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Zero Day Exploit

Definition: A Zero Day Exploit is a cyber attack that occurs on the same day a weakness is discovered in software, before the software developers have an opportunity to create a patch to fix the vulnerability. "Zero day" refers to the number of days the software vendor has known about the problem, meaning zero, and thus, had no time to mitigate it.

Zero Day Exploits are significant in the field of cyber security as they exploit vulnerabilities for which no solution is currently available. This renders systems defenceless against such attacks and places a high value on finding security flaws. Cybersecurity professionals and software vendors work diligently to identify potential vulnerabilities to prevent Zero Day Exploits by releasing timely patches and updates. However, if attackers discover a vulnerability first, they can exploit it to cause significant damage, including data breaches, system takeovers, or even widespread Internet disruptions.

These exploits are particularly dangerous because they can bypass traditional security measures. Zero Day attacks can be part of targeted attacks against specific organisations or used as a broader weapon against multiple unpatched systems on the Internet.

Key Characteristics:

  • Unforeseen Attack: Zero Day Exploits take advantage of a vulnerability that is not yet known to the software developer.
  • Swift Action Required: Rapid response is essential to reduce the damage caused by such exploits as there is no pre-existing defence.
  • High Value to Attackers: Vulnerabilities that can be exploited before a patch is available are highly valuable on the black market and among cyber criminals.
  • Difficult to Defend: Traditional security measures may not protect against Zero Day Exploits since they rely on known threat patterns.


  • Real-World Example: The Stuxnet worm, discovered in 2010, used multiple Zero Day Exploits to target industrial control systems without detection.
  • Hypothetical Scenario: An attacker discovers a vulnerability in a web browser that allows them to execute remote code simply by visiting a malicious website. They use this Zero Day Exploit to install malware on users’ computers who visit the site before the browser vendor can release a patch.

Related Terms:

  • Vulnerability: A weakness in software that can be exploited to cause harm or gain unauthorized access.
  • Patch: A software update that fixes vulnerabilities or bugs.
  • Exploit: A piece of software or a sequence of commands that take advantage of a bug or vulnerability to cause unintended or unanticipated behaviour to occur on computer software or hardware.

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Inside you will find a description of the most common web vulnerabilities.

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