im on the bt network. and i must say its one of the worst networks for virises worms.
your knoppix machine wont be in any danger of getting a viruses or worm for various reasons.
knoppix 3.7 uses the latest stuff that it can. most viruses and worms out there are aimed at windows users because 1 a normal windows user doesnt know how to upgrade there outdated software 2 even if they did they wouldnt.

i would really advise to getting a router this will handle pppoe/a for you and dial into your isp account and log you on. it will also act as a firewall at the same time so it will protect windows machines.

as for in the mean time. try and find a program on knoppix that uses pppoe or pppoa then give it your infomation you should be able to sign in with no problems.how ever knoppix doesnt allways go so well when it comes to modem so you might not beable to connect if you cant connect then your best bet would be to get a some ethernet cards some cables and a router. and let your router do the connecting for you.