Ran into a situation where a customer had 8 cisco 2950 switches patched randomly into each other. Cleaned the configuration up where 1 master switch will feed all the other switches. Ideally this will be replaced with a 3560 gig switch.
Here is what happens to layer2 networks that keep growing as users add new switches. Normally routers would be used to break up large layer2 domains but sometimes companies forget to do this and a mess can result.
The short answer is if you are not sure, then dont. This link should help with the understanding of the different classes of spam and how they work, and what you can safely do to help reduce if not eliminate spam: