Dear Dan,
Thank you very much for your answer and suggestions. I've went to the access log and all the requests were given 404 error. After I've edited my .htaccess file using redirect handler and all the attacks have redirected to my home page. My website is hosted at Godaddy.com and their support team doesn't think my website has any infection. Is there anything that I could do to remove my domain from this malware domain list?