions. This activity is significant as it may indicate unauthorized email redirection, potentially leading to data exfiltration. If confirmed malicious, attackers could intercept sensitive communications, leading to data breaches and information leakage.
The following analytic identifies when an O365 email account sends an excessive number of email attachments to external recipients within a short period (within 1 hour). This behavior may indicate a compromised account where the threat actor is attempting to exfiltrate data from the mailbox. Threat actors may attempt to transfer data through email as a simple means of exfiltration from the compromised mailbox. Some account owner legitimate behaviors can trigger this alert, however these actions may not be aligned with organizational expectations / best practice behaviors.
This rule identifies potential data exfiltration attempts where a user sends multiple files (more than 10) from Google Drive as email attachments to free email domains (e.g., gmail.com, aol.com, hotmail.com, outlook.com, icloud.com) within a one-hour window. This behavior can indicate an adversary attempting to move sensitive data out of the organization's controlled environment.
Identifies when a user sends multiple files from Google Drive as an email attachment to a free email domain, which may indicate data exfiltration.
This rule detects the creation or modification of email forwarding or redirection rules within Microsoft 365 audit logs. It specifically looks for operations related to 'UpdateInboxRules', 'Set-Mailbox', 'New-InboxRule', and 'Set-InboxRule' that include parameters indicative of forwarding or redirecting emails, such as 'Forward', 'Recipients', 'ForwardingSmtpAddress', 'ForwardingAddress', 'ForwardAsAttachmentTo', 'ForwardTo', 'RedirectTo', and 'RedirectToRecipients'. This activity can be a sign of an attacker attempting to exfiltrate sensitive information from a compromised mailbox or maintain persistence.
Detects when the Microsoft 365 Security Compliance Center restricts a user from sending email because they exceeded service sending limits. This could indicate a compromised account being used for spamming or other malicious activities, or a legitimate user exceeding limits due to unusual activity.
Detects when Microsoft Cloud App Security reports suspicious email forwarding rules, such as a user creating an inbox rule to forward copies of all emails to an external address. This activity can indicate an attempt to exfiltrate sensitive information.
Detects the usage of the PowerShell `Set-Mailbox` cmdlet to configure an SMTP forwarding rule for a mailbox. This can be indicative of an adversary setting up automatic email forwarding to an external address for data exfiltration or continued access to communications.
Detects when a Security Compliance Center reported a user who exceeded sending limits of the service policies and because of this has been restricted from sending email.
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