What is Shimming in Cyber Security?

When it comes to cyber security, it is crucial to stay updated on the latest threats and vulnerabilities that can compromise the integrity of your systems. One such threat that has gained attention in recent years is shimming. In this article, we will explore what shimming is, how it works, and what you can do to protect yourself against it.

Understanding Shimming

Shimming is a technique used by cyber criminals to intercept and modify data exchanged between software components. It involves inserting a malicious code layer between the application and the operating system, allowing the attacker to intercept and manipulate the data without the user’s knowledge.

Shimming attacks typically target the Windows operating system, taking advantage of its dynamic-link library (DLL) infrastructure. DLLs are files that contain code and data that multiple programs can use simultaneously. By inserting a shim into the DLL loading process, attackers can gain unauthorized access to sensitive information or execute malicious commands.

How Shimming Works

Shimming attacks exploit the way Windows loads DLLs when an application is launched. When an application needs to access a specific DLL, it searches for the DLL in a predefined order. Attackers take advantage of this process by creating a malicious shim DLL with the same name as a legitimate DLL, tricking the system into loading the malicious code instead.

Once the malicious shim is loaded, it hooks into the application’s code and intercepts the data being exchanged between the application and the operating system. This allows the attacker to manipulate the data, steal sensitive information, or execute arbitrary commands.

Protecting Against Shimming Attacks

While shimming attacks can be sophisticated and difficult to detect, there are several measures you can take to protect yourself and your systems:

  1. Keep your software up to date: Regularly update your operating system and applications to ensure you have the latest security patches and fixes. This can help protect against known vulnerabilities that attackers may exploit.
  2. Implement strong access controls: Limit user privileges and restrict access to critical systems and sensitive data. By implementing strong access controls, you can reduce the risk of unauthorized access and minimize the impact of a shimming attack.
  3. Use reputable security software: Install and regularly update antivirus and anti-malware software to detect and remove any malicious code, including shims. Make sure your security software is from a trusted source and has a good reputation in the industry.
  4. Be cautious of suspicious emails and downloads: Avoid clicking on suspicious links or downloading files from untrusted sources. Cyber criminals often use phishing emails and malicious downloads to distribute shimming malware.
  5. Monitor system logs: Regularly review system logs for any unusual or suspicious activity. Monitoring system logs can help you detect signs of a shimming attack and take appropriate action.

By following these best practices and staying vigilant, you can significantly reduce the risk of falling victim to a shimming attack. It is important to stay informed about the latest cyber security threats and take proactive steps to protect your systems and data.


Shimming is a technique used by cyber criminals to intercept and modify data exchanged between software components. By understanding how shimming works and implementing security measures, you can protect yourself and your systems against this type of attack. Regularly updating your software, implementing strong access controls, using reputable security software, being cautious of suspicious emails and downloads, and monitoring system logs are all important steps in mitigating the risk of shimming attacks. Stay informed and proactive to stay one step ahead of cyber criminals.

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