Bots trying to find phpMyAdmin

[SEOPTI]

Is it a problem because my server is issuing 301 instead of 403?

Will this line help?
SetEnvIfNoCase User-Agent "phpmyadmin" banned

163.xx- - [05/Sep/2007:00:16:49 +0200] "GET /web/main.php HTTP/1.0" 301 329 "-" "-"
163.xx- - [05/Sep/2007:00:16:50 +0200] "GET /PMA/main.php HTTP/1.0" 301 329 "-" "-"
163.xx - - [05/Sep/2007:00:16:50 +0200] "GET /dbadmin/main.php HTTP/1.0" 301 333 "-" "-"
163.xx - - [05/Sep/2007:00:16:51 +0200] "GET /admin/phpmyadmin/main.php HTTP/1.0" 301 342 "-" "-"
163.xx- - [05/Sep/2007:00:16:51 +0200] "GET /admin/phpMyAdmin/main.php HTTP/1.0" 301 342 "-" "-"
163.xx- - [05/Sep/2007:00:16:55 +0200] "GET /mysql/phpmyadmin/main.php HTTP/1.0" 301 342 "-" "-"
163.xx- - [05/Sep/2007:00:16:56 +0200] "GET /mysql/phpMyAdmin/main.php HTTP/1.0" 301 342 "-" "-"
163.xx- - [05/Sep/2007:00:16:56 +0200] "GET /sql/phpmyadmin/main.php HTTP/1.0" 301 340 "-" "-"
163.xx- - [05/Sep/2007:00:16:57 +0200] "GET /sql/phpMyAdmin/main.php HTTP/1.0" 301 340 "-" "-"
163.xx- - [05/Sep/2007:00:16:57 +0200] "GET /PMA/read_dump.phpmain.php HTTP/1.0" 301 342 "-" "-"
163.xx- - [05/Sep/2007:00:16:58 +0200] "GET /mysql/read_dump.phpmain.php HTTP/1.0" 301 344 "-" "-"

[volatilegx]

Will this line help?
SetEnvIfNoCase User-Agent "phpmyadmin" banned

No, because the user-agent string is blank.

[keyplyr]

SEOPTI, I use mod_rewrite to block hits that do not show a UA, while still allowing HEAD requests which often won't show one:

RewriteEngine On
RewriteCond %{HTTP_USER_AGENT} ^-?$
RewriteCond %{REQUEST_METHOD} !^HEAD$
RewriteRule .* - [F]

However, I suggest you monitor logs closely as many friendly hits also do not show a UA. So you will need allow some IP addresses, example: Google mobile, M$, Yahoo, etc.

[SEOPTI]

keyplyr, Thanks!

[incrediBILL]

Just blocking that won't stop them as that's a calling card of a botnet probing your site.

If they actually find something vulnerable you need to block any access attempt with "=http:" in the query string to stop the actual script injection.