[squid-users] http_access by passed

Hi all, i need your help.
I cant block access to some sites when users using old versions of Netscape
Communicator 4.7, 4.8 enters this kind of urls
http://www.google.com.ar%00@www.bangbus.com/

I have tried this
acl 1rule url_regex -i bangbus

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http_access deny 1rule  (as the first http_access line !!!!)
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And they can access anyway:
1116857165.790    386 *******  TCP_MISS/200 4330 GET
http://www.google.com.ar%00@www.bangbus.com/  *******  DIRECT/66.230.129.242
text/html
i have also try to block the "%00@"  in url_regex, dstdom_regex,
urlpath_regex....and it didnt work.
How can i block this requests ?
Thanks
Galle