In the last hours I got thousands of request like this from different IP addresses:
http://ednong.de/blogs/htsrv/call_plugin.php?plugin_ID=33&method=display_captcha¶ms=a%3A1%3A%7Bs%3A6%3A%22pubkey%22%3Bs%3A32%3A%22ea3dbe247bafb77ad327f6be8f2b3c04%22%3B%7D
The key at the end will differs - so I ask myself: is this an attack for trying to log in with differences passwords/a list of passwords? What is the meaning of the plugin with the id 33? I can't find such a plugin because I see only names or the abbreviation of the plugins. And the priority of the plugins ends always on "0" (okay, some of them ends with 4, 5 or 6). But there will be no "33".
Or are these ppl trying an attack that will works on WP? And how I can stop this things?
I think this is specific to your site because WP doesn't have an
/htsrv/
folder IIRC.Edit the settings of the Captcha plugin on your system and you should see the plugin ID in the URL bar.
If you see many such calls in a row, maybe they are reloading the captcha until they find one they can decipher?