What are zero-day attacks?
A zero-day attack is a cyber attack that exploits a previously unknown software vulnerability (My Pivots, 2022). The term “zero-day” refers to the fact that the vulnerability is not publicly known and there has been zero days to develop and release a patch.
Zero-day vulnerabilities exist in software products that are actively being used and supported. Attackers can take advantage of these vulnerabilities to execute malicious code and gain unauthorized access before the vendor is aware of the flaw. Since vendors do not know about the vulnerability, they cannot distribute patches or workarounds to protect users against exploits. This makes zero-day exploits highly dangerous.
When attackers discover a zero-day vulnerability, they can develop exploit code to leverage that vulnerability and launch attacks. The goal is often to install malware, gain control of systems, steal data, or cause other types of damage. Successful zero-day attacks can compromise both individual users and entire corporate networks.
Zero-day attacks are concerning because they circumvent traditional security measures. Firewalls, antivirus software, and other defenses are ineffective when the underlying software has an unknown flaw. This underscores the importance of proactive security measures in addition to reactive defenses.
The rising threat
Statistics show that zero-day attacks are becoming more prevalent over time. According to Cyber Security Statistics, the total number of zero-days recorded in the past 10 years has risen to 671. In Q3 2021 alone, zero-day malware increased to 67.2%, up 3% from the previous quarter.
There have been many high-profile examples of damaging zero-day attacks. In 2017, the WannaCry ransomware attack exploited a Windows vulnerability to infect over 200,000 computers globally. In 2019, a zero-day vulnerability in WhatsApp allowed attackers to install spyware and access data on victims’ phones. And in 2021, multiple zero-days in Microsoft Exchange Server allowed threat actors to compromise tens of thousands of organizations worldwide before patches were released.
Limitations of traditional security
Traditional security measures like antivirus software and firewalls are ineffective at stopping zero-day attacks. This is because these solutions rely on recognizing attack patterns against known vulnerabilities. With zero-days, the vulnerability itself is unknown, so there are no attack signatures to look for.
Antivirus programs are reactive in nature – they can only block threats once a signature has been created for that threat. This means they provide little protection against brand new threats that antivirus vendors have not yet analyzed and created definitions for.
Network firewalls also use pattern matching to block known malicious traffic. Since zero-days exploit unknown flaws, the attack traffic doesn’t match any known malicious pattern and will bypass firewall protection.
According to one report, despite spending more on traditional security measures every year, attackers are able to penetrate security defenses and compromising networks at will using zero-day exploits (source). Clearly, new and more proactive strategies are needed to defend against the rising threat of zero-day attacks.
Proactive defenses
One of the most promising approaches for defending against zero-day attacks is utilizing intelligent threat detection systems powered by machine learning and artificial intelligence. Rather than relying solely on signatures of known threats, these systems analyze patterns and anomalies in behavior to identify activity that resembles zero-day exploits or attacks. As explained in research from Darktrace, “Using Self-Learning AI to defend against zero-day and N-day attacks,” AI and machine learning solutions can be “trained on ‘self’ to detect abnormal deviations in behavior that might indicate an unknown threat.”
Advanced machine learning algorithms have the capability to detect zero-day threats that appear different on the surface but share fundamental features with known attacks. The algorithms identify common tactics, techniques, and procedures used in exploits. According to a recent study titled “A review of machine learning-based zero-day attack detection: challenges and future directions,” these intelligent systems “can detect zero-day attacks by learning normal behavior patterns and identifying significant deviations from them.”
By monitoring for unusual account activity, network connections, code execution, and other anomalous events, organizations can gain visibility into threats that traditional signature-based tools would likely miss. AI and machine learning offer the adaptive intelligence needed to keep pace with the rapidly evolving threat landscape.
Software development best practices
Following secure development practices when creating software can significantly reduce the risk of vulnerabilities that could lead to zero-day exploits. Some key best practices include:
- Input validation – Rigorously validating all input data can prevent injection attacks and other exploits of unchecked data.
- Principle of least privilege – Only granting the minimum privileges needed reduces the attack surface.
- Security focused design – Considering security from the beginning and threat modeling helps avoid overlooked risks.
- Code reviews and testing – Rigorous code reviews and security testing by experts can uncover flaws before release.
- Static analysis – Automated tools can help detect bugs and weaknesses in code.
Adhering to secure development methodologies, design patterns, coding standards and best practices makes it much harder for attackers to find weaknesses to exploit. This proactive approach is essential for minimizing zero-day vulnerabilities.
Regular patching and updates
Applying the latest patches and system updates is one of the most important ways to close vulnerabilities that could be exploited in zero-day attacks. According to Cynet, while patch management cannot prevent unknown zero-day attacks, it can significantly reduce the window of exposure if a severe vulnerability is discovered. Patches fix known flaws in software code, so maintaining systems fully updated greatly reduces the attack surface.
Organizations should have an automated patch management system to ensure patches are tested and applied promptly across the environment. Verifying patches are installed through vulnerability scanning is also critical. Regular patching cycles, such as monthly or quarterly, are recommended. While zero-days will still slip through, regular patching combined with other proactive measures makes zero-day attacks much harder to succeed.
User education and training
One of the most important ways to defend against zero-day attacks is through comprehensive user education and training. Since zero-day exploits often rely on social engineering tactics or users unknowingly downloading malware, employees represent a major vulnerability. By establishing a strong cybersecurity awareness training program, organizations can go a long way toward preventing successful zero-day attacks.
Training should educate end users on cybersecurity best practices for identifying potential threats. This includes learning how to spot suspicious emails, questionable downloads, unsafe browsing habits, risky website access, and other common vectors for malware or intrusion. Users should understand phishing tactics, the risks of clicking unknown links, best practices for password security, and how to identify irregular system activity that may indicate infection.
Beyond training, organizations should also implement simulated phishing and social engineering tests to keep employees alert. Cybersecurity training cannot be treated as a one-time event, but must be an ongoing program as threats evolve. When users are empowered with knowledge and resources to proactively avoid risky cyber behavior, organizations become much harder targets for zero-day exploits and intrusion attempts.
Incident response preparation
Having an incident response plan in place can help you react swiftly and effectively in the event of a zero-day attack. This plan should outline steps for quickly analyzing and containing new threats when they occur before they can spread and cause damage. The key aspects of an effective incident response plan include:
- Establishing procedures for prompt threat detection and analysis.
- Defining containment strategies to isolate impacted systems.
- Specifying steps for eradicating the threat from systems.
- Creating plans for recovering from the incident and restoring normal operations.
Incident response teams should regularly test and update plans to account for new attack methods. They can also benchmark against industry best practices for responding to zero-days, like those outlined in the SANS Institute’s Responding to Zero Day Threats guide.
With robust preparation, organizations can quickly mobilize to analyze, contain and eradicate zero-day threats when they emerge to minimize disruption.
Accepting some level of risk
Even with best practices, zero-days still pose some level of unavoidable risk. As Reddit user points out, “Zero day risk management with DMZ clients and firmware push all need to align” (source). The key is focusing on minimizing attack surface and mitigating potential impact.
Organizations should conduct risk assessments to identify their most critical assets and vulnerabilities. Efforts can then focus on strengthening protections around those high-value targets. Utilizing network segmentation, least privilege principles, encryption, and other defenses makes exploitation more difficult.
It’s also essential to have an incident response plan ready in case attackers do successfully exploit a zero-day. Rapid detection, containment, eradication and recovery capabilities can greatly limit damage. Accepting some baseline of risk is inevitable, but organizations can still take steps to substantially reduce their exposure.
The future of zero-day defense
Despite the challenges, emerging techniques provide hope for better defending against zero-day attacks in the future. Bug bounty programs that incentivize ethical hackers to find and report vulnerabilities are becoming more widespread. According to one report, bug bounties identified over 4,000 vulnerabilities in 2020 alone, before they could be exploited (https://fastercapital.com/topics/the-future-of-zero-day-attacks.html).
Formal program verification and automated code auditing tools are also advancing. While not foolproof, these techniques can mathematically prove code adheres to certain security properties or use AI to flag suspicious patterns. Coupled with diligent code reviews and testing, they may eliminate certain classes of vulnerabilities that lead to zero-days. Ongoing research and industry adoption of these methods can potentially improve software assurance.
Ultimately, the cat-and-mouse game between attackers and defenders continues. While zero-days likely can’t be stopped entirely, a combination of secure development, defensive layers, and rapid response capabilities can reduce organizational risk. An adaptable cyber resilience strategy is key for managing the impact of the inevitable zero-day.
