Adversaries may take advantage of security vulnerabilities and inherent functionality in browser software to change content, modify user-behaviors, and intercept information as part of various browser session hijacking techniques.
A specific example is when an adversary injects software into a browser that allows them to inherit cookies, HTTP sessions, and SSL client certificates of a user then use the browser as a way to pivot into an authenticated intranet. Executing browser-based behaviors such as pivoting may require specific process permissions, such as
SeDebugPrivilege and/or high-integrity/administrator rights.
Another example involves pivoting browser traffic from the adversary's browser through the user's browser by setting up a proxy which will redirect web traffic. This does not alter the user's traffic in any way, and the proxy connection can be severed as soon as the browser is closed. The adversary assumes the security context of whichever browser process the proxy is injected into. Browsers typically create a new process for each tab that is opened and permissions and certificates are separated accordingly. With these permissions, an adversary could potentially browse to any resource on an intranet, such as Sharepoint or webmail, that is accessible through the browser and which the browser has sufficient permissions. Browser pivoting may also bypass security provided by 2-factor authentication.
IcedID has used web injection attacks to redirect victims to spoofed sites designed to harvest banking and other credentials. IcedID can use a self signed TLS certificate in connection with the spoofed site and simultaneously maintains a live connection with the legitimate site to display the correct URL and certificates in the browser.
|M1018||User Account Management||
Since browser pivoting requires a high integrity process to launch from, restricting user permissions and addressing Privilege Escalation and Bypass User Account Control opportunities can limit the exposure to this technique.
Close all browser sessions regularly and when they are no longer needed.
|ID||Data Source||Data Component|
|DS0028||Logon Session||Logon Session Creation|
This may be a difficult technique to detect because adversary traffic may be masked by normal user traffic. New processes may not be created and no additional software dropped to disk. Authentication logs can be used to audit logins to specific web applications, but determining malicious logins versus benign logins may be difficult if activity matches typical user behavior. Monitor for Process Injection against browser applications.