I am not aware how the tangle architecture specifically is prone to Ddos. If you have any sources on that I would love to see them. 

Individual nodes can receive too many requests and be over-worked. The amount of nodes in the entire network can handle a very large load however. 

Here is a reddit post talking about the same subject:

https://np.reddit.com/r/Iota/comments/7egqk7/is_iota_really_ddos_resistant/dq4uvj9/