Zero-day exploits: Everything you need to know in 2025

A zero-day exploit is one of the most dangerous weapons in a cybercriminal’s arsenal. Unlike typical cyber attacks that target known vulnerabilities, zero-day exploits strike at previously undiscovered weaknesses in software or hardware – giving defenders zero days to prepare. 

In this comprehensive guide, we’ll explore what makes these threats so dangerous and how organizations can protect themselves in 2025’s evolving threat landscape.

What is a zero-day exploit?

A zero-day exploit is a cybersecurity vulnerability that is unknown to the software vendor or security community, leaving it open to exploitation by cybercriminals before a patch can be developed, meaning it has not been patched yet. 

The term “zero-day” refers to the fact that developers have zero days to fix the issue before it can be exploited in the wild. These vulnerabilities often provide hackers with unauthorized access to systems, enabling data theft, malware deployment, and other malicious activities.

Hackers can take advantage of these vulnerabilities to infiltrate systems, often launching attacks before the software maker is even aware of the issue. Since no fix exists, these exploits can cause significant damage, making early detection and response crucial for security teams. Think of it like a hidden door in a building that no one knows about — once a hacker finds it, they can slip right in unnoticed, with no one around to stop them.

How zero-day attacks work

1. Attackers discover a vulnerability in a system or application.
2. They develop exploit code to take advantage of the flaw.
3. The exploit is used to launch attacks, often through social engineering tactics.
4. Victims are compromised before developers become aware of the issue.

Common targets

Zero-day exploits can affect a wide range of systems, including:

• Operating systems
• Web browsers
• Office applications
• Hardware and firmware
• Internet of Things (IoT) devices

Why are zero-day exploits dangerous?

Zero-day exploits are dangerous because they target vulnerabilities that are unknown to software vendors and security teams, meaning there are no patches or defenses readily available. This allows attackers to exploit these flaws before they are discovered and fixed, often leading to significant damage, such as data breaches, system takeovers, or the spread of malware. 

The unpredictability and stealth of zero-day attacks make them particularly challenging to detect and mitigate, putting businesses, governments, and individuals at high risk.

In many ways, they function like a hidden trapdoor that provides unfettered access to malicious actors, who can use it for a variety of harmful purposes, from espionage to launching widespread attacks.

The Stuxnet Story

One of the most infamous examples of a zero-day exploit is the Stuxnet attack, which targeted Iran’s nuclear facilities in 2010. 

The zero-day exploits used by Stuxnet included:

1. Remote code execution on systems with printer sharing enabled
2. The LNK/PIF vulnerability, which allowed file execution when an icon was viewed in Windows Explorer
3. Two escalation of privilege vulnerabilities

Stuxnet also exploited a zero-day flaw in the Siemens PLCs (Programmable Logic Controllers) that were the primary target of the attack.

The use of multiple zero-day exploits in a single piece of malware was unprecedented at the time, highlighting the sophisticated nature of Stuxnet and its status as one of the first known cyberweapons.

Stuxnet went unnoticed for a long time because it was tailored to remain undetected while it caused physical damage to centrifuges. This cyberattack demonstrated the potential of zero-day exploits to affect not just data and software, but critical infrastructure as well. 

The Stuxnet story highlighted how powerful and destructive these exploits could be when used strategically.

How Zero-day exploits are discovered

Zero-day vulnerabilities are often uncovered through various methods. Security researchers might stumble upon them accidentally while testing or analyzing software. Hackers, on the other hand, may discover these flaws through deliberate searching or by reverse-engineering software code to find weak points. 

Additionally, automated tools can scan systems for overlooked vulnerabilities. Whether by chance or intent, the discovery of a zero-day exploit presents a critical moment, it’s a race between ethical researchers and malicious actors to either patch or exploit the flaw.

Regular vulnerabilities vs. zero-day exploits

Regular vulnerabilities are weaknesses in software that are publicly known, often identified through audits, user reports, or bug bounty programs. Once discovered, vendors typically issue patches or updates to fix them, enabling users to protect their systems by keeping software up to date.

Zero-day exploits, on the other hand, are vulnerabilities that remain unknown to the vendor and the public. Attackers exploit these flaws before they can be patched, leaving systems defenseless. Unlike regular vulnerabilities, where mitigation steps are readily available, zero-day exploits pose a unique challenge by bypassing traditional defenses, often causing significant damage before detection.

This critical distinction underscores the importance of proactive measures, like behavior-based threat detection, to safeguard against these unpredictable threats.

How zero-day exploits are developed and used

Hackers developing zero-day exploits use advanced techniques to uncover vulnerabilities and weaponize them for targeted attacks. This process involves multiple stages, from discovering weaknesses in unpatched code to delivering malicious payloads for maximum impact.

1. Discovery of vulnerabilities: Hackers reverse engineer software or analyze source code to uncover bugs or weaknesses unknown to developers. These flaws, hidden within unpatched code or third-party libraries, serve as the foundation for the exploit.
2. Analysis and verification: Once a vulnerability is found, attackers verify its validity by testing whether it can be exploited without detection. This involves creating a proof-of-concept to ensure the flaw can bypass security mechanisms.
3. Weaponization: The exploit is crafted into a malicious payload, customized to take advantage of the vulnerability. This payload is fine-tuned to compromise specific systems, platforms, or software versions.
4. Delivery methods: Hackers embed the payload into phishing emails, malicious websites, or infected applications to deliver the exploit. Social engineering is often used to ensure targets interact with the infected medium.
5. Execution and impact: Once deployed, the exploit executes its intended action, such as unauthorized access, data theft, or system disruption, while remaining undetected due to its zero-day nature.
6. Commercialization: Many zero-day exploits are sold on dark web markets to cybercriminals or nation-state actors, making them accessible to a broad range of attackers and amplifying their threat potential.

Zero-day brokers: the black market for exploits

Zero-day brokers act as intermediaries between vulnerability discoverers and buyers, often facilitating the sale of zero-day exploits. These brokers typically operate in private networks or the dark web, where they offer vulnerabilities for sale to cybercriminals, nation-states, or organizations. Prices for zero-day exploits vary depending on the severity and target, with high-profile vulnerabilities fetching large sums.

While some brokers sell vulnerabilities to security firms for defensive purposes, most deal in exploits for malicious use, increasing the risk of targeted attacks. This underground market makes zero-day vulnerabilities even more dangerous, as they can be weaponized and used by bad actors to inflict widespread damage. In an interview for Darknet Diaries, Nicole Perlroth, a cybersecurity and digital espionage reporter for The New York Times, highlighted how Argentina had become “this big outsourcing hub for exploit development,” noting that “this is where governments and front companies and brokers came to purchase zero-day exploits that they could use for their stockpiles of offensive cyber-espionage tools.”

Zero-Day exploits in the context of APTs (advanced persistent threats):

Zero-day vulnerabilities are a critical tool for advanced persistent threat (APT) groups, often used in long-term infiltration campaigns. These threat actors, typically state-sponsored or highly organized, exploit unknown vulnerabilities to gain unauthorized access to high-value targets like government agencies, critical infrastructure, or corporations.

APTs leverage zero-day exploits to infiltrate systems undetected, facilitating espionage, data theft, or sabotage. The stealth of zero-day vulnerabilities allows these groups to maintain persistent access over extended periods, often evolving their attacks to avoid detection. By using zero-day exploits, APTs achieve high success rates in cyber espionage, often without immediate counteraction from their targets until a patch is developed.

Mitigation and detection of zero-day exploits:

To combat zero-day exploits, organizations rely on advanced techniques such as Intrusion Detection Systems (IDS) and Intrusion Prevention Systems (IPS), which can be tuned to detect anomalies in network traffic and system behaviors. These systems monitor for unusual patterns that might indicate exploitation attempts, even before a patch is released. Behavioral analysis is another crucial tool; instead of relying solely on known attack signatures, it focuses on detecting abnormal activities, such as irregular file access or privilege escalations, that could signal an attack. Proactive threat hunting also plays a key role, with security teams using tools like endpoint detection and response (EDR) systems to search for signs of zero-day exploits before they fully unfold. By combining these methods, organizations can enhance their ability to identify and mitigate zero-day threats early.

Advanced tools and technologies for protection:

To defend against zero-day exploits, organizations rely on advanced security tools and technologies that provide early detection and effective mitigation. Endpoint Detection and Response (EDR) tools play a critical role in identifying signs of zero-day exploits by monitoring and analyzing activities on endpoints in real time. These tools can detect unusual behaviors, such as unexpected file changes or privilege escalation, which are common indicators of exploit attempts.

Sandboxing is another vital technology, allowing potentially malicious files to be executed in isolated, virtual environments. This lets security teams observe suspicious behaviors, such as system modifications or network communication, before allowing these files to interact with live systems. By observing these actions in a controlled setting, it’s easier to identify malicious behavior without risking a full-blown system compromise.

Automated patch management systems are also essential in minimizing the impact of zero-day vulnerabilities. These tools help organizations quickly apply patches once they become available, reducing the window of vulnerability and ensuring systems are protected as soon as a fix is released. By automating patch deployment, these systems reduce human error and speed up the remediation process, making them crucial in minimizing the damage caused by zero-day exploits.

The future of zero-day exploits and detection

Zero-day exploits will continue to pose significant threats, as they remain one of the most effective tools for cybercriminals and APT groups alike. The ability to exploit unknown vulnerabilities undetected for extended periods makes them a persistent challenge for cybersecurity professionals. 

However, with advancements in technology, we are beginning to see how AI and machine learning can transform the detection and prevention of zero-day exploits. These technologies can process vast amounts of network traffic and historical data to identify unusual patterns and predict potential exploits before they occur.

As AI and machine learning continue to evolve, they offer a promising solution for enhancing real-time detection, making it possible to catch these exploits earlier and with more precision than traditional methods. 

By analyzing complex datasets, AI systems can identify subtle anomalies that human analysts might miss, providing an additional layer of protection in the fight against increasingly sophisticated cyber threats. The integration of AI-powered tools into cybersecurity practices could soon revolutionize how we mitigate the risks posed by zero-day exploits, helping organizations stay one step ahead of attackers.

Prevention: How to reduce the risks of zero-day exploits

Mitigating the risk of zero-day security exploits starts with strong cybersecurity hygiene. Keeping all software and systems up to date ensures that known vulnerabilities are patched, leaving fewer opportunities for exploitation. 

Using firewalls and intrusion detection systems adds an extra layer of defense by monitoring and controlling incoming and outgoing traffic. Employing reputable antivirus software with behavior-based detection can help identify and neutralize suspicious activity, even from unknown threats. 

These foundational steps, combined with a proactive security approach, significantly reduce the likelihood of falling victim to zero-day exploits.

While zero-day exploits are challenging to prevent, organizations can take steps to mitigate risks, particularly by leveraging tools like Atera for effective patch management and defense. 

Here’s an expanded look at how to defend against zero-day threats, with a focus on Atera’s capabilities:

Defending against zero-day threats with Atera

Implement robust security practices and regular updates

Atera’s automated patch management plays a crucial role in maintaining up-to-date software across an organization’s network. By continuously scanning for vulnerabilities and missing patches, Atera ensures that systems are protected against known exploits, reducing the attack surface for potential zero-day vulnerabilities.

• Automated scanning: Atera performs an in-depth analysis of the entire software inventory across every connected device, identifying potential vulnerabilities in real-time.
• Customized deployment: IT managers can create tailored schedules for each endpoint, optimizing the patch management process for different device groups.

Use advanced monitoring and threat detection systems

Atera’s remote monitoring and management (RMM) capabilities provide advanced threat detection:

• Continuous monitoring: The Atera agent maintains regular heartbeat connections, allowing for constant surveillance of network activity.
• Intrusion detection: Atera can function as an intrusion detection system (IDS), monitoring networks for malicious activity.

Employ a defense-in-depth strategy

A multi-layered security approach is essential for protecting against zero-day threats. Atera contributes to this strategy by:

• Endpoint protection: Ensuring all endpoints are consistently updated and monitored.
• Network monitoring: Detecting suspicious network activities that could indicate a zero-day exploit attempt.

Rapid response to new threats

Atera’s platform allows for quick response to newly discovered threats:

• Immediate patch deployment: When a new vulnerability is discovered, Atera can rapidly deploy patches across the network.
• Custom patch criteria: IT teams can search and deploy patches based on specific criteria, ensuring critical updates are prioritized.

By leveraging Atera’s comprehensive patch management and monitoring capabilities, organizations can significantly enhance their defense against zero-day threats. While no solution can guarantee complete protection, Atera’s automated and customizable approach provides a robust foundation for a proactive security stance.

Ready to level up your cybersecurity posture? Try Atera for free, no credit card required!