"It is a sad fact that it has been somewhat difficult to connect to DALnet for some time. There are several reasons for this, including ongoing attacks and a loss of servers." notes the DalNET Web site
You really have to ask yourself WHY? What's the fun in this kind of attack? What exactly do you get out of it? I can understand personal revenge, but this is just the cyber equivalent of someone vandalising a bus shelter just for the sake of it.
"This assault on our servers has rendered many of them inoperable and has virtually closed DALnet to normal use. We have no information on who is behind these attacks or what they hope to gain by depriving users of our services and causing extreme inconvenience (and incurring significant cost) to our hosts," notes the DalNET Web site
Apparently, the normal average of 140,000 users has been reduced to a mere 2000. Currently the future of DalNET is in question.
More here, and here.