Security Risks

Trading convenience for security is a fact of life in the computer world. Anytime you make it easier to share your data with anyone, it can easly become available to everyone. External hard drives pose security risks. Portable hard drives and flash drives pose much bigger security risks.
If you're using a desktop external unit, you need to make sure you secure it. You can buy external drives that have degrees of data protection, including encryption. Also make sure your main desktop or laptop unit is password protected against unauthorized entry. Portable drives are much more of a potential problem. You can buy secure portable drives, with password-protected or even biometrically protected partitions. This can be key if you're carrying anything you wouldn't want the world to see if you happened to lose your flash drive. Remember, they are pretty small.