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.

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.

“The transfer speeds are satisfyingly fast for reading and writing all kinds of files, whether large HD videos or unsorted media folders,” our tester reported of this flash drive. He also liked the inclusion of the SecureAccess file encryption, although advanced features are an additional purchase. In terms of negatives, our reviewer called the plastic shell casing “flimsy and fragile” and observed that the transfer speeds are capped when the flash drive is plugged into a USB hub. Overall? Our tester was “more than satisfied with the transfer speeds, but would have appreciated a better, sturdier physical design.”

A drawback to the small size of flash drives is that they are easily misplaced or otherwise lost. This is a particular problem if they contain sensitive data (see data security). As a consequence, some manufacturers have added encryption hardware to their drives, although software encryption systems which can be used in conjunction with any mass storage medium will achieve the same result. Most drives can be attached to keychains or lanyards. The USB plug is usually retractable or fitted with a removable protective cap.

Flash drives are often measured by the rate at which they transfer data. Transfer rates may be given in megabytes per second (MB/s), megabits per second (Mbit/s), or in optical drive multipliers such as "180X" (180 times 150 KiB/s).[19] File transfer rates vary considerably among devices. Second generation flash drives have claimed to read at up to 30 MB/s and write at about half that rate, which was about 20 times faster than the theoretical transfer rate achievable by the previous model, USB 1.1, which is limited to 12 Mbit/s (1.5 MB/s) with accounted overhead.[20] The effective transfer rate of a device is significantly affected by the data access pattern.[21]

A minority of flash drives support biometric fingerprinting to confirm the user's identity. As of mid-2005,[needs update] this was an expensive alternative to standard password protection offered on many new USB flash storage devices. Most fingerprint scanning drives rely upon the host operating system to validate the fingerprint via a software driver, often restricting the drive to Microsoft Windows computers. However, there are USB drives with fingerprint scanners which use controllers that allow access to protected data without any authentication.[70]

Most USB flash drives do not include a write protection mechanism. This feature, which gradually became less common, consists of a switch on the housing of the drive itself, that prevents the host computer from writing or modifying data on the drive. For example, write protection makes a device suitable for repairing virus-contaminated host computers without the risk of infecting a USB flash drive itself. In contrast to SD cards, write protection on USB flash drives (when available) is connected to the drive circuitry, and is handled by the drive itself instead of the host (on SD cards handling of the write-protection notch is optional).

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