The only little white worms I know of in home aquaria are Planaria. Planaria are flatworms, related to flukes and tapeworms. They typically aren't harmful to fish, but they will feast on eggs from fish, possibly from snails too.
Even though Planaria do not harm fish, they are an indicator that the aquarium has a problem. They require a food source, which means there must be excess food wastes in the tank to support them.
Biggest cause of this is...well, lack of cleaning(you said you don't clean the back glass, I'm wondering if you miss other things in the back area like the substrate...), over-feeding too.
Best cure is a good clean of your substrate and scrub that back window! Try to suck out the worms you see first though, and then throughly clean out your substrate....this may not get them all, but you can manage it by paying closer attention to your cleaning and don't skip areas(of course you don't want to do all the areas all at once as it can shock the beneficial bacteria in your tank...but should be alright if you don't tamper with the filter. However this means they may be in your filter too).
There might be better ways to get rid of them, the only one I know of is to start cleaning properly and get rid of them. Hopefully others can give you ideas. Most of these critters hate salt, but I don't know about plenaria.
