Some people are leery of using their credit cards online and for good reason. Let me share with you a method I've used for some time now with great success.
I have my main checking account with a Credit Union where I opened a second checking account so I have two Mastercard debit cards, one per account. I only use the debit card of the second account for Internet purchases.
This is how it works. I set up the second checking account so it has no overdraft protection. They will deny any charges on the account's debit card if no funds are present to cover the charge. The penalty fee for an insufficient funds rejection is $1.00, no big deal.
When I purchase something online and just before I submit my order, I log in to my credit union and transfer just enough funds to cover my purchase plus maybe $5 so there are always a few extra bucks there. There is no charge to transfer the funds from my main account to my Internet account. Then I submit the order.
The advantages are that in the event of a fraud attempt there will be very little money in that account and these attempts would be rejected by the bank. In addition, I still get all of the benefits of purchasing with a credit card, such as being able to get my money back due to defective/undelivered merchandise.
The same principle can be used when using services like Dwolla. Set up Dwolla to use the second account and only transfer money into that account when making a purchase.
Now you will be able to sleep at night, lol.