Bad request unknown in daily log

[Wynand]

Hi,

On one of our DA servers one of the daily logs (2014-Dec-10.log) is getting spammed with

10/12/2014:09:45:56 195.*.*.*8 BAD REQUEST unknown
10/12/2014:09:45:56 195.*.*.*8 BAD REQUEST unknown
10/12/2014:09:45:56 195.*.*.*8 BAD REQUEST unknown
10/12/2014:09:45:56 195.*.*.*8 BAD REQUEST unknown
10/12/2014:09:45:56 195.*.*.*8 BAD REQUEST unknown

Same IP so I could nullroute, but how can I determine the source of these messages?