Detections
Explore public detection logic contributed by the community across SIEM and rule languages.
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Detects anomalous authentication patterns indicative of session token replay attacks. The rule identifies instances where a user successfully performs an MFA-authenticated, interactive sign-in, followed shortly (within 5-60 minutes) by a single-factor sign-in for the same user. The suspicious activity is characterized by a shift to a different IP/ASN, an unmanaged device (non-trusted), and a change in browser or OS identifiers, all while the user's geolocation (city/country) remains consistent. This behavioral pattern is highly consistent with the use of residential proxy infrastructure to replay stolen session tokens, effectively bypassing MFA.
This rule detects potential domain fronting activity used to hide Command and Control (C2) servers. It specifically looks for HTTP traffic where the TLS Server Name Indication (SNI) or HTTP Host header contains known domain fronting providers like cloudfront.net or azureedge.net, combined with a suspicious pattern in the HTTP Host header that includes an 8 or more character alphanumeric string followed by a top-level domain commonly associated with malicious activity (xyz, top, club, icu). This combination suggests an attempt to disguise C2 communications by routing them through legitimate content delivery networks.
This rule detects DNS queries to known dynamic DNS services that are frequently abused by C2 infrastructure. Specifically, it looks for queries ending in '.duckdns.org', '.no-ip.com', '.ddns.net', '.hopto.org', or '.zapto.org'. A threshold of 5 queries within 60 seconds from the same source IP is applied to reduce false positives.
This rule detects HTTP traffic where the 'Host' header contains common Content Delivery Network (CDN) domains (cloudfront.net, azureedge.net, fastly.net, cloudflare.net) and the 'X-Forwarded-Host' header is also present. This pattern can indicate C2 infrastructure attempting to hide behind CDN fronting, a technique used by adversaries to obscure the true origin of their command and control servers.
This rule detects HTTP access to domains or hosts associated with bulletproof hosting infrastructure. It specifically looks for hostnames containing '.ru/', '.cn/', 'frantech', 'serverius', or 'combahton'. A threshold of 5 occurrences within 60 seconds from the same source IP triggers the alert.
'This query over Microsoft Entra ID sign-in activity highlights Microsoft Entra ID apps with
an unusually high ratio of distinct geolocations versus total number of authentications'
an unusually high ratio of distinct geolocations versus total number of authentications'
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