Detects successful Microsoft 365 portal logins from rare locations. Rare locations are defined as locations that are not commonly associated with the user's account. This behavior may indicate an adversary attempting to access a Microsoft 365 account from an unusual location or behind a VPN.

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Detects successful Microsoft 365 portal logins from impossible travel locations. Impossible travel locations are defined as two different countries within a short time frame. This behavior may indicate an adversary attempting to access a Microsoft 365 account from a compromised account or a malicious actor attempting to access a Microsoft 365 account from a different location.

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In Microsoft Entra ID, permissions to manage resources are assigned using roles. The Global Administrator / Company Administrator is a role that enables users to have access to all administrative features in Entra ID and services that use Entra ID identities like the Microsoft 365 Defender portal, the Microsoft 365 compliance center, Exchange, SharePoint Online, and Skype for Business Online. Adversaries can add users as Global Administrators to maintain access and manage all subscriptions and their settings and resources.

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Identifies an Microsoft 365 illicit consent grant request on-behalf-of a registered Entra ID application. Adversaries may create and register an application in Microsoft Entra ID for the purpose of requesting user consent to access resources in Microsoft 365. This is accomplished by tricking a user into granting consent to the application, typically via a pre-made phishing URL. This establishes an OAuth grant that allows the malicious client applocation to access resources in Microsoft 365 on-behalf-of the user.

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Detects potentially suspicious OAuth authorization activity in Microsoft 365 where the Visual Studio Code first-party application (client_id = aebc6443-996d-45c2-90f0-388ff96faa56) is used to request access to Microsoft Graph resources. While this client ID is legitimately used by Visual Studio Code, threat actors have been observed abusing it in phishing campaigns to make OAuth requests appear trustworthy. These attacks rely on redirect URIs such as VSCode Insiders redirect location, prompting victims to return an OAuth authorization code that can be exchanged for access tokens. This rule may help identify unauthorized use of the VS Code OAuth flow as part of social engineering or credential phishing activity.

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Identifies a Microsoft 365 audit log generated for Threat Intelligence signals by Microsoft Defender for Office 365. Signals generated may relate to services such as Exchange Online, SharePoint Online, OneDrive for Business and others.

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Identifies when an excessive number of files are downloaded from OneDrive using OAuth authentication. Adversaries may conduct phishing campaigns to steal OAuth tokens and impersonate users. These access tokens can then be used to download files from OneDrive.

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Detects a burst of Microsoft 365 user account lockouts within a short 5-minute window. A high number of IdsLocked login errors across multiple user accounts may indicate brute-force attempts for the same users resulting in lockouts.

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Identifies brute-force authentication activity targeting Microsoft 365 user accounts using failed sign-in patterns that match password spraying, credential stuffing, or password guessing behavior. Adversaries may attempt brute-force authentication with credentials obtained from previous breaches, leaks, marketplaces or guessable passwords.

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Identifies sign-ins on behalf of a principal user to the Microsoft Graph API from multiple IPs using the Microsoft Authentication Broker or Visual Studio Code application. This behavior may indicate an adversary using a phished OAuth refresh token.

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Identifies an excessive number of Microsoft 365 mailbox items accessed by a user either via aggregated counts or throttling. Microsoft audits mailbox access via the MailItemsAccessed event, which is triggered when a user accesses mailbox items. If more than 1000 mailbox items are accessed within a 24-hour period, it is then throttled. Excessive mailbox access may indicate an adversary attempting to exfiltrate sensitive information or perform reconnaissance on a target's mailbox. This rule detects both the throttled and unthrottled events with a high threshold.

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Identifies suspicious Microsoft 365 mail access by ClientAppId. This rule detects when a user accesses their mailbox using a client application that is not typically used by the user, which may indicate potential compromise or unauthorized access attempts. Adversaries may use custom or third-party applications to access mailboxes, bypassing standard security controls. First-party Microsoft applications are also abused after OAuth tokens are compromised, allowing adversaries to access mailboxes without raising suspicion.

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Identifies when a user creates a new inbox rule in Microsoft 365 that deletes or moves emails containing suspicious keywords. Adversaries who have compromised accounts often create inbox rules to hide alerts, security notifications, or other sensitive messages by automatically deleting them or moving them to obscure folders. Common destinations include Deleted Items, Junk Email, RSS Feeds, and RSS Subscriptions. This is a New Terms rule that triggers only when the user principal name and associated source IP address have not been observed performing this activity in the past 14 days.

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Identifies the assignment of rights to access content from another mailbox. An adversary may use the compromised account to send messages to other accounts in the network of the target organization while creating inbox rules, so messages can evade spam/phishing detection mechanisms.

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Identifies attempts to register a new device in Microsoft Entra ID after OAuth authentication with authorization code grant. Adversaries may use OAuth phishing techniques to obtain an OAuth authorization code, which can then be exchanged for access and refresh tokens. This rule detects a sequence of events where a user principal authenticates via OAuth, followed by a device registration event, indicating potential misuse of the OAuth flow to establish persistence or access resources.

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Identifies the deletion of an anti-phishing policy in Microsoft 365. By default, Microsoft 365 includes built-in features that help protect users from phishing attacks. Anti-phishing polices increase this protection by refining settings to better detect and prevent attacks.

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Identifies the modification of an anti-phishing rule in Microsoft 365. By default, Microsoft 365 includes built-in features that help protect users from phishing attacks. Anti-phishing rules increase this protection by refining settings to better detect and prevent attacks.

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Identifies when a DomainKeys Identified Mail (DKIM) signing configuration is disabled in Microsoft 365. With DKIM in Microsoft 365, messages that are sent from Exchange Online will be cryptographically signed. This will allow the receiving email system to validate that the messages were generated by a server that the organization authorized and were not spoofed.

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Identifies when a Data Loss Prevention (DLP) policy is removed in Microsoft 365. An adversary may remove a DLP policy to evade existing DLP monitoring.

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Identifies when a malware filter policy has been deleted in Microsoft 365. A malware filter policy is used to alert administrators that an internal user sent a message that contained malware. This may indicate an account or machine compromise that would need to be investigated. Deletion of a malware filter policy may be done to evade detection.

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Identifies when a malware filter rule has been deleted or disabled in Microsoft 365. An adversary or insider threat may want to modify a malware filter rule to evade detection.

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Identifies when a new role is assigned to a management group in Microsoft 365. An adversary may attempt to add a role in order to maintain persistence in an environment.

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Identifies when a safe attachment rule is disabled in Microsoft 365. Safe attachment rules can extend malware protections to include routing all messages and attachments without a known malware signature to a special hypervisor environment. An adversary or insider threat may disable a safe attachment rule to exfiltrate data or evade defenses.

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Identifies when a Safe Link policy is disabled in Microsoft 365. Safe Link policies for Office applications extend phishing protection to documents that contain hyperlinks, even after they have been delivered to a user.

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Identifies a transport rule creation in Microsoft 365. As a best practice, Exchange Online mail transport rules should not be set to forward email to domains outside of your organization. An adversary may create transport rules to exfiltrate data.

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Identifies when a transport rule has been disabled or deleted in Microsoft 365. Mail flow rules (also known as transport rules) are used to identify and take action on messages that flow through your organization. An adversary or insider threat may modify a transport rule to exfiltrate data or evade defenses.

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Identifies when a new Inbox forwarding rule is created in Microsoft 365. Inbox rules process messages in the Inbox based on conditions and take actions. In this case, the rules will forward the emails to a defined address. Attackers can abuse Inbox Rules to intercept and exfiltrate email data without making organization-wide configuration changes or having the corresponding privileges.

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Identifies when Microsoft Cloud App Security reports that a user has uploaded files to the cloud that might be infected with ransomware.

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Identifies when custom applications are allowed in Microsoft Teams. If an organization requires applications other than those available in the Teams app store, custom applications can be developed as packages and uploaded. An adversary may abuse this behavior to establish persistence in an environment.

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Identifies when external access is enabled in Microsoft Teams. External access lets Teams and Skype for Business users communicate with other users that are outside their organization. An adversary may enable external access or add an allowed domain to exfiltrate data or maintain persistence in an environment.

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Identifies when guest access is enabled in Microsoft Teams. Guest access in Teams allows people outside the organization to access teams and channels. An adversary may enable guest access to maintain persistence in an environment.

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Identifies that a user has deleted an unusually large volume of files as reported by Microsoft Cloud App Security.

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Identifies when a user has been restricted from sending email due to exceeding sending limits of the service policies per the Security Compliance Center.

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Identifies a new or modified federation domain, which can be used to create a trust between O365 and an external identity provider.

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Detects the occurrence of emails reported as Phishing or Malware by Users. Security Awareness training is essential to stay ahead of scammers and threat actors, as security products can be bypassed, and the user can still receive a malicious message. Educating users to report suspicious messages can help identify gaps in security controls and prevent malware infections and Business Email Compromise attacks.

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Identifies accounts with a high number of single sign-on (SSO) logon errors. Excessive logon errors may indicate an attempt to brute force a password or SSO token.

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Detects the occurrence of mailbox audit bypass associations. The mailbox audit is responsible for logging specified mailbox events (like accessing a folder or a message or permanently deleting a message). However, actions taken by some authorized accounts, such as accounts used by third-party tools or accounts used for lawful monitoring, can create a large number of mailbox audit log entries and may not be of interest to your organization. Because of this, administrators can create bypass associations, allowing certain accounts to perform their tasks without being logged. Attackers can abuse this allowlist mechanism to conceal actions taken, as the mailbox audit will log no activity done by the account.

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Identifies the occurence of files uploaded to OneDrive being detected as Malware by the file scanning engine. Attackers can use File Sharing and Organization Repositories to spread laterally within the company and amplify their access. Users can inadvertently share these files without knowing their maliciousness, giving adversaries opportunity to gain initial access to other endpoints in the environment.

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Identifies the occurence of files uploaded to SharePoint being detected as Malware by the file scanning engine. Attackers can use File Sharing and Organization Repositories to spread laterally within the company and amplify their access. Users can inadvertently share these files without knowing their maliciousness, giving adversaries opportunities to gain initial access to other endpoints in the environment.

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