Also they were quite common when the owner had reloaded the OS. I'll explain why the Sasser and the other worms get in during the reload.

Most restore CDs are XP or even XP SP1. These versions have no protection from modern worms and the owner forgets to install a firewall before connecting to the internet.

So to fix this we reload the OS, then add the firewall to recover if it's a fresh install. No need to repair the damage since we don't want any chance of the newer rootkits and more. Besides it takes more hours (120 per hour!) so we take the cheap route.

Look up SASSER on to see how to deal with it.