DOS attack against DNS?

I just started seeing thousands of DNS queries that look like some sort of DOS attack. One log entry is below with the IP obscured. client xx.xx.xx.xx#6704: query: z.tn.co.za ANY ANY +E When you look at z.tn.co.za you see a huge TXT record. Is anyone else seeing this attack or am I the lucky one? Is this a known attack? Roy