What is a Zero-Day Vulnerability and How to Defend Against It?

A Zero-Day Exploit refers to a security vulnerability in software or hardware that is unknown to the software vendor or developer, and the system owner is unaware of its existence. At the time, there are no patches or fixes available for it. 

The term "Zero-Day" comes from the fact that the developer has “0 days” to prepare or fix the system before the exploit is used for an attack. 

How to Identify a Vulnerability

One key method for detecting vulnerabilities is by monitoring Threat Intelligence & Advisory from security news sources such as CISA, NVD, MITRE CVE, and security advisories from manufacturers (Microsoft, Cisco, Adobe, etc.), including Threat Feeds that are integrated with SOC/SIEM. 

If you're unsure where to start, at BMSP, we have a Threat Intelligence Platform that operates in Real-Time, providing instant alerts about threats and Zero-Day Vulnerabilities as soon as they are disclosed or exploited. 

Real-World Example

• Microsoft Exchange Zero-Day Microsoft detected multiple Zero-Day exploits targeting Microsoft Exchange Server 2021 (On-Premises) in a targeted attack by the HAFNIUM group, using vulnerabilities CVE-2021-26855, CVE-2021-26857, CVE-2021-26858, and CVE-2021-27065. 

• Zoom Zero-Day In April 2020, a Zero-Day vulnerability was found in Zoom that allowed attackers to send UNC path injectionlinks via chat. If the user clicked on the link, it would send Windows login credentials and NTLM hashes to the attacker’s server, enabling a dangerous phishing attack. 

How to Prevent Zero-Day Exploits

1. Vulnerability Scanning

   ▸ Use vulnerability scanning tools to detect unpatched vulnerabilities or those that might be exploited in the future. 

   ▸ Regularly scan systems to identify vulnerabilities that remain unpatched and can be targeted. 

2. Patch Management

   ▸ Once a Zero-Day is disclosed and a patch is released by the vendor, update your system immediately. 

   ▸ Implement Automated Patch Management to ensure all tools are updated quickly. 

   ▸ Configure systems for automatic updates, especially for publicly exposed software like web servers, VPNs, or internet-facing applications. 

3. Virtual Patching

   ▸ If there’s no patch available from the vendor or it can't be applied immediately, use Virtual Patching to protect against exploits without updating the software. 

   ▸ Use tools like Web Application Firewalls (WAF) or Intrusion Prevention Systems (IPS) to temporarily close the vulnerability. 

   ▸ Enhance network filtering and detection to block exploit payloads. 

4. Behavioral Detection & Response

   ▸ Use Endpoint Detection and Response (EDR) to detect and identify unusual behaviors within systems that may result from a Zero-Day exploit.

   ▸ SIEM (Security Information and Event Management) can help detect and respond to incidents during an attack.

5. Access Control

   ▸ Implement strict Access Control policies, such as Least Privilege Access, to limit user rights within the system, reducing the risk of a Zero-Day exploit.

   ▸ Continuously monitor system access and usage. 

Zero-Day Vulnerabilities are among the most significant risks because they are unknown and have no immediate fix. Prevention should focus on detecting behaviors, making systems resilient, and responding quickly once a vendor releases a patch. 

At BMSP, we understand that Zero-Day Vulnerabilities are one of the most critical threats, as they are unknown, lack patches, and are difficult to prevent. That’s why we offer 24/7 monitoring and threat alerts, along with risk analysis to advise on the best practices for securing systems effectively in all situations. 

Contact BMSP for more information about our Threat Detection Solutions at marketing@bangkokmsp.com.