I started getting warning emails yesterday morning from my hosting company (1and1), by the end of the day they had taken my website down.
Here's part of the last email I got from them this morning:
1. Analysis of the attack
******************************************************************************
1.1 The hackers processed the attack through a security leak in your software
WordPress plugin: flash gallery
They misused at least the following modules or files of this software:
./mywebsite/wp-content/plugins/1-flash-gallery/upload.php
1.2 Via this security leak, the hackers have uploaded the following malicious
files to your webspace:
./mywebsite/wp-content/uploads/fgallery/20110916171543.php
./mywebsite/wp-content/uploads/fgallery/20110923084726.php
./mywebsite/wp-content/uploads/fgallery/sm3wt4.php
./mywebsite/wp-content/uploads/fgallery/htaccess
1.3 In order to impede further attacks, we have disabled these files. Please
note that part of your websites may be impaired.
1.4 We have unlocked your 1&1 webspace. Please understand that this temporary
lock was necessary to protect your security.
I did have this plugin installed until this morning, but it was not activated.
In a previous email I got from 1and1, they said that a massive number of emails were being sent from my webspace.
I hope this helps in any way.