Some manufacturers deploy physical authentication tokens in the form of a flash drive. These are used to control access to a sensitive system by containing encryption keys or, more commonly, communicating with security software on the target machine. The system is designed so the target machine will not operate except when the flash drive device is plugged into it. Some of these "PC lock" devices also function as normal flash drives when plugged into other machines.
Flash memory combines a number of older technologies, with lower cost, lower power consumption and small size made possible by advances in microprocessor technology. The memory storage was based on earlier EPROM and EEPROM technologies. These had limited capacity, were slow for both reading and writing, required complex high-voltage drive circuitry, and could be re-written only after erasing the entire contents of the chip.
Most USB-based flash technology integrates a printed circuit board with a metal tip, which is simply soldered on. As a result, the stress point is where the two pieces join. The quality control of some manufacturers does not ensure a proper solder temperature, further weakening the stress point.[77][78] Since many flash drives stick out from computers, they are likely to be bumped repeatedly and may break at the stress point. Most of the time, a break at the stress point tears the joint from the printed circuit board and results in permanent damage. However, some manufacturers produce discreet flash drives that do not stick out, and others use a solid metal uni-body that has no easily discernible stress point. SD cards serve as a good alternative to USB drives since they can be inserted flush.
USB flash drives usually specify their read and write speeds in megabytes per second (MB/s); read speed is usually faster. These speeds are for optimal conditions; real-world speeds are usually slower. In particular, circumstances that often lead to speeds much lower than advertised are transfer (particularly writing) of many small files rather than a few very large ones, and mixed reading and writing to the same device.
Flash drives may present a significant security challenge for some organizations. Their small size and ease of use allows unsupervised visitors or employees to store and smuggle out confidential data with little chance of detection. Both corporate and public computers are vulnerable to attackers connecting a flash drive to a free USB port and using malicious software such as keyboard loggers or packet sniffers.
It's never been easier to take all the files, data or media you want with you wherever you go. Generally about the size of a stick of gum, a USB flash drive lets you store any file from your computer so you can save it, transport it, and load it onto another computer in seconds. You simply plug the flash drive into your USB port and drag any files you want onto its icon on your desktop. Best of all, flash drives have no internal moving parts, so they're very resistant to breaking by being bumped or dropped.
