Detections
Explore public detection logic contributed by the community across SIEM and rule languages.
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This rule detects suspicious activity where a user successfully performs a multi-factor authentication (MFA) device login to Microsoft Office 365 via a browser, and within a 15-minute window, the same user either creates a new inbox rule or adds a new device. This combination of events could indicate an adversary gaining initial access and then setting up persistence (e.g., forwarding emails) or further device enrollment.
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 potential mass email collection activity over IMAP (port 143). It triggers an alert if a client makes 20 or more 'FETCH BODY[]' requests within a 60-second window to an IMAP server. This behavior is indicative of an attacker or malicious script attempting to download a large number of email bodies, potentially for data exfiltration or analysis.
This rule detects a high volume of IMAP/SSL connections to port 993 from a single source IP address within a short timeframe, which could indicate an attempt to collect emails in bulk, potentially associated with MITRE ATT&CK technique T1114 (Email Collection). The threshold is set to 30 connections within 60 seconds from the same source.
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.
Detects a temporal pattern characteristic of CVE-2026-42897 XSS exploitation: an OWA user reads a message (via Bind, OpenMessage, or similar EWS/OWA endpoints), and within 60 seconds, the same session issues a POST request to create or modify an inbox rule. This rapid succession from the same session cookie indicates programmatic action (XSS-driven JavaScript) rather than human-driven workflow. The rule correlates events by client IP and username within a 60-second window.
Detects unauthorized processes reading or accessing the 'PhoneExperiences' SQLite databases. This behavior may indicate an attempt to steal synchronized SMS messages or One-Time Passwords (OTPs) via the Microsoft Phone Link application, bypassing MFA without needing mobile malware.
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.
Hacktool Ruler
Sigma
This events that are generated when using the hacktool Ruler by Sensepost
This rule detects emails that contain keywords related to 'civil id' in English or Arabic and subsequently extract potential Civil ID numbers from the email body. It then validates the extracted numbers based on birth month and day, and categorizes the risk level based on sender's domain and attachment count. This could indicate data exfiltration or sensitive information exposure.
This rule detects phishing attempts related to a Booking.com campaign. It identifies suspicious URLs containing 'op_token' or 'tpo_token' parameters, often combined with paths like 'complaint' or 'reserv', on non-Booking.com domains. It specifically looks for punycode domains (e.g., 'xn--*'), lookalike domains (e.g., '*booklng*', '*mgmnt*', '*portal*'), and specific high-signal punycode domains identified in reports. The rule also includes a pattern for partner kit redirect URLs with 'tpo_token' on 'booklng' subdomains. Additionally, it suggests looking for specific email patterns from Gmail senders with subjects like 'Automatic reply', 'Availability', or 'Reservation' that contain embedded URLs matching 'complaint?op_token='.
In this campaign, the threat actor leveraged specially crafted Microsoft RTF files to exploit CVE-2026-21509 and deliver malicious backdoors in a multi-stage infection chain. Due to significant overlaps in tools, techniques, and procedures (TTPs) between this campaign and those of the Russia-linked advanced persistent threat (APT) group APT28, we attribute this new campaign to APT28 with high confidence. Microsoft released an out-of-band update to address CVE-2026-21509 on January 26, 2026. ThreatLabz observed active in-the-wild exploitation on January 29, 2026.
This query parses the complex JSON parameters of the New-TransportRule and Set-TransportRule commands to find instances where email is being secretly copied externally or security is being lowered.
This rule detects suspicious activity related to mailbox access within Office 365. It has two main parts: 1) Identifies users accessing a high number of unique mailboxes belonging to other users. 2) Identifies users accessing a high number of unique folders within another user's mailbox. Both scenarios can indicate unauthorized access, data exfiltration attempts, or compromised accounts.
This rule detects suspicious activity related to mailbox access within Office 365. It has two main parts: 1) Identifies users accessing a high number of distinct mailboxes belonging to other users. 2) Identifies users accessing a high number of distinct folders within another user's mailbox. Both parts are designed to flag potential unauthorized access, data exfiltration, or reconnaissance activities within an Exchange Online environment.
To detect sensitive or confidential information sent by email from our users, I discovered that DefenderXDR is registering events when some user or services is reading files tagged or marked as sensitive. Basically, it has a "SensitiveFileRead" ActionType in the DeviceFileEvents table which indicates that a process on the monitored device has accessed a file classified as sensitive. This could include files with personally identifiable information (PII), intellectual property, or other data deemed sensitive based on the organization’s data protection policies or Microsoft’s predefined rules. This event type is essential for tracking access to sensitive data, helping to identify potential data leakage or unauthorized access attempts.
This detection looks for cases where a user has downloaded an attachment from 3 or more separate emails over a 24 hour period. This activity could indicate an insider risk collecting documents prior to data exfiltration.
The limit for this can be altered based on baseline company behaviour.
The limit for this can be altered based on baseline company behaviour.
This rule detects suspicious access to files with sensitive extensions commonly associated with email archives, database files, memory dumps, and remote desktop connection files. Monitoring access to these file types can indicate attempts at data collection, credential dumping, or lateral movement preparation by adversaries.
This YARA rule detects the Veaty backdoor by identifying specific bytecode patterns related to fetching commands, reading mailbox folders, and adding inbox rules. The rule looks for a combination of these patterns within a file that also has a valid MS-DOS executable header (MZ header).
Detects scenarios where an attacker attempt to hide emails in order to perform phishing attacks by replacing, for example, financial information from the original email with another email containing attacker's financial information. This technique may also be used to avoid specific email notification to be received by end users in case, for example, of an ongoing breach.
This rule detects outbound automatic reply emails sent from an organization's users to external recipients. It specifically looks for emails with subjects starting with "Automatic reply:" that have been delivered and are outbound.
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