Web Session Cookie
Where this stands
No Sigma rule can address this — the telemetry MITRE names has no Sigma logsource behind it.
None of MITRE's analytics for this technique name a log source that maps to a Sigma logsource — they describe abstract data ("Process::None"), API-hook telemetry, or prose channels with no reliable field names behind them.
What the technique is
Adversaries can use stolen session cookies to authenticate to web applications and services. This technique bypasses some multi-factor authentication protocols since the session is already authenticated. Authentication cookies are commonly used in web applications, including cloud-based services, after a user has authenticated to the service so credentials are not passed and re-authentication does not need to occur as frequently. Cookies are often valid for an extended period of time, even if the web application is not actively used. After the cookie is obtained through Steal Web Session Cookie or Web Cookies, the adversary may then import the cookie into a browser they control and is then able to use the site or application as the user for as long as the session cookie is active. Once logged into the site, an adversary can access sensitive information, read email, or perform actions that the victim account has permissions to perform. There have been examples of malware targeting session cookies to bypass multi-factor authentication systems.
Read it on attack.mitre.orgWhat MITRE says you would watch
- AN0201
Anomalous access to cloud web applications using session tokens without corresponding MFA/credential validation, often from unusual locations or device fingerprints.
- AN0202
Session cookie reuse on unmanaged browsers, devices, or client types deviating from user baseline (e.g., switching from Chrome to curl).
- AN0203
Web session tokens reused in native Office apps (e.g., Outlook, Teams) without associated token refresh or login behavior on the endpoint.
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