What is logic bomb? Definition, Examples and Ways to Prevent It

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Imagine a regular day in the digital world turning chaotic – essential data vanishing, systems crashing, and operations coming to a sudden stop. That’s the havoc a logic bomb brings when it detonates in a computer system. These silent troublemakers, hidden in code, set off a chain of destructive events upon activation.

Grasping the true nature of a logic bomb is crucial to realising the urgency of defending against this significant threat. Within this article, we aim to demystify the complexity of logic bombs, delve into real-world examples that have had a profound impact on organisations, and provide you with the essential knowledge to shield against these digital time bombs.

What is a logic bomb?

A logic bomb is a type of slag code or software that is intentionally inserted into a computer system to execute a specific action when certain conditions are met. It is designed to remain dormant or undetected until triggered by a specific event or a predefined timeframe. Once activated, a logic bomb can cause various harmful effects, such as damaging or deleting data, disrupting system operations, or launching additional malicious activities.

While viruses and worms actively spread across systems, a logic bomb lies in wait, embedded within legitimate software or systems. Its activation is contingent upon a particular circumstance, distinguishing it from the more aggressive nature of traditional malware.

How Logic Bombs Work? Creation and Activation

Logic bombs are typically created by programmers who have authorised access to a system or software. These individuals intentionally insert malicious script or code into a program or system during its development or maintenance phase. The code is often disguised or obfuscated to evade detection. Certain types of malware, such as viruses, may contain logic bombs that can inflict damage on a system or network.

The activation of a logic bomb is triggered by specific events or conditions. These events can include a particular date or time, a specific user action, the presence or absence of certain files or data, or even a combination of factors. Once the trigger criteria are met, the logic bomb executes its payload, which can involve deleting files, modifying data, or launching other harmful activities.

Can Logic bomb self-replicate?

No, a logic bomb typically does not self-replicate. Unlike viruses or worms, which are capable of spreading independently, a logic bomb is a standalone piece of code embedded within a system with a specific trigger condition. It relies on external factors, such as user actions or certain dates, to activate and carry out its intended malicious actions.

Who leaves logic bombs in a system?

Logic bombs are commonly used for various purposes by individuals who have access to a targeted system and possess the necessary technical knowledge to insert malicious code without detection. These individuals can include former employees, competitors or hackers, external contractors or service providers with system access, and ideologically motivated hacktivists expressing their beliefs.

Also Read: How Can You Avoid Downloading Malicious Codes?

The common uses of logic bombs are:

  1. Revenge: Disgruntled employees or individuals may create logic bombs as a means of retaliation against their employers or specific individuals. They may set the logic bomb to activate after their departure or at a specific time to cause damage or disruption.
  2. Sabotage: Logic bombs can be used for sabotage purposes, such as disrupting critical systems, causing financial loss, or damaging a competitor’s business operations.
  3. Extortion: In some cases, attackers may plant logic bombs in systems and demand a ransom to prevent the activation or to provide instructions for disarming them.
  4. Espionage: Logic bombs can be used as a tool for espionage, allowing unauthorised access to sensitive information or disrupting critical infrastructure.

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What are the Characteristics of a Logic Bomb?

  1. Dormancy: A logic bomb remains dormant within a system until specific conditions, such as a particular date or event trigger, are met. During this dormant phase, it conceals its presence to avoid detection.
  2. Activation Condition: It is programmed to activate based on a predefined condition, such as a specific date, user action, or system event. The activation condition serves as the trigger for the logic bomb to execute its malicious payload.
  3. Malicious Payload: They contain a set of destructive instructions or code, known as the payload, which is executed upon activation. This payload can cause a range of harmful actions, from deleting files to disrupting system functionality.
  4. Concealment Techniques: To evade detection, logic bombs often employ concealment techniques, blending in with legitimate code or files. This helps the malicious script or code avoid triggering security measures and allows it to remain undetected until the activation criteria are met.

Is a Logic Bomb and a Time Bomb the Same?

While both a logic bomb and a time bomb are types of malicious software designed to execute specific actions under predetermined conditions, they are not precisely the same.

Logic Bomb: A logic bomb is a piece of code that remains dormant until certain conditions or triggers are met. These triggers can include specific dates and times, events, or user actions. Once a logic bomb activates, it executes a malicious payload, which can involve damaging or disrupting a system.

Time Bomb: A time bomb, on the other hand, is a specific type of logic bomb that is triggered based on a predefined time or date. It is essentially a delayed-action logic bomb, as it remains inactive until the specified time elapses. Time bombs are often used for actions like data deletion, system disruption, or other malicious activities that occur at a specific moment.

7 Real-life Examples of Logic Bomb Attack


In February 2000, Tony Xiaotong Yu faced charges for having installed a logic bomb while employed at Deutsche Morgan Grenfell. Planted in 1996 with a scheduled trigger date of July 20, 2000, the logic bomb was, however, uncovered by fellow programmers before activation. The subsequent process of removing and cleaning up after the installed logic bomb purportedly required several months.


On October 2, 2003, Yung-Hsun Lin, alias Andy Lin, endeavoured to set in motion a logic bomb at Medco Health Solutions Inc.’s headquarters. Initially scheduled to trigger on his birthday in 2004, the logic bomb failed to activate. Lin rectified the error and rescheduled it for his subsequent birthday. However, a Medco computer systems administrator detected and disabled the logic bomb a few months before the revised trigger date.


In June 2006, Roger Duronio, serving as a system administrator at UBS, was charged with orchestrating a plan that involved triggering a logic bomb to inflict harm on the company’s computer network. Roger Duronio, an employee of UBS PaineWebber, successfully deployed a logic bomb against his employer, due to arising from a disagreement over his annual bonus. Consequently, he received a conviction, leading to an 8-year and 1-month prison sentence, along with a restitution order of $3.1 million payable to UBS.


In October 2009, Douglas Duchak, a terminated data analyst at the Colorado Springs Operations Centre of the U.S. Transportation Security Administration, loaded a logic bomb onto a server storing data from the U.S. Marshals. Duchak was sentenced to two years in prison, a $60,587 fine, and placed on probation in January 2011.


On October 29, 2008, a logic bomb was discovered at Fannie Mae, planted by Rajendrasinh Babubhai Makwana, an IT contractor. The bomb was set to activate on January 31, 2009, with the potential to wipe all of Fannie Mae’s 4000 servers. Makwana was convicted on October 4, 2010, and sentenced to 41 months in prison on December 17, 2010.

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On March 20, 2013, South Korea fell victim to a targeted cyberattack featuring a destructive logic bomb virus. This insidious malware not only struck multiple machines but unleashed havoc by simultaneously wiping the hard drives and master boot records of at least three banks and two media companies. Symantec’s analysis further revealed that the logic bomb malware included a specialised component with the capability to erase data on Linux machines, accentuating the severity and sophistication of the attack.


David Tinley, a contract worker for Siemens Corporation, strategically embedded logic bombs in the spreadsheet software he provided for managing equipment. Over a decade into his employment, Tinley executed his plan by causing intentional malfunctions in the software when specific logical conditions were met. Each time the software malfunctioned, Tinley, having hidden the logic bombs, was called upon to “repair” it, demanding additional efforts from Siemens.

This scheme persisted for two years until his absence prompted him to supply the administrative password to Siemens’ IT team during a crash. Consequently, the logic bombs were uncovered, leading to Tinley’s guilty plea on July 19, 2019, for his intentional programming of logic bombs within Siemens’ software.

How to Prevent Logic Bombs Virus?

Safeguarding against the covert menace of logic bombs disguised as computer viruses requires essential preventive measures and robust cybersecurity defences. Here are key measures to fortify your digital security:

1. Regular Code Audits and Monitoring

Conducting routine code audits and system monitoring is essential to fortify your security against cyber attacks. By maintaining vigilance and scrutinising code patterns for any anomalies or suspicious elements, you can take a proactive approach to detect potential threats early on. This preemptive measure ensures that any slag code attempting to infiltrate systems is identified and addressed promptly, bolstering overall cybersecurity resilience.

2. Access Control and Employee Monitoring

Implementing stringent access controls and monitoring employee activities are crucial measures to mitigate the security risk of internal threats, including logic bombs. By limiting access to critical systems and closely observing user behaviour, you can thwart attempts by disgruntled employees or insiders to plant logic bombs. This approach provides an additional layer of security, minimising the likelihood of unauthorised actions that could compromise system integrity.

3. Cybersecurity Training and Awareness Programs

Educating employees about cybersecurity threats, specifically emphasising the nature of logic bombs, is paramount for a robust security posture. Employees should be made aware of potential consequences and be equipped to recognise signs of malicious activities. By fostering a culture of cybersecurity awareness, you can empower your workforce to act as a frontline defence against various cyber threats, enhancing the overall resilience of your organisation’s digital infrastructure.

Also read: How To Measure The Success Of Cyber Awareness Training?

4. Security Software and Updates

Maintaining up-to-date security software and promptly applying system updates is a fundamental practice to patch vulnerabilities that logic bombs might exploit. Regularly updating antivirus programs and firewalls ensures that your organisation’s security mechanisms are equipped to identify and neutralise evolving threats. This approach significantly reduces the risk of logic bombs successfully infiltrating systems by addressing potential entry points and strengthening the overall security posture.


Functioning as a dormant code with the potential for devastating activation, logic bombs underscore the importance of robust security tools and proactive measures. Understanding the nature of logic bombs and their potential consequences and adopting preventive strategies are paramount in safeguarding digital landscapes against these insidious agents. As technology advances, the evolution of logic bombs serves as a reminder that cybersecurity diligence is an ongoing imperative.

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