Thread Local Storage

Adversaries may inject malicious code into processes via thread local storage (TLS) callbacks in order to evade process-based defenses as well as possibly elevate privileges. TLS callback injection is a method of executing arbitrary code in the address space of a separate live process. TLS callback injection involves manipulating pointers inside a portable executable (PE) to redirect a process to malicious code before reaching the code's legitimate entry point. TLS callbacks are normally used by the OS to setup and/or cleanup data used by threads. Manipulating TLS callbacks may be performed by allocating and writing to specific offsets within a process’ memory space using other [Process Injection](https://attack.mitre.org/techniques/T1055) techniques such as [Process Hollowing](https://attack.mitre.org/techniques/T1055/012).(Citation: FireEye TLS Nov 2017) Running code in the context of another process may allow access to the process's memory, system/network resources, and possibly elevated privileges. Execution via TLS callback injection may also evade detection from security products since the execution is masked under a legitimate process.

Linked Issues

Issuelinks
Linktype	Issue
is related to	Techniques
is blocked by	Detection Strategy for TLS Callback Injection via PE Memory Modification and Hollowing
is blocked by	Behavior Prevention on Endpoint
is blocked by	Continuous Monitoring
is blocked by	Malicious Code Protection (Anti-Malware)
is blocked by	Mobile Code
is blocked by	Least Privilege
is blocked by	Boundary Protection
is blocked by	Software & Firmware Patching

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