DLL hijacking
DLL Hijacking
DLL hijacking, also referred to as "binary planting," is a cyber attack technique that takes advantage of the Windows search and loading process for dynamic-link libraries (DLLs). In this attack, a malicious actor strategically places a fake DLL file, often disguised as a legitimate file, in a location where the operating system will prioritize it over the genuine DLL. Consequently, when the system attempts to load the DLL, it inadvertently executes the unauthorized code implanted by the attacker.
How DLL Hijacking Works
The process of DLL hijacking typically involves the following steps:
Identifying Vulnerable Applications: Attackers conduct reconnaissance to identify applications that do not specify the full path to the DLLs they require. These applications depend on the system's search order to locate and load the necessary DLLs.
Placing Malicious DLLs: Once a vulnerable application is identified, the attacker places a malicious DLL with the same name as the legitimate DLL in a location favored by the system's search order. Common locations include the application's directory, Windows system directories, or the current working directory.
Triggering Execution: When the vulnerable application is launched, the operating system initiates the search and loading of DLLs following the search order. Unfortunately, due to the malicious DLL's placement, the system inadvertently loads and executes the attacker's code instead of the intended legitimate DLL.
This method of attack can be leveraged by threat actors to execute arbitrary code within the context of the targeted application, bypassing security measures and potentially compromising the integrity and confidentiality of the system.
Prevention Tips
To mitigate the risk of DLL hijacking attacks, consider the following prevention measures:
Full Path Specification: Developers should explicitly specify the full path for the DLL to be loaded rather than relying on the system's search order. By providing the complete path, developers ensure that the intended DLL is loaded, eliminating the possibility of an attacker redirecting the system to a malicious DLL.
Code Signing: Implementing code-signing practices enhances the integrity and authenticity of DLLs loaded by applications. Code signing involves digitally signing DLLs with a trusted certificate authority (CA), allowing the system to verify the integrity and origin of the DLL before loading it. This practice helps prevent the execution of tampered or malicious DLLs.
User Permissions: Limiting user permissions plays a crucial role in preventing unauthorized users from manipulating DLLs or placing them in susceptible locations that can be hijacked. By enforcing proper access controls, organizations can reduce the risk of DLL hijacking attacks.
Disable Auto-Loading: Disabling the automatic DLL search and loading feature can be an effective defense against DLL hijacking. This can be achieved by removing the current working directory from the system's search path. By doing so, the system will only load DLLs explicitly specified with a full path, minimizing the risk of unintended DLL execution.
It is important for organizations to prioritize securing their applications and systems against DLL hijacking and implement these preventive measures to mitigate potential risks.
Related Terms
DLL Injection: DLL injection is the act of forcing a process to load a dynamic-link library (DLL). This technique can be employed for legitimate purposes, such as extending functionality, but it can also serve as a method for cyber attacks.
Rootkit: A rootkit is a type of malicious software designed to gain unauthorized access and control over a computer system while evading detection. Rootkits operate with elevated privileges, allowing them to conceal their presence and provide a covert platform for attackers to compromise systems or collect sensitive information.
Sources:
- Microsoft Security Advisory 2269637: Insecure Library Loading Could Allow Remote Code Execution
- OWASP: DLL Hijacking