Not saying you should buy this software.  But if you are worried about someone ripping
off your credit card number on a particular purchase, what you can do is buy a Visa
gift card for that amount.  It works just like a regular credit card, but is only worth
a specific amount of money.  Then if someone tries to charge more to it, it won't
work because the limit has already been exceded.  So if you do get ripped off,
it is only for the amount of money the card is worth.  And it can't be reloaded,
so when you are done with the card, you just throw it away.