I was foolish enough to give personal information to a scam lottery set-up. I sent them a scanned copy of my passport (without signature), address, telephone number, occupation. Since I had also paid them a small amount online using a prepaid ecard, I wonder if they might have access to other personal info.
The issue here is identity theft. Have I already left myself open to this? What could be done with the info I parted with? Is there anything I could or should do at this point (shutting the stable door ...............................)?


First thing I would do is to contact my credit card company and bank. They deal with this sort of stuff daily.
If you were in the US you would be well advised to check your credit reports frequently. I'm not sure how credit reporting works down under.
Perhaps there is a government agency that maintains an advisory web site?
If I was in your situation I would contact the passport office and get a new one, obviously with a new number. Contact your "ecard" company and ask for a new card and number. Yes it's inconvenient, but will give you piece of mind.
Also, as Bob mentioned, check your credit reports and look for inquiries. Here in the States we can put a "fraud alert" on our credit reports. With the alert, all new applications for credit will require a call to your home phone, and a bunch of personal questions that only you should know.