Unusual entry in Apache logs

[Neil Dickey <neil () geol niu edu>]

I have of late seen a few entries such as this ...

125.224.192.192 - - [29/May/2008:09:15:34 -0500] "\x05\x01" 501 3100 "-" "-"

... in my Apache webserver logs.  They are the only entry in
the log for the particular source IP; that is, they don't
represent an anomaly in an otherwise normal session.  Such
entries record the only contact made by the source IP.

GOOGLE hasn't told me anything interesting; does anyone know
what this is?

Many thanks for any ideas.

Best regards,

Neil Dickey, Ph.D.
email: neil () geol niu edu
Research Associate/Sysop
Geology Department
Northern Illinois University
DeKalb, Illinois, U.S.A.
60115