How do theives use a found credit card number to steal from you?

I work for a credit card processor wher I am selling new credit card machines. Here is my question, some of the older machines these merchants use print out the whole credit card number, expiration date and the customers name. I understand and wouldn't want my info on a receipt, but I am having trouble understanding how someone could take my credit card number and actually spend on it? If they go on the internet to buy something, their IP will get snatched and they would need the 3 digit code on the back of the card to finish a transaction. If they go into a store, they have to convince the cashier to handkey the card number and they have to risk being seen on camera. So how is this such a big problem? What can a theif actually do with the number?|||that depends on how they got the number. if someone gets the number from the physical card then they will go online and simply use a public computer such as the library to make the purchase. if the card is in your hand it will take all of 1 second to read the 3 digit code on the back and remeber it. some people are great with numbers and could memorize your whole care number in seconds. if they run your card through a card reader then they can simply duplicate it on blanks later. this is the prefered method these days since everywhere you go there is a self service terminal for you to swipe the card at so the thief will not even have to show the card to the cashier. as for cameras. most people who drive 45 to 50 minutes from home ot commit a fraud will never be caught even if thier face is on a camera since no one there will recognize the person. it is why so many people are doing this, because it is not as easy as you think to catch a professional thief.|||Someone can use a public computer or someone elses computer to go online. there are actually some sites that do not require the security code to complete a transaction. others know people who work in certain stores and they just run the card for them. plus there are some places that dont even ask for identification. just drive to a friendly town with extra friendly people and wala. it's very sad.