What is a Zero-Day-Exploit?

A Zero Day, often called "0day," is a security vulnerability in software that is not yet known to the developers. A Zero-Day exploit refers to the exploitation of such a vulnerability by attackers. The term comes from the fact that developers had "zero days" to fix the vulnerability. When a Zero-Day exploit is published, it sometimes takes only minutes before botnets and hacker groups/APTs exploit the vulnerability and globally infiltrate companies. Therefore, Zero-Day exploits are one of the biggest threats to IT security.

How does a Zero-Day Exploit work?

The functionality of a Zero-Day exploit depends on the type of security vulnerability. Generally, there are various methods attackers use to exploit such vulnerabilities to infiltrate a system. It's common to see multiple security vulnerabilities combined to make an attack more effective.

The Process of a Zero-Day Attack

1. Software Release:
   A developer releases an application or update with an unknown security vulnerability. "Unknown" in the sense that it exists in the source code and no one has noticed it.
2. Discovery by the Attacker:
   The attacker finds the vulnerability through scanning or code analysis. APTs tend to monitor interesting open source projects and thoroughly analyze every patch.
3. Exploitation of the Vulnerability:
   The vulnerability is exploited using tools or custom code. Programming languages like Python or Golang are used to write small exploits.
4. System Attack:
   The Zero-Day exploit is used to compromise the target system. APTs often then spread through internal networks and place malware and backdoors.
5. Detection and Patching:
   The security vulnerability is discovered and reported to the developers, who then provide a patch. Administrators worldwide try to install the patch as quickly as possible. In parallel, the system is checked for damage.

Why are Zero-Day Exploits dangerous?

Zero-Day exploits are dangerous because they are unknown and can therefore remain unnoticed for a long time. This gives attackers the opportunity to cause damage or steal data undisturbed.

Advanced Persistent Threats (APTs)

With unknown vulnerabilities, attackers can infiltrate systems long-term and establish so-called Advanced Persistent Threats. They leave backdoors and move undetected through the network. Often, such threats are only discovered after months.

How can a Zero-Day Exploit be detected?

Although Zero-Day exploits are difficult to detect, there are strategies to identify suspicious activities. This should start with unusual behavior in the network or on endpoints. However, it's important to mention that often the security vulnerability itself is not found, but rather the effects of the successful attack through this vulnerability. If the victim has enough information, access logs, and event logs, the initial vulnerability can sometimes be identified.

Behavior-based Monitoring

Potential attacks can be detected based on malware behavior. Behavior-based monitoring analyzes activities in the system and identifies anomalies.

Hybrid Detection Methods

A combination of different detection methods increases the chance of discovering Zero-Day exploits. Both statistical data and behavioral analyses are used.

How can you protect against Zero-Day Exploits?

There are several ways to prevent Zero-Day attacks and minimize their impact. Therefore, it's important that both organizations and individuals pursue comprehensive security strategies.

Proactive Security Measures

1. Use Antivirus Software:
   Protects against known and unknown malware through advanced detection methods. At least that's what the vendors say - in reality, antivirus programs have a very poor detection rate for Zero-Day exploits.
2. Configure Firewalls:
   Blocks unauthorized access and prevents potential attacks from the network. This point is often underestimated. A well-configured firewall might not prevent infection, but it can make it harder to exfiltrate data and/or ensure this is noticed.
3. Regular Updates:
   Always install the latest patches to close known security vulnerabilities. Especially in internal networks, unfortunately, patching is too often neglected.
4. Check System Settings:
   Ensure systems are correctly configured to make attacks more difficult.