Glossary Home

Zero-Day Attacks

What is a zero-day attack?

A zero-day attack is a type of cyberattack that targets a software vulnerability that is unknown to the software vendor or developer at the time of the attack. Since no patch or fix exists, attackers exploit the flaw before it is discovered and resolved, often leading to unauthorized access, data breaches, or malware infections.

In simple terms, a zero-day attack is like a stranger walking through a door you thought was locked. Without your knowledge, they slip in through a security flaw you didn't even know existed.

How do zero-day attacks work?

A zero-day attack is not a singular event; it unfolds through several distinct phases:

1. Vulnerability discovery: Hackers identify a previously unknown flaw or weakness in a system or application.
2. Exploit development: They then create a malicious exploit that specifically targets the vulnerability.
3. Attack launch: The attacker uses the exploit to gain unauthorized access to vulnerable systems, often by deploying malware or other malicious code.
4. Impact: The attacker can then use the compromised system for various malicious purposes, including data theft, system disruption, or launching further attacks.

Why are zero-day attacks so dangerous?

Zero-day attacks are particularly dangerous because they exploit unknown vulnerabilities for which no defenses or patches exist yet.

• They are unpredictable, hard to detect in real-time, and allow attackers to infiltrate systems silently.
• Organizations often realize the attack only after significant damage is done — including data theft, system downtime, or reputational harm.
• Recovery is complicated since identifying the breach, tracing the point of entry, and regaining control can be challenging and time-consuming.

Who are the major targets of zero-day attacks?

• Government agencies
• Large enterprises
• Critical infrastructure systems
• Individuals with access to sensitive data

Examples of zero-day attacks

Stuxnet (2005-2010)

Stuxnet serves as a prominent example of a zero-day exploit's potential impact. Discovered in 2010, this sophisticated computer worm specifically targeted industrial control systems, notably Siemens' Step7 software running on Microsoft Windows. By exploiting multiple zero-day vulnerabilities, Stuxnet infiltrated programmable logic controllers (PLCs) used in Iran's uranium enrichment facilities. Once inside, it manipulated the PLCs to alter the operation of centrifuges, causing them to spin at destructive speeds while reporting normal functioning to monitoring systems. This covert sabotage led to significant physical damage, reportedly destroying nearly one-fifth of Iran's nuclear centrifuges. Stuxnet's deployment marked a significant moment in cyber warfare, demonstrating how digital tools could cause tangible damage to critical infrastructure.

Operation SyncHole (2024–2025)

Operation SyncHole is a recent example of a zero-day attack. In this recent espionage campaign, the infamous North Korean threat group Lazarus targeted multiple organizations in the software, IT, finance, and telecommunications sectors in South Korea. The threat actor combined a watering hole attack strategy with an exploit for a vulnerability in a file transfer client that is required in South Korea to complete certain financial and administrative tasks. Researchers have reported that the activity compromised at least half a dozen organizations between November 2024 and February 2025.

What are the impacts of zero-day attacks?

Zero-day attacks can have numerous adverse impacts, including:

• Data theft
• Unauthorized control and access to the network or system
• Damage to reputation
• Financial loss
• Shutdown of business operations
• Legal implications (due to lack of regulatory compliance)

Best practices for zero-day attack prevention

While zero-day attacks are challenging to prevent entirely, implementing these strategies can significantly reduce the risk and potential impact of such exploits.

• Use trusted and compliant software solutions: Always choose software from reputable vendors that follow recognized security standards (such as ISO 27001, GDPR, or SOC 2) and offer advanced security features. This reduces the likelihood of using products with hidden vulnerabilities.
• Implement advanced antivirus solutions: Use next-generation antivirus (NGAV) tools that detect unusual behavior patterns to identify potential threats.
• Implement email security solutions: Deploying robust email protection services, such as Zoho eProtect, helps detect and block malicious emails that could carry zero-day exploits, protecting users from phishing, malware, and other advanced threats.
• Monitor vulnerability reports: Regularly check trusted sources for newly discovered vulnerabilities and apply available patches promptly.
• Maintain rigorous patch management: Establish a systematic process to identify, test, and deploy patches to fix known vulnerabilities.
• Deploy Web Application Firewalls (WAF): Utilize WAFs to filter and monitor HTTP traffic between web applications and the internet, blocking malicious inputs.
• Apply the principle of least privilege: Ensure users have only the access necessary for their roles, reducing potential damage from compromised accounts.
• Employee training: Regularly educate staff on cybersecurity awareness, phishing recognition, and safe password practices.