I guess this is one of the new ones I keep hearing about (Netsky, Bagel, et al). It seems to be making really malformed http requests: you can see that they are running about 6 kbytes on size (an average line is about 160 bytes).
# tail -1 httpd-access.log | wc
1 12 6405
Just a lot of crap following a NULL.IDA? query. Interestingly, it’s all coming from one PC (located at 61.62.23.41) on Sony Network Taiwan Limited’s network.