Detections
Explore public detection logic contributed by the community across SIEM and rule languages.
837 detections
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Detects post-compromise inbox rule creation that moves security/phishing alerts to a folder and marks them as read. This behavior is often associated with adversaries attempting to hide their activities or prevent detection.
Detects inbound emails that are fully authenticated (SPF, DKIM, DMARC pass) and contain keywords related to 'code of conduct', 'employee handbook', 'policy acknowledgement', or 'compliance update' in the subject line, originating from a sender domain that has not been observed by the recipient organization within the last 24 hours. This rule aims to identify potential phishing attempts leveraging social engineering themes from newly registered or previously unseen domains.
Detects email bombing attacks via high-volume inbound email delivery
Identifies emails where the sender claims to be internal, but the X-MS-Exchange-Organization-AuthAs header is not set to 'Internal', indicating a potential Ghost-Sender exploit. This rule focuses on delivered emails to reduce noise and filters out expected external mail gateways and trusted automated senders.
Identifies inbound emails claiming to be from an internal domain where the sender IP does not match the expected authorized third-party MX record or spam filter IP addresses. This rule focuses on emails successfully delivered to the user, where the sender domain claims to be one of the organization's internal domains, and the sending IP is not among the expected external MX or spam filter IP addresses.
Detects creation of inbox rules to hide attacker communications from victim
This rule detects potential direct send email spoofing attempts where an email fails SPF, DKIM, and DMARC authentication checks, but passes Composite Authentication (CompAuth). Additionally, it looks for emails where the sender's local part (username before the @) matches the recipient's local part, suggesting an attempt to impersonate an internal user. The rule also filters out emails that were blocked and those sent via internal connectors, focusing on external spoofing attempts. It further excludes emails originating from specific countries (New Zealand, Australia) which can be customized.
This detection identifies when an email that contains a URL associated with a known Remote Monitoring and Management (RMM) tool was sent and subsequently clicked by the intended recipient or the original sender. The domain is not part of the organization's approved RMM solutions, indicating a potential use of Living-off-the-Land RMM (LOLRMM) techniques often employed in initial access or persistence stages by threat actors.
This activity may reflect attempted remote access, lateral movement, or data collection through unauthorized RMM deployment.
This activity may reflect attempted remote access, lateral movement, or data collection through unauthorized RMM deployment.
Detects inbound external emails where the sender's display name exactly matches the recipient's display name. This is a common social engineering tactic used to create a false sense of familiarity, making the recipient more likely to trust the email and its contents. The rule specifically excludes legitimate self-sent emails where the sender's and recipient's email addresses also match.
Detects inbound email that fails SPF authentication indicating email spoofing
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 a high volume of inbound emails to port 25 (SMTP), indicating a potential email bombing attack. It triggers an alert if more than 100 emails are received from a single source IP address within a 60-second window.
This rule detects emails sent to the internal network (SMTP port 25) that attempt to impersonate an internal IT department. It specifically looks for the 'From:' header, the phrase 'IT Department' (case-insensitive), and the word 'password' (case-insensitive) within the email content. This combination suggests a social engineering attempt, likely phishing, to trick recipients into revealing credentials.
This rule detects when a single user removes permissions from 5 or more mailboxes within a one-hour window in an Exchange environment. This activity could indicate an attempt to cover tracks or disrupt access to mailboxes by an attacker.
This rule detects emails containing macro-enabled documents (.docm, .xlsm, .pptm). It specifically looks for instances where a sender sends two or more such emails within an hour, which could indicate a targeted phishing attempt using malicious macros.
Detects suspicious emails with attachments originating from external senders, characterized by urgent or action-oriented subject lines, and sent in bulk (5 or more emails within an hour). This pattern is indicative of phishing attempts.
This rule detects emails containing macro-enabled documents (.docm, .xlsm, .pptm). It specifically looks for instances where a sender sends two or more such emails within an hour, which could indicate a targeted phishing attempt using malicious macros.
Detects suspicious emails with attachments originating from external senders, characterized by urgent or action-oriented subject lines, and sent in bulk (5 or more emails within an hour). This pattern is indicative of phishing attempts.
This rule detects SMTP traffic where an email is failing SPF (Sender Policy Framework) authentication. Specifically, it looks for the 'Received-SPF: fail' header in emails sent to port 25 ($HOME_NET). This indicates that the sending server is not authorized to send email on behalf of the domain specified in the email's 'MAIL FROM' address, which is a strong indicator of a phishing attempt or spoofed email.
This rule detects emails containing archive file attachments (zip, rar, 7z). It summarizes the count of such archives per sender, recipient, and file name over a daily period. The rule specifically looks for instances where at least one archive is present in an email.
This rule detects potential thread hijacking phishing attempts where an email with a subject starting with 'RE:' or 'FW:' (indicating a reply or forward) contains an attachment with a suspicious file extension (.js, .hta, or .lnk). The rule specifically looks for these emails originating from domains outside of a predefined list of trusted domains and flags instances where more than one such suspicious reply/forward is sent from the same sender with the same subject and filename within a day, suggesting a coordinated attack.
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