• Choose a category
• All
• Classic-Fiction

By Root 3179 0

STP cabling isn’t as secure as coax because it can be easily tapped into, and it’s used primarily for internal wiring. It’s more difficult to splice into a twisted-pair cable, but three-way breakout boxes are easy to build or buy. The common networks that use UTP are 10Base-T, 100Base-T, and 1000Base-T. These networks use hubs for distribution, and hubs allow sniffers to be easily connected. Many modern networks include switches, and network monitoring doesn’t work properly through a switch unless the switch is configured to allow it. Remember that each circuit through a switch is dedicated when switched and won’t be seen on the other ports. Figure 3.24 illustrates a hub in a 10Base-T network and a sniffer attached to the hub. The sniffer in this situation is a portable PC with a NIC for the network protocol.

Fiber Optic

Fiber-optic technology takes network bandwidth to new levels of performance. Telecommunications and data communication providers worldwide have laid fiber cables extensively. At one point, the industry claimed that fiber would surpass wire as the preferred method of making network connections. Fiber optics and its assembly continue to be very expensive when compared to wire, and this technology isn’t common on the desktop.

FIGURE 3.24 10Base-T network with a sniffer attached at the hub

Because fiber-optic cabling uses light in place of an electrical signal, it’s less likely than other implementations to be affected by interference problems.

Fiber, as a media, is relatively secure because it can’t be tapped easily. Fiber’s greatest security weakness is at the connections to the fiber-optic transceivers. Passive connections can be made at the connections, and signals can be tapped from there. The other common security issue associated with fiber optics is that fiber connections are usually bridged to wire connections. Figure 3.25 shows how a fiber connection to a transceiver can be tapped. This type of splitter requires a signal regenerator for the split to function, and it can be easily detected.

FIGURE 3.25 An inline fiber splitter

Infrared

Infrared (IR) uses a type of radiation for communications. This infrared radiation allows a point-to-point connection to be made between two IR transceiver-equipped devices. IR connections tend to be slow and are used for limited amounts of data. Many newer laptop PCs, PDAs, and portable printers now come equipped with IR devices for wireless communications.

IR is line of sight; it isn’t secure and can be easily intercepted. But the interception device must be either in position between the two connections or in an area where a reflection has occurred. (IR can be bounced off windows and mirrors, as can other radiation.)

Radio Frequencies

Radio frequency (RF) communications have had an interesting love/hate relationship with data communication. Early data communications systems, such as teletypes, used extensive networks of high-powered shortwave transmitters to send information and data. Most of the early news feeds were broadcast on shortwave frequencies and received around the world by news offices. These connections were also used for early facsimile transmission of weather maps and other graphically oriented images. The transmitters were very expensive, and large numbers of personnel were required to manage and maintain them. Telephone connections largely replaced this means of communications, but teleprinters are still in use today.

RF transmissions use antennas to send signals across the airwaves. These signals can be easily intercepted. Anyone can connect a shortwave receiver to the sound card of a PC to intercept, receive, and record shortwave and higher-frequency transmissions. Figure 3.26 illustrates a shortwave transmission between two ground sites used for text transmission. This is an active pastime—tens of thousands of hobbyists worldwide are eavesdropping.

Microwave Systems

Microwaves use the RF spectrum, but they have some interesting characteristics and capabilities. The microwave frequency spectrum