What is Shimming in Cyber Security? (Complete Guide)

What is Shimming in Cyber Security? (Complete Guide)

Arif Chowdhury
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Last Updated on January 28, 2024 by Arif Chowdhury

Just think: you’re sitting at your desk, going about your day, when suddenly, you receive an email notification. It appears to be from a trusted source, but little do you know that lurking behind it lies a sophisticated cyber-attack technique known as shimming.

Shimming is not your average run-of-the-mill hacking attempt; it’s a clever method used by attackers to exploit vulnerabilities in software and gain unauthorized access to sensitive information.

In the world of cybersecurity, shimming has become increasingly prevalent. Attackers leverage shim databases and manipulate software behavior to their advantage. What makes shimming particularly insidious is its ability to fly under the radar.

By targeting weaknesses in the software stack, these attacks can go undetected for extended periods, leaving organizations vulnerable and exposed.

We’ll explore how attackers use this technique, its impact on security, and what measures individuals and organizations can take to defend against it.

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Understanding Shimming Techniques and Methods

Shimming is a sneaky technique used by cyber attackers to inject malicious code into legitimate processes or functions. They employ various techniques, such as API hooking, DLL injection, and code modification, to carry out shimming attacks.

What is Shimming in Cyber Security?

Let’s delve into these methods in more detail.

API Hooking

API hooking is one of the common techniques used for shimming in cyber security. Attackers intercept system calls made by an application and redirect them to their malicious code instead of the intended destination.

This allows them to manipulate the behavior of the targeted application without being detected.

DLL Injection

DLL (Dynamic Link Library) injection involves injecting malicious code into a running process by manipulating or adding dynamic link libraries. By injecting their DLLs, attackers can execute arbitrary code within a legitimate process, gaining control over its functionalities.

This method enables them to bypass security mechanisms and perform unauthorized actions.

Code Modification

In shimming attacks, attackers may modify the executable code of an application directly. They alter specific instructions or add new ones to achieve their objectives.

By modifying the code flow within an application, they can intercept system calls, modify data flow, or redirect execution paths as desired.

Shims created through these techniques serve as intermediaries between applications and the operating system. They allow attackers to manipulate how applications interact with system resources without raising suspicion.


  • Shimming attacks can be difficult to detect since they exploit legitimate processes.
  • Attackers can gain control over targeted applications without requiring administrative privileges.
  • Shims provide flexibility for attackers to customize their malicious activities within compromised systems.


  • Shimming attacks can cause instability and unexpected behavior in targeted applications.
  • Detection and mitigation of shimming techniques require advanced monitoring tools and security measures.
  • Legitimate software updates or patches may inadvertently disrupt existing shims, exposing potential vulnerabilities.

To properly detect and fight such attacks, cybersecurity professionals need to be aware of the various shimming tactics.

Organizations can enhance system security by identifying and mitigating the symptoms of API hooking, DLL injection, and code modification.

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Differentiating Shimming from Other Cyber Threats

1. Manipulating Software Components

Unlike traditional cyber threats such as malware or ransomware, shimming attacks take a different approach. Instead of creating new malicious software or code, cybercriminals focus on manipulating existing software components.

This means that instead of introducing something entirely new into the system, they exploit vulnerabilities within the software itself.

2. Operating at a Lower Level

Shims operate at a lower level compared to other common cyber threats like viruses or worms. While these traditional threats typically target the operating system or higher-level applications, shimming attacks occur at a deeper level within the software stack.

Differentiating Shimming from Other Cyber Threats

By doing so, attackers can evade detection and bypass security measures that are primarily focused on higher-level threats.

3. Exploiting Software Vulnerabilities

Shimming attacks take advantage of flaws in the software itself, whereas phishing attacks use deceptive tactics to directly target people. These flaws may exist in several different components, including drivers, libraries, and application programming interfaces (APIs).

Cybercriminals can obtain sensitive information without authorization or act on behalf of the user without the user’s knowledge by taking advantage of these flaws.

4. Image Hijacking and Spoofing

One specific example of how shimming attacks work is through image hijacking. Attackers can manipulate an application’s graphical user interface (GUI) by intercepting calls made to graphics libraries and substituting legitimate images with malicious ones.

This allows them to deceive users into interacting with what appears to be a genuine interface while performing actions behind the scenes.

5. Protecting Against Shimming Attacks

To protect against shimming attacks and safeguard sensitive information, it is crucial to implement robust security measures:

  • Regularly update software: Keep all applications and operating systems up-to-date with the latest patches and security fixes.
  • Use reputable security solutions: Install reliable antivirus and anti-malware software that can detect and block potential shimming attacks.
  • Practice safe browsing habits: Be cautious when downloading files or clicking on links from unknown sources, as they may contain malicious code.
  • Enable two-factor authentication (2FA): Implement an additional layer of security by enabling 2FA for important accounts and services.
  • Educate users: Train employees and individuals to be aware of common cyber threats, such as shimming attacks, and how to identify suspicious activities.

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Real-Life Examples of Shimming Attacks

Shimming attacks have been employed by various cybercriminal groups to carry out malicious activities and gain unauthorized access to systems.

Let’s take a look at some real-life examples of how shimming has been used in cyber attacks.

The Carbanak group used shims to steal millions from financial institutions worldwide

The Carbanak group, notorious for their sophisticated cyber attacks targeting financial institutions, utilized shims as part of their modus operandi. By inserting these malicious code snippets into the application layer, they were able to intercept and manipulate data without being detected.

This allowed them to siphon off millions of dollars from banks across the globe.

The GoldenSpy malware employed shims to gain persistence on infected systems in China

In another instance, the GoldenSpy malware made use of shims to establish persistence on infected systems within China. This particular attack targeted software used by foreign companies operating in China.

The malware was able to evade security measures and stay hidden for a long time by using shims, which made it possible for continuous surveillance and data exfiltration.

APT29 (Cozy Bear) utilized shim databases as part of their espionage campaigns.

APT29, also known as Cozy Bear, is a highly sophisticated state-sponsored hacking group that has been involved in espionage campaigns targeting various organizations worldwide. In one notable incident, they employed shim databases as part of their toolkit. These databases contained hooks that allowed them to manipulate system functions and evade detection while carrying out their covert operations.

These real-life examples highlight the versatility and effectiveness of shimming attacks in compromising cybersecurity defenses. Attackers can exploit vulnerabilities in software or hardware components by inserting these malicious code snippets at various layers within an application or operating system.

They can obtain unauthorized access, intercept confidential data, alter data, or continue to have permanent control over compromised systems without drawing attention to themselves by doing this.

Organizations and individuals must remain vigilant and implement robust security measures to protect against shimming attacks. Regular software updates, strong access controls, and the use of reputable security solutions can help mitigate the risk of falling victim to such attacks.

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Protecting Against Shimming: Case Studies and Prevention Strategies

To defend against known shim attacks, it is crucial to implement robust endpoint protection solutions. These security measures work by safeguarding endpoints, such as computers and mobile devices, from potential threats.

Protecting Against Shimming: Case Studies and Prevention Strategies

By using advanced antivirus software and firewalls, these solutions can detect and block malicious code injected through shims.


  • Provides real-time protection against known shim attacks.
  • Helps identify and neutralize suspicious activities on endpoints.


  • May require regular updates to stay effective against emerging threats.
  • Can be resource-intensive for older or less powerful devices.

Regularly Patching Software Vulnerabilities

Regularly patching software vulnerabilities is a vital practice in preventing successful shimming attacks. Software vendors frequently release patches that address security flaws discovered in their applications.

By promptly installing these patches, you can close potential entry points for attackers attempting to exploit shims.


  • Closes security loopholes in applications.
  • Reduces the risk of successful shim attacks.


  • Requires consistent monitoring of software updates.
  • May temporarily disrupt application functionality during the patching process.

Employing Application Whitelisting

Application whitelisting is an effective strategy to prevent unauthorized code execution through shims. This practice involves creating a list of approved applications that are allowed to run on a system while blocking all others.

Businesses can drastically lower the danger of malicious code injection using shims by enacting stringent application control policies.


  • Prevents unauthorized applications from executing on systems.
  • Mitigates the risk of malware infection through shimming techniques.


  • Requires careful management of whitelisted applications.
  • May cause compatibility issues with certain programs or versions.

Limiting User Privileges

Limiting user privileges is another essential step in protecting against shimming attacks. By granting users only the necessary permissions required to perform their tasks, you can minimize the potential impact of malicious code injected through shims.

This practice helps prevent unauthorized access to sensitive data and restricts the ability of attackers to execute malicious actions.


  • Reduces the attack surface by limiting user privileges.
  • Mitigates the risk of unauthorized access to sensitive information.


  • May require additional administrative effort to manage user permissions.
  • Can potentially hinder user productivity if permissions are too restrictive.

Educating Employees on Security Best Practices

Educating employees on security best practices plays a crucial role in preventing successful shimming attacks. By raising awareness about the risks associated with downloading untrusted applications or clicking on suspicious links, employees can become more vigilant in their online activities.

Regular training sessions and reminders about safe computing habits can significantly enhance an organization’s overall security posture.


  • Empower employees to recognize and avoid potential security threats.
  • Creates a culture of cybersecurity awareness within the organization.


  • Requires ongoing training efforts to keep employees up-to-date with evolving threats.
  • Human error or negligence can still pose risks despite education efforts.

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Detecting and Preventing Shimming: Tools and Techniques

To effectively detect and prevent shimming attacks, some several tools and techniques can be utilized.

These methods focus on monitoring system call patterns, using integrity-checking tools, and implementing behavior-based detection mechanisms.

Monitoring System Call Patterns

One way to identify abnormal behavior caused by shims is by monitoring system call patterns. By analyzing the sequence of system calls made by a program or process, it becomes possible to detect any deviations from normal behavior.

This can help in identifying the presence of injected shim code or other malicious activities.


  • Allows for real-time monitoring of system call patterns.
  • Provides insights into abnormal behaviors associated with shimming attacks.


  • Requires continuous monitoring and analysis to effectively identify anomalies.
  • May generate false positives if not properly configured.

Using Integrity-Checking Tools

Tools for integrity verification are essential for identifying changes caused by injected shim code. These programs detect any unauthorized changes by comparing the present state of files or processes with their known good versions. Organizations can swiftly identify the existence of shims or other malicious alterations by routinely conducting integrity checks.


  • Enables proactive detection of unauthorized modifications.
  • Helps maintain the integrity of critical files and processes.


  • Relies on having accurate baseline data for comparison.
  • May require significant computational resources for large-scale deployments.

Behavior-Based Detection Mechanisms

Implementing behavior-based detection mechanisms can be highly effective in flagging suspicious activities associated with shim usage. These mechanisms analyze the behavior of programs or processes during execution, looking for indicators that align with known patterns of shimming attacks.

These systems can provide better defense against shimming threats and adjust to new attack vectors by utilizing machine learning algorithms and heuristics.


  • Offers dynamic detection capabilities based on behavioral analysis.
  • Can identify previously unknown forms of shimming attacks.


  • Requires continuous training and updates to stay effective.
  • May generate false negatives if the attack patterns are not well understood.

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Impact of Shimming on Cyber Security: Consequences and Risks

Unexpected Behaviors and Crashes

Shimming, a technique used in cyber attacks, can have serious consequences for cybersecurity. One major impact is the potential for unexpected behaviors or crashes in shimmed applications. When an application is shimmed, it means that malicious code has been injected into its execution flow.

This can lead to instability and unpredictable actions within the application itself. Users may experience sudden crashes or notice strange behavior while using the compromised application.

Data Breaches and Unauthorized Access

The risks associated with shimming extend beyond mere inconvenience. Shimming attacks have the potential to result in data breaches and unauthorized access to sensitive information.

Once a system has been compromised through shimming, attackers can gain unauthorized access to user credentials, financial data, or other confidential information. This puts individuals and organizations at risk of identity theft, financial loss, or reputational damage.

System Compromise

In addition to data breaches, shimming attacks can also compromise entire systems. Attackers may exploit vulnerabilities introduced by shims to gain control over critical components of a system’s infrastructure.

This could allow them to manipulate or disable security measures such as firewalls or antivirus software, leaving the system vulnerable to further exploitation or malware infections.

Stealthy Nature of Shims

One of the most concerning aspects of shimming attacks is their stealthy nature. Shims are designed to operate covertly within an application’s execution flow without raising suspicion. As a result, they can be challenging to detect and remove from compromised systems.

Traditional antivirus software may not always identify these malicious codes since they often operate at a low level within the operating system itself.

Difficulty in Detection and Removal

Detecting and removing shims requires specialized tools and techniques that go beyond traditional security measures. Cybersecurity professionals need to stay updated on emerging threats related to shimming attacks and employ advanced detection methods to identify compromised systems.

Removing shims effectively requires a comprehensive understanding of the affected application’s architecture and dependencies.

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Key Takeaways

In today’s digital landscape, where cyber threats lurk at every corner, it is crucial to understand the significance of shimming in cyber security. Shimming techniques and methods have become increasingly prevalent among hackers and pose a significant risk to individuals and organizations alike. By exploiting vulnerabilities in software or hardware, shimming attacks can bypass traditional security measures undetected.

Differentiating shimming from other cyber threats is essential for effectively combating this menace. While phishing and malware attacks are more widely known, shimming operates with subtlety, making it harder to detect. It stealthily inserts malicious code into legitimate processes or applications, thereby compromising the integrity of systems without raising any red flags.

Real-life examples of shimming attacks further emphasize its impact on cybersecurity. From compromised ATMs to data breaches in point-of-sale systems, the consequences can be severe. These incidents highlight the urgent need for robust prevention strategies and detection tools that can safeguard against such attacks.

To protect yourself or your organization from potential shimming threats, it is crucial to stay informed about the latest prevention strategies and employ reliable detection tools. Regularly update your software and operating systems to patch any vulnerabilities that could be exploited by shimmers. Implement multi-factor authentication whenever possible, as this adds an extra layer of protection against unauthorized access.

Understanding the significance of shimming in cyber security is vital for safeguarding against this stealthy threat. By staying informed about prevention strategies and utilizing effective detection tools, you can enhance your defenses against these insidious attacks.

Frequently Asked Questions (FAQs)

What are some signs that my system may have been compromised by a shim?

If you notice unusual behavior like unexpected pop-ups or changes in system settings without your authorization, these could be signs of a potential shim attack. If your antivirus software detects suspicious files or activities but fails to remove them, it could indicate a shim compromise.

Can shimming attacks be prevented entirely?

While it is challenging to eliminate the risk of shimming attacks, implementing strong security practices can significantly reduce the likelihood of falling victim. Regularly updating software and operating systems, using reputable security solutions, and educating yourself about potential threats are essential steps toward prevention.

Are there any specific industries that are more vulnerable to shimming attacks?

Shimming attacks can target any industry or individual using vulnerable software or hardware. However, industries handling financial transactions (such as banking or retail) are often prime targets due to the potential for monetary gain.

How can I detect if my system has been compromised by a shim?

Regularly monitoring your system for unusual activities or unexpected changes is crucial. Employing reliable antivirus software and intrusion detection systems can help identify potential shim compromises. Staying informed about the latest threat intelligence and security updates can enhance your ability to detect such attacks.

What should I do if I suspect a shim attack on my system?

If you suspect a shim attack on your system, take immediate action. Disconnect from the internet to prevent further compromise and run a full scan with updated antivirus software. If you lack technical expertise, seek assistance from cybersecurity professionals who can investigate and remediate the issue effectively.