CertiGuide to Security+  9  Chapter 3:  Infrastructure Security (Domain 3.0; 20%)       9  3.2  Media            9  3.2.4  Removable Media

3.2.4.2  CD-R (Compact Disc Recordable) 1 2 3.2.4.4  Diskettes

Security Issues with Hard Drives

In contrast with the other media solutions we’ve looked at so far, a hard drive contains both media and the read/write mechanism (tapes and CD-R’s are just media … the drive contains the read/write mechanism). Because of the mechanical nature of the read/write mechanism, with heads hovering just barely above the surface of the media platters within the drive, hard drives are very sensitive to shock.

For instance, dropping a hard drive is very likely to result in a non-working drive (though some of the data may still be able to be recovered), but dropping a CD or tape is likely to be a non-event.

Again, as with tape, hard drives are magnetic media, and are sensitive to magnetic fields, thus care should be taken to keep them away from large magnets, like those in your computer speakers!

In general, the faster the drive, the more expensive, and the more heat it generates. The heat generated by a hard drive can be a concern because it can affect the reliability and lifetime of any part of the computer that is temperature-sensitive (that is, most of them). Therefore, many users who want fast hard drives opt for larger cases with better airflow, and may add extra fans to the computer case, to help cool the system.

Unlike CD-R’s, which cannot be erased once written, and tapes and diskettes which have mechanical protection against accidental overwrite (if the user wishes to employ it), most hard disks cannot be “write-protected” in hardware, so there’s always a risk that a critical piece of data will be overwritten or erased with a “format c:” or “rm *”.

Many hard drives have a MTBF (Mean Time Between Failure) rating, to allow you to compare the useful life of the drive with other similar drives since part of building a reliable system is simply choosing parts that are less likely to fail. The MTBF is usually measured in hours of operation. One interesting fact about this is that notebook drives often have a much lower MTBF than workstation or server drives. The manufacturers assume that a notebook drive will not be in use as much per day, as a typical desktop or server machine’s drive would be.

Because every day people lose data on hard drives that weren’t backed up recently (or at all), the data recovery industry is thriving. Did your disk stop working? Was there a “head crash” in which the read/write heads of the disk contact the media surface with some force, damaging it? Got errant fingers “rm –r /”?

There are plenty of “data recovery” companies, who specialize in getting the data off a disk, no matter what’s happened to it, that are ready to help you, for a price. Just search the Internet for “data recovery”. In many cases, they’ll have to totally take apart the drive, rendering it unusable, and you’ll have to replace it, but chances are that’s less important to you than getting your data back. For lesser accidents, you can purchase disk recovery software from companies such as OnTrack and Norton, which may help you do the job without enlisting expensive professionals and/or risking sending the disk two states away via a delivery service (ever see what those overnight delivery guys do with boxes when they think no one’s looking?).

3.2.4.2  CD-R (Compact Disc Recordable) 1 2 3.2.4.4  Diskettes