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Cybersecurity is becoming an internal and important part of a business's functioning as more and more enterprises are going online with their businesses. In recent years the cybersecurity scenario has changed completely as there is an exponential rise in cyberattacks on organizations. The pandemic has only added fuel to the fire. There is a constant battle between cybersecurity experts and malicious actors to outwit each other. Though some attacks can be thwarted or prevented some attacks are nightmares for developers and cybersecurity professionals alike. A zero-day attack falls in the latter category.

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## **What is a Zero-Day attack?**

A zero-day attack or a zero-day exploit is a successful attempt by hackers to find an exploit software and previously unknown network vulnerabilities. Unfortunately, software and network security systems have vulnerabilities and weak points that act as a backdoor or a window for hackers to launch a full-scale attack. These types of attacks are called zero-day attacks as the security experts, or the developers are completely unaware of the vulnerabilities in a system until an attack occurs. Hence the name zero-day attack since they have known about the weak points or vulnerabilities in a system for zero days. As soon as the attack occurs it is no longer a zero-day attack as now the developers know about the vulnerabilities which caused the attack.

Sometimes a developer knows about these vulnerabilities but is waiting for or developing a new software patch to counter these vulnerabilities and that is when a zero-day attack occurs. These are known as zero-day vulnerabilities.

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## **Why are zero-day attacks so dangerous?**

Zero-day attacks are dangerous because they rely quite often on unknown weak spots and vulnerabilities. The software developers can develop a patch in response to an attack but are helpless if an attack has already occurred. Zero-day attacks are usually launched as soon as software or a security system is released or used. 

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The attack exploits the unknown vulnerabilities, and it can be quite a while until the vulnerabilities are addressed giving the hacker a lengthy exposure window time. Much traditional protection or anti-virus systems are built to detect only the known vulnerabilities or tell-tale signatures or traces of a known cyber-attack. Hence the zero-day attacks become more potent as they can circumvent the protection system already in place. Since they attack unknown vulnerabilities not only can they stay undetected in a system for a long time but are also much more difficult to defend against as the developers are blind-sided by the nature of the attack. Zero-day exploits are highly valued bug bounty programs and fetch a good rate in the underground market as these attacks cause significant damage for a prolonged period.

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Organizations can undergo massive damages and losses like a data breach or data exposure of sensitive data, critical systems failure which will halt the business completely, and financial losses due to the business not functioning through penalties imposed by data privacy and patch management regulations.

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## **Type of Zero-day exploits**

There are several ways in which a zero-day exploit can be used. They are:

•  Spear Phishing: Emails with attachments embedded with malware and worms, designed specifically for a target audience, and sent from a known apparent known source to trick them into divulging sensitive information

•  Phishing: Malware-embedded emails, messages, or malicious links that lure the targeted and  unwitting users to click on them which causes data breaches and cookie sessions hijacking

•  Exploit kits: Exploit kits are automated threats that use compromised sites to divert web traffic, scan for vulnerable browser-based applications, and run malware. Exploit kits are highly automated in nature and have become popular among hackers and malicious actors.

• Compromising a system, server, or network: Compromising the systems, servers, or networks through brute force penetration, misconfigurations, or attacking an exposed surface.

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## How are Zero-day attacks detected?

The most effective and efficient way of detecting a zero-day attack is for developers themselves to detect any risks and vulnerabilities and work on them before the hackers exploit them. If the vulnerabilities are not detected on time zero-day attack unfolds and then it is too late. A good vulnerability detection system helps to detect a possibility of a zero-day attack.

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The developers should follow the best hygiene practices to stop all types of attacks before they start. Performing penetration testing to determine or detect inherent risks and vulnerabilities can allow the detection of zero-day attacks.

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The organizations can also offer bug bounties wherein good hackers or ethical hackers who detect vulnerabilities and alert the organization are handsomely rewarded.

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## How to defend against zero-day attacks?

It is difficult to defend against zero-day attacks due to their unknown and unpredictable nature. Organizations that have a robust security system and who have built their security system around known and already patched flaws too are vulnerable to zero-day attacks. Hence it is advised to have a proactive defense approach as compared to a rigid one. Here are some countermeasures.

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Practice regular patch management: Applying updated patches to systems and servers as soon as they are life reduces the number of flaws and the attack surface which a hacker can exploit. Organizations should make it a point to regulate zero days in their patch management as well as incident response and remediation strategies.

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Secure email gateways, servers, and networks: Email gateways, servers, and network systems are prone to attacks and can be used as a pivot to move laterally into the security system of an organization. Hence securing exposed gateways, servers and networks are of utmost importance.

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Implement the least privilege principle: Restricting and securing network access and administrative tools access to only the employees who use them frequently is a good and safe practice. This way the organization can ensure that there is no unauthorized access to sensitive data and no unwitting data breaches.

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Practicing best cybersecurity hygiene: Covering basic cybersecurity hygiene and fostering a culture where cybersecurity is deemed important also helps in thwarting zero-day attacks. Increasing User awareness of threats and attacks through training programs as well as training employees to handle an attack situation go a long way in the prevention and detection of attacks.

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Enabling Multi-layered security defenses: Researching the threat landscape and implementing an additional layer of security help organizations in preventing attacks. Measures such as a strong firewall, vulnerability detection system, intrusion detection, and prevention system, securing endpoints to filter and keep tabs on data traffic, application control, and anomaly detection can be applied for a strong security layer.

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## How to recover from a Zero-day attack?

The only solution to recover from zero-day attacks is software patches. Due to their unknown nature, they are hard to predict and hence to defend against. Once a zero-day attack occurs, an incident report should be filed immediately, an attack analysis should be carried out along with a vulnerability assessment. Based on the analysis a software patch should be developed that helps in closing or bandaging these vulnerabilities. The developers should ensure that the exposure window that is the time between detecting a vulnerability and developing a patch to counter the vulnerability should be nominal to minimize the impact of the attack and to ensure there are no significant damages to the organization.

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*Also Published [here](https://www.linkedin.com/pulse/what-zero-day-attack-how-defend-against-securetriad/?trackingId=3TikTCjehCQ4%2BkRPJzlY0w%3D%3D)*

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