Install the plugin Exploit Scanner in wordpress, and you will be able to see the files that have been modified. Also, update all your plugins especially the timthumb.php. You may want to check /index.php , /wp-blog-header.php , /wp-login.php , wp-admin/admin-footer.php, wp-admin/admin-header.php , wp-admin/admin-header.php , wp-admin/index.php , wp-admin/menu-header.php , wp-content/index.php .
When you use the scanner plugin, you may see some highligted lines in the php files, something to do with
eval(gzinflate(base64_decode or echo(gzinflate(base64_decode. Just in case you have something like that download all those files that have been infected. I find this link useful when revealing the real codes of base64_decode lines:
Code:
http://www.tareeinternet.com/scripts/decrypt.php
Sometimes the lines are changed to
echo in the modified files, you may want to change it later in the link provided above.
Also, you may want to create a backup before modifying php files. Hope it helps you.
PS: Delete the entire lines of eval(gzinflate(base64...., and when editing use Notepad++ and change the language to PHP to actually see start and end of each lines.