One of our blogging friends were infected with this trojan horse recently. In short, it suggests that the blogosphere continues to be the wild wild west. In this particular hack, the trojan is planted via a vunerability in older versions of WordPress.
As Bloggers engage via ping services & XML-RPC, they start pinging strangers on the internet. Such strangers could be running innocent-looking blogs. They could be hackers. So a hacker who previously didn’t know of your existance now does a quick vunerability check on you.
The point here is:
1) Upgrade WordPress frequently to the second last stable version (not the last one)
2) Make frequent backups and store them off-site.
3) If you are an active blogger with an older version of WordPress, there is a good chance that you might be infected.