Figure 1.10: DDoS Attack

If the requests are more than the maximum capacity that the server

can handle, then the server goes unavailable for further requests.

This is pretty common in the Internet shopping sites or organizations

offering online services. Many Blockchain backed cryptocurrency

exchanges have faced such attacks and have gone offline from time

to time. Hence, many public Blockchains have started moving from a

permissionless to a permissioned architecture. Let’s now discuss the

different levels of permissions in the Blockchain protocols.

1.8 Permission Levels

As shown in Figure 1.11, DLTs can be divided into four different

types on the basis of their permission levels, as follows: