Shimming in cybersecurity is a sophisticated attack technique that involves inserting a small piece of malicious code, known as a shim, between an application and the operating system to intercept and manipulate data flow. This stealthy method allows attackers to bypass security controls, alter digital infrastructure, and potentially gain access to sensitive information such as passwords, credit card details, and personal data.
Shimming in Cyber Security
Shimming in cybersecurity is an attack technique that exploits the trust relationships between software components within a system. Attackers use small pieces of code called “shims” to intercept and manipulate data flow between legitimate applications and the operating system. This technique allows cybercriminals to bypass security controls, alter digital infrastructure, and potentially gain unauthorized access to sensitive information.
The process of a shimming attack typically involves several steps:
- Reconnaissance: Attackers identify vulnerable components or interfaces within the target system.
- Injection: Malicious code is inserted into the system, often through exploitation of existing vulnerabilities or social engineering tactics.
- Interception: The injected shim intercepts data flow between legitimate components, allowing attackers to manipulate or exfiltrate sensitive information.
- Evasion: To avoid detection, attackers may employ various techniques such as obfuscation or encryption to conceal their malicious activities.
DLL Shimming and Exploits
DLL shimming is a specific type of shimming attack that targets Windows Dynamic Link Libraries (DLLs). This technique involves inserting a malicious shim into the DLL system to alter program functions and bypass security measures. Attackers can use DLL shimming to execute malicious code, intercept API calls, or gain unauthorized access to sensitive data. One common exploit is DLL injection, where attackers insert a malicious DLL into a legitimate process, allowing them to run code within the context of a trusted application. This method is particularly dangerous as it can evade detection by antivirus software and exploit the trust placed in legitimate processes.
- DLL shimming can be used to refactor code, making malicious DLLs appear benign to antivirus signatures.
- Attackers may use tools like the Application Compatibility Administrator to create malicious shim databases (SDBs) for targeted applications.
- Once installed, these shims can inject malicious code every time the targeted application launches, providing persistent access to the system.
API Hooking in Cyber Attacks
API hooking is a powerful technique used by both legitimate software and malware to intercept and modify the behavior of Application Programming Interface (API) calls. In cyber attacks, malicious actors leverage API hooking to evade detection, steal sensitive information, and maintain persistence on compromised systems.
- Attackers use API hooking to spy on keystrokes, intercept encrypted communications, and hide malicious processes from security software.
- Common hooking methods include inline hooking (modifying the first few bytes of an API’s code) and Import Address Table (IAT) hooking (altering function pointers).
- Malware like Waterbear has been observed using API hooking to evade specific security products by modifying functions like “ZwOpenProcess” and “GetExtendedTcpTable”.
- Sophisticated malware kits and post-exploitation frameworks, such as Empire and TrickBot, employ API hooking to intercept network traffic and capture credentials.
While API hooking has legitimate uses in software development and debugging, its potential for abuse makes it a significant concern in cybersecurity, requiring advanced detection and mitigation strategies.
Browser Shimming and Phishing Risks
Browser shimming, also known as browser-in-the-middle (BitM) attacks, is a sophisticated technique used by cybercriminals to intercept and manipulate web traffic between a user’s browser and web services. This method often involves luring victims to click on malicious links that redirect them to a compromised browser controlled by the attacker. Once in place, the malicious browser acts as a proxy, allowing attackers to eavesdrop on all communications, including encrypted HTTPS traffic.
These attacks are particularly dangerous when combined with phishing tactics. Attackers may use link shorteners or shimming services to disguise malicious URLs, making it easier to trick users into visiting fake websites designed to steal sensitive information. To protect against browser shimming and associated phishing risks, users should be cautious of unexpected pop-ups, altered browser settings, and suspicious links in emails. Organizations can mitigate these threats by implementing advanced security tools, regularly updating software, and providing comprehensive employee training on recognizing and avoiding phishing attempts.
