Reading about the "Osama suicide" virus:

In response to this, Russian virus-makers created a trojan virus hidden in a flash movie named "BushF*Cowboy.exe". When the user runs this file it only installs the main trojan: Trojan.PSW.LdPinch, Ukrainian Antivirus Center (UAC) reports.
It looks like these flash viruses are growing in popularity. But how do they infect? Does simply browsing to a page with a flash file and allowing it to play result in the installation? If so, how? What's actually downloaded when you watch a flash file? Isn't a flash video displayed on a website a server-side execution? Or does the virus slip in while the video's loading client-side?

Just curious.