There are a variety of tools available that are able to block or monitor USB ports, therefore limiting/preventing the ability to for users to take data out of the company via USB drives.
But what if your staff do need access to USB drives, e.g to take presentations from the servers to their laptops, or to move large CAD or graphic files around the office, or between offices. USB drives have their value and blocking them all together is often not the solution.
Technology nowadays allows users to bind USB drives to particular machines, i.e only those USB drives will work, and not others. In addition to this they can also ensure that the USB drive are encrypted. So when a USB drive is lost, it does not mean that the data is lost, just a £20 device.