Firewalls are designed to filter traffic based on predefined security rules and can effectively prevent attacks such as Buffer Overflow, SYN Flood, and SQL Injection by blocking malicious packets and traffic patterns. However, firewalls cannot prevent Network Bandwidth Saturation, which occurs when an excessive amount of traffic consumes all available bandwidth, leading to network congestion. This type of attack, often associated with Distributed Denial of Service (DDoS), requires different mitigation strategies such as traffic rate limiting, DDoS protection services, and increased bandwidth capacity.