Let's assume I take classess online. How do the teacher know it is me who does the homework and stuff? I don't want to cheat but I was wondering if they have any tools to determine who is posing messages, who really does tests online etc.?

I suspect they have the tools to do it. Your ISP's IP for example. Besides, it wouldn't take much sense to pay for classes and have someone else do them, would it? It's not like getting help with writing one or two essays; online classes usually take a few weeks to complete so if you miss it, you'll most likely have no knowledge about the subject. Finally, I think online classes are great for those who really need them (working students for example) so even talking about the idea that someone else could do your online coursework is not very smart. It's just my opinion.

Beatrice

Yeah, I guess you're right. I just wanted to make sure my online friends know it too ;-).

I know many people who take online classes. I don't think any of them is cheating. As noted by beatrice, it wouldn't make sense at all.