Error Log Overflow

I'm not a proffessional programmer and I'm asking for your help. I'm using PHP and running Apache server and Mysql database server on my home network computer to serve my web site. My PHP error log is getting as big as more than 1MB daily. Looks like somebody is bombarding my site with strange requests constantly and I believe it is slowing my server. I'm correct? If so, how I can get rid of that?Below is example of my error log:
[Mon Mar 12 15:18:51 2007] [error] [client 218.206.249.116] client sent HTTP/1.1 request without hostname (see RFC2616 section 14.23): /
[Mon Mar 12 15:18:53 2007] [error] [client 218.206.249.116] client sent HTTP/1.1 request without hostname (see RFC2616 section 14.23): /
[Mon Mar 12 15:18:53 2007] [error] [client 218.206.249.116] client sent HTTP/1.1 request without hostname (see RFC2616 section 14.23): /
[Mon Mar 12 15:18:55 2007] [error] [client 221.195.36.78] client sent HTTP/1.1 request without hostname (see RFC2616 section 14.23): /
[Mon Mar 12 15:18:56 2007] [error] [client 221.195.36.78] client sent HTTP/1.1 request without hostname (see RFC2616 section 14.23): /
[Mon Mar 12 15:19:19 2007] [warn] (OS 121)The semaphore timeout period has expired. : winnt_accept: Asynchronous AcceptEx failed.
[Mon Mar 12 15:19:19 2007] [warn] (OS 64)The specified network name is no longer available. : winnt_accept: Asynchronous AcceptEx failed.
[Mon Mar 12 15:19:19 2007] [warn] (OS 64)The specified network name is no longer available. : winnt_accept: Asynchronous AcceptEx failed.
[Mon Mar 12 15:19:46 2007] [warn] (OS 121)The semaphore timeout period has expired. : winnt_accept: Asynchronous AcceptEx failed.
[client 218.59.232.222] script 'C:/Program Files/Apache Group/Apache2/htdocs/gala-auction/nshow.php' not found or unable to stat, referer: http://www.nb-ibm.com
[Mon Mar 12 15:20:08 2007] [warn] (OS 121)The semaphore timeout period has expired. : winnt_accept: Asynchronous AcceptEx failed.
[Mon Mar 12 15:20:31 2007] [warn] (OS 121)The semaphore timeout period has expired. : winnt_accept: Asynchronous AcceptEx failed.
[Mon Mar 12 15:20:31 2007] [error] [client 218.59.232.222] File does not exist: C:/Program Files/Apache Group/Apache2/htdocs/gala-auction/42, referer: http://www.nb-ibm.com
[Mon Mar 12 15:20:46 2007] [warn] (OS 64)The specified network name is no longer available. : winnt_accept: Asynchronous AcceptEx failed.
[Mon Mar 12 15:21:17 2007] [warn] (OS 121)The semaphore timeout period has expired. : winnt_accept: Asynchronous AcceptEx failed.
[client 218.6.66.250] script 'C:/Program Files/Apache Group/Apache2/htdocs/gala-auction/prx.php' not found or unable to stat
[client 74.52.144.18] script 'C:/Program Files/Apache Group/Apache2/htdocs/gala-auction/proxycheck.php' not found or unable to stat
[Mon Mar 12 15:21:17 2007] [error] [client 60.51.63.116] File does not exist: C:/Program Files/Apache Group/Apache2/htdocs/gala-auction/intl
Please help me!

re: Error Log Overflow

It looks like someone is trying to brute-force something on your site. If your server is not behind a firewall, I would recommend putting it behind one - if it is, I'd recommend dropping draffic from that user for 5 minutes or so (have a script in place that blocks traffic if so many invalid requests hit the server in such a timeperiod).

Is your server and OS updated?

re: Error Log Overflow

I did a little googling and came up with this description.