These distributed denial of service attacks (DDoS) are facilitated by software tools designed to damage a computer network's ability to function by flooding it with useless commands and information, thus denying service to legitimate users

It seems to me that demonstrating in front of a business does not prevent people from entering. A DDoS attack is designed to shut the business down.

It is important to note the difference between a DDoS and DoS attack. If an attacker mounts an attack from a single host it would be classified as a DoS attack. In fact, any attack against availability would be classed as a Denial of Service attack. On the other hand, if an attacker uses a thousand systems to simultaneously launch smurf attacks against a remote host, this would be classified as a DDoS attack.

The major advantages to an attacker of using a distributed denial-of-service attack are that multiple machines can generate more attack traffic than one machine, multiple attack machines are harder to turn off than one attack machine, and that the behavior of each attack machine can be stealthier, making it harder to track down and shut down. These attacker advantages cause challenges for defense mechanisms. For example, merely purchasing more incoming bandwidth than the current volume of the attack might not help, because the attacker might be able to simply add more attack machines.

It should be noted that in some cases a machine may become part of a DDoS attack with the owner's consent. An example of this is the 2010 DDoS attack against major credit card companies by supporters of WikiLeaks. In cases such as this, supporters of a movement (in this case, those opposing the arrest of WikiLeaks founder Julian Assange) choose to download and run DDoS software.