Preventing unauthorized network access is critical for maintaining organizational security. The most effective strategies include implementing robust firewall systems that filter incoming and outgoing traffic. Network segmentation creates isolated zones to contain potential breaches, while strong access control policies ensure users only access necessary resources. Multi-factor authentication (MFA) adds an essential security layer beyond passwords. Regular software updates patch vulnerabilities that attackers might exploit. Employee training creates security awareness to prevent social engineering attacks. Intrusion detection systems monitor network activity for suspicious behavior. Virtual Private Networks (VPNs) secure remote connections, and wireless networks should use strong encryption protocols like WPA3. Regular security audits identify weaknesses before they can be exploited. These combined measures create a defense-in-depth approach that significantly reduces the risk of unauthorized access.