IT Media Security Basics

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In the previous chapter we began looking at the security as it relates to the various elements that comprise a typical IT infrastructure. In this chapter we will look at media security in terms of both cable media and storage media.




Cable Media

Cable media is what constitutes the Physical layer of the OSI model and provides the actual connection between devices on a network. The four primary methods for connecting devices at the physical layer are coaxial cable, twisted pair cable, fibre optics and wireless. Since wireless connectivity doesn't involve any physical cable media we will look at the first three types of media in this chapter.

Coax Cable

Coax cable came to prominence in network installations during the 1980s and was part of the first specification for Ethernet. Coaxial cable will be familiar to those with cable or satellite television connections. It is heavily shielded and as such is much less susceptible to interference than standard twisted pair cabling.

Two types of coax are available. Thinnet, also known as 10Base2 has a communication speed of 10Mbps, is limited in length to 185 meters per network segment and uses BNC style connectors. Each end of a 10Base10 network must be terminated by a special connector called a terminator.

Thicknet, also known as 10Base5 has communication speed of 10Mbps, a maximum segment length of 500 meters and uses attachment unit interfaces and vampire clips to connect devices to the network.

Coax cable has no inherent security. The linear nature of the coax network topology is such that the cable may be pierced or spliced at any point and a new device added to the network.


Shielded and Unshielded Twisted Pair Cable (UTP/STP)

Almost all coax cable has now been replaced with faster twisted pair cable. Twisted pair cable uses pairs of twisted wires (as used by phone lines). The grouping together of multiple twisted pairs limits cross talk and interference enabling greater transmission speeds to be achieved.

Shielded twisted pair cable has a foil shield around each pair of wires in the cable to further minimize electromagnetic interference. Unshielded twisted pair, on the other hand, relies solely on the pair twisting to limit interference and cross-talk.

Twisted pair cabling is categorized by transmission level as follows:

  • Category 3 (Cat 3) - Suitable for voice and data speeds up to 10Mbps
  • Category 5 (Cat 5) - Suitable for 100Mbs transmission (Fast Ethernet)
  • Category 6 (Cat 6) - Suitable for Gigabit Ethernet

Twisted pair cables use RF-45 connectors and are harder to tap into than coax cable. The biggest risk for twisted pair cable is the ease with which additional devices can be connected to spare ports on hubs, routers and switches.

Fiber Optic Cable

Fiber optic cable involves the firing of laser light down thin strands of glass providing vast levels of bandwidth up to terabits per second. Fiber is primarily used to provide the backbone for large networks and the internet and is very rarely run to desks in the same way twisted pair is. One of the reasons for this is the cost. Fiber optic cable is so expensive that it is only economical to deploy it when the provided level of bandwidth is truly needed.

Connecting fiber optic is also an extremely difficult and specialized skill and splicing cable is close to impossible.

Fiber cable is extremely secure. It does not radiate any signal and is impossible to tap into without highly specialized equipment and training.

Removable Storage Media

The days of the floppy disk drive that could only hold a little over 1MB of data are long gone. Today we are faced with a fast array of storage options capable of holding massive quantities of data including tape, removable disk drives (magnetic media), CD-ROM, DVD (optical media) and even flash cards (electronic media). In this section we will look at these forms of removable media in detail.

Hard Drives

Not so long ago the concept of a disk drive that was smaller than a packet of cigarettes was unthinkable. The reality of today is that such a disk drive would be considered large by some standards. Today many gigabytes of data can be stored on a portable disk drive.

Diskettes

Once the sole method for transferring data between computers (a concept often known as sneaker net), and with a storage capacity of just 1.44Mb, diskettes are now all but obsolete.

Tape Storage

Tapes could actually be considered the first form of removable storage media. Watch an old 1960s Sci-Fi movie and the chances are that the computer will be large refrigerator sized boxes with large tape spools spinning on the front. Tapes are primarily used for backing up data. Disadvantages of tapes are the serial nature in which data is stored (making them useless for random access of specific files) and their relatively slow speed compared to other storage media. A number of tape formats are available today including Digital Audio Tape (DAT), Digital Linear Tape (DLT) and good old fashioned quarter inch tape.

The primary security risk inherent in tapes is storage. Steps must be taken to ensure that all tapes (both onsite and offsite are stored securely so that they do not fall into unauthorized hands.

CD-R/DVD

The data version of the CD music disk is capable of holding 650Mb of data. The DVD standard stores as much as 4Gb of data and newer high definition DVD disks such as Blu-ray hold even greater amounts of data.

These discs work using small marks burned onto the disk by a laser, each mark representing a binary 1 or 0. The first type of CD was read only and could only be manufactured using specialized technology. This was followed by CD-R which enabled users to burn their own disks using special CD drives. Once the disk was created, however, it was read-only and could not be re-written. Subsequently, CD-RW technology enabled users to erase and re-write to disks many times.

Electronic Media

The most recent development in the storage media field involves memory based cards and disk drives. These devices contain banks of static memory (by static we mean that data remains when power is removed). Initially popular in cameras, PDAs and music players (typically using Smart Cards and Flash Cards), this technology is now moving rapidly into disk technology with a wide range of high capacity, solid state hard disks now available. The advantages of this technology include lower power consumption (no need for the motor and spinning plates of a conventional disk drive) and durability (none of the fragile moving parts to get damaged when dropped).

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IT Infrastructure SecurityNetwork Security Topologies