Detections
Explore public detection logic contributed by the community across SIEM and rule languages.
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The following analytic identifies user sessions in Office 365 accessed from multiple IP addresses, indicating potential adversary-in-the-middle (AiTM) phishing attacks. It detects this activity by analyzing Azure Active Directory logs for 'UserLoggedIn' operations and flags sessions with more than one associated IP address. This behavior is significant as it suggests unauthorized concurrent access, which is uncommon in normal usage. If confirmed malicious, the impact could include data theft, account takeover, and the launching of internal phishing campaigns, posing severe risks to organizational security.
Identify emails that were send from an address external to your company and where email was send to more then 50 distinct corporate users.
Update corporatedomain.com to your corporate domain to have it excluded.
Update 50 if you want to adjust the distinct user count.
Update corporatedomain.com to your corporate domain to have it excluded.
Update 50 if you want to adjust the distinct user count.
Count of recipient's email addresses by subject
Count of recipient's email addresses by subject
Count of all Senders and where they were delivered
Count of sender's email addresses by subject
This rule detects when a user is added to an administrative role within Office 365. While adding users to administrative roles is not inherently malicious, it is a sensitive action that warrants validation due to the elevated privileges granted. The rule specifically looks for the 'Add member to role.' event type within Office 365 and requires the role to be present in a predefined watchlist of sensitive roles.
Once a user authenticates to the Azure AD PowerShell application, if they take multiple admin actions indicative of establishing their own persistence with an Entra ID application within a portion of the access token time, alert for additional investigation
Adding users to administrative roles is not malicious, but due to the sensitivity of certain roles, validation should occur when this occurs
The following analytic identifies the creation of new email forwarding rules in an Office 365 environment. It detects events logged under New-InboxRule and Set-InboxRule operations within the o365_management_activity data source, focusing on parameters like ForwardTo, ForwardAsAttachmentTo, and RedirectTo. This activity is significant as unauthorized email forwarding can lead to data exfiltration and unauthorized access to sensitive information. If confirmed malicious, attackers could intercept and redirect emails, potentially compromising confidential communications and leading to data breaches.
This analytic identifies the creation or modification of email inbox rules within an Office 365 environment. It specifically looks for `New-InboxRule` and `Set-InboxRule` operations in the O365 management activity logs where the rule parameters indicate actions such as mail forwarding (`ForwardTo`, `ForwardAsAttachmentTo`, `RedirectTo`), or mail manipulation like deletion (`SoftDeleteMessage`, `DeleteMessage`) or moving to specific folders (`MoveToFolder`, `CopyToFolder`). While legitimate users create inbox rules, adversaries often leverage these techniques to exfiltrate emails, maintain persistence, or hide their activities by deleting or moving security alerts.
The following analytic identifies instances where a service principal in Office 365 Azure Active Directory assigns app roles without standard admin consent. It leverages `o365_management_activity` logs, specifically focusing on the 'Add app role assignment to service principal' operation. This activity is significant for SOCs as it may indicate a bypass of critical administrative controls, potentially leading to unauthorized access or privilege escalation. If confirmed malicious, this could allow an attacker to misuse automated processes to assign sensitive permissions, compromising the security of the environment.
The following analytic identifies the configuration of Azure Active Directory Applications in a manner that allows authentication from external tenants or personal accounts. This configuration can lead to inappropriate or malicious access of any data or capabilities the application is allowed to access. This detection leverages the O365 Universal Audit Log data source.
This analytic identifies the invitation of an external guest user within Azure AD. With Azure AD B2B collaboration, users and administrators can invite external users to collaborate with internal users. External guest account invitations should be monitored by security teams as they could potentially lead to unauthorized access. An example of this attack vector was described at BlackHat 2022 by security researcher Dirk-Jan during his talk `Backdooring and Hijacking Azure AD Accounts by Abusing External Identities`. This detection leverages the Universal Audit Log (UAL)/o365:management:activity sourcetype as a detection data source.
This analytic identifies when changes are made to the external guest policies within Azure AD. Specifically, it looks for the "Update policy." operation targeting "B2BManagementPolicy" in the Office 365 Universal Audit Log. The rule extracts and highlights the specific changes made to allowed/blocked domains for B2B collaboration, indicating whether domains were added or removed. Monitoring these changes is crucial as modifications to external identity policies can impact unauthorized access, as described in the BlackHat 2022 talk "Backdooring and Hijacking Azure AD Accounts by Abusing External Identities."
The analytic detects instances where the O365 advanced audit is disabled for a specific user within the Office 365 tenant. It uses O365 audit logs, focusing on events related to audit license changes in AzureActiveDirectory workloads. This activity is significant because the O365 advanced audit provides critical logging and insights into user and administrator activities. Disabling it can blind security teams to potential malicious actions. If confirmed malicious, attackers could operate within the user's mailbox or account with reduced risk of detection, leading to unauthorized data access, data exfiltration, or account compromise.
This analytic identifies when an O365 email account sends an email and then hard deletes email within a short period (within 1 hour). This behavior may indicate a compromised account where the threat actor is attempting to remove forensic artifacts or evidence of activity. Threat actors often use this technique to prevent defenders and victims from knowing the account has been compromised.
The analytic identifies potential "MFA fatigue" attacks targeting Office 365 users by detecting more than nine Multi-Factor Authentication (MFA) prompts within a 10-minute timeframe. It leverages O365 management activity logs, focusing on Azure Active Directory events with the UserLoginFailed operation, a Success ResultStatus, and an ErrorNumber of 500121. This activity is significant as attackers may exploit MFA fatigue to gain unauthorized access by overwhelming users with repeated MFA requests. If confirmed malicious, this could lead to data breaches, unauthorized data access, or further compromise within the O365 environment. Immediate investigation is crucial.
The following analytic identifies instances where a user in the Office 365 environment grants consent to an application requesting file permissions for OneDrive or SharePoint. It leverages O365 audit logs, focusing on OAuth application consent events. This activity is significant because granting such permissions can allow applications to access, modify, or delete files, posing a risk if the application is malicious or overly permissive. If confirmed malicious, this could lead to data breaches, data loss, or unauthorized data manipulation, necessitating immediate investigation to validate the application's legitimacy and assess potential risks.
The analytic detects when emails are accessed in Office 365 Exchange via Exchange Web Services (EWS) using OAuth-authenticated applications. It leverages the ClientInfoString field to identify EWS interactions and aggregates metrics such as access counts, timing, and client IP addresses, categorized by user, ClientAppId, OperationCount, and AppId. Monitoring OAuth applications accessing emails through EWS is crucial for identifying potential abuse or unauthorized data access. If confirmed malicious, this activity could lead to unauthorized email access, data exfiltration, or further compromise of sensitive information.
This analytic identifies when Office 365 users search for suspicious keywords or have an excessive number of queries to a SharePoint site within a limited timeframe. This behavior may indicate that a malicious actor has gained control of a user account and is conducting discovery or enumeration activities.
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