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Web Session Cookie

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.[1]

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, the adversary then imports the cookie into a browser they control and is 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.[2]

ID: T1506
Tactic: Defense Evasion, Lateral Movement
Platform: Office 365, SaaS
Data Sources: Authentication logs, Office 365 account logs
Defense Bypassed: Logon Credentials, Multi-Factor Authentication
Contributors: Johann Rehberger
Version: 1.0
Created: 08 October 2019
Last Modified: 17 October 2019


Mitigation Description
Software Configuration

Configure browsers or tasks to regularly delete persistent cookies.


Monitor for anomalous access of websites and cloud-based applications by the same user in different locations or by different systems that do not match expected configurations.