I noticed some slowing on my server earlier today and when I looked into the log files, in between legitimate site requests are blank requests like this:
108.212.75.60 - - [13/Sep/2012:16:56:28 -0400] "-" 408 - "-" "-"
108.212.75.60 - - [13/Sep/2012:16:56:28 -0400] "-" 408 - "-" "-"
108.212.75.60 - - [13/Sep/2012:16:56:28 -0400] "-" 408 - "-" "-"
108.212.75.60 - - [13/Sep/2012:16:56:28 -0400] "-" 408 - "-" "-"
Does anybody have any idea what these might be or how I can prevent them? They seem to be taking up a decent chunk of my server resources.