A denial-of-service (DoS) attack is intended to make the targeted machine reach its maximum load (capacity to serve requests) quickly by sending numerous false requests so the target system denies further genuine requests.

Flood attacks and buffer overflow attacks are two categories of DoS. With flood attacks, the attacker saturates the target server by generating enormous traffic to the server, causing the target server to end up in DoS.

On the other hand, a buffer overflow attack is intended to target a machine and make that machine consume all available memory or hard disk space, or cause high usage of the CPU. This result in various consequences, such as the system becoming slow to respond or sluggish in its behavior, and there may even be a situation in which the targeted system will crash, creating potentially catastrophic results.