What is a Layer 4 DDoS attack and how does it differ from other types?

A Layer 4 DDoS attack targets the transport layer (TCP/UDP) of the OSI model. Unlike Layer 3 attacks which target IP addresses, Layer 4 attacks exploit weaknesses in TCP/UDP protocols to overwhelm the target server with a flood of packets. Common techniques include SYN floods, UDP floods, and ICMP floods. This differentiates it from Layer 7 attacks which target application-layer vulnerabilities, making Layer 4 attacks generally more difficult to filter with simple firewalls.