Help to understand that row of log

hi at all, it'my first post, i'm a newbie in webmaster
but i would like to know something about a strange rows that i find in the apache access log, something like that:

86.19.164.185 - - [10/Jun/2012:10:39:01 +0200] "K\xcc\xfb\xef\xb1$cl\vG\x12\\]\xdb\xe7\xf3\x81\x07+W\x1c\xfbqy;C\xce\xcf#\x9c\xdeM\x1c&\x1bU" 400 338 "-" "-"

94.41.71.125 - - [10/Jun/2012:19:25:43 +0200] "\xa1f\x98\xec" 200 45626 "-" "-"

186.124.61.185 - - [11/Jun/2012:03:29:26 +0200] "\xf1%\xb2uA:[<d\x15\xe6\xde\x15\xa8\x7f\x1b;m*\xf3\x8a3/H\x9f\xea\x17\xb4i\t\xd6\r\xa7t\x82\xc8;\xae\xe4\xca\xe7f" 400 338 "-" "-"

86.123.217.229 - - [11/Jun/2012:21:29:27 +0200] "\xb2[Z\xefR_\x0e;\xea\x8b\xbaH&\xebc\x88\xecP\xca\x9b\xb4\xef" 200 45626 "-" "-"

i found those rows with different sequence of code sometimes with the error 400 but sometimes with the return code 200

in the error.log there a correspondant row like

[Sun Jun 10 10:39:01 2012] [error] [client 86.19.164.185] Invalid URI in request K\xcc\xfb\xef\xb1$cl\vG\x12\\]\xdb\xe7\xf3\x81\x07+W\x1c\xfbqy;C\xce\xcf#\x9c\xdeM\x1c&\x1bU

for the accees.log row with the 400 return code
could someone explain what it mean?

my machine is a debian 5 vm with standard installation of apache2 with suhoshin (like installed from reposistory)
thank's a lot to all

Giorgio

 

The URI gibberish is likely some kiddie script.

There is however a more pressing issue.

No webmaster should allow any visitors whom fail to abide by RFC Protocol in identifying themselves with a "vaild" User-Agent.
Blank User-Agents are not vaild.

At the very end of your log lines are the following "-" "-".
The first portion is for a blank referral and is quite comon these days.
The second portion is the blank User-Agen and should be denied access to your site (s).

 

what language your site in and does it use non-latin characters in URLs? Sometimes robots get confused by unicoded URLs and trying to access such garbage looking urls that obviously don't exist on the server