Information leakage from corporate computer systems is a big social problem in terms of the protection of corporate assets and customers' privacy. Digital assets are usually brought out of companies with the portable devices such as USB memory sticks, PDAs, and laptop PCs. This paper proposes a scheme that protects the information leakage via portable devices so that the access to sensitive files on a storage device attached to a computing device is allowed only when the latter is located inside the company and is connected to the company's network. To detect this, we use the IP addresses of the company and the computing device, but also a challenge-response authentication protocol to prevent such attacks that simulate the company's system to camouflage the computing device's location.