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Cable is the medium through which information usually moves from one network device to another. There are several types of cable which are commonly used with LANs. In some cases, a network will utilize only one type of cable, other networks will use a variety of cable types. The type of cable chosen for a network is related to the network's topology, protocol, and size. Understanding the characteristics of different types of cable and how they relate to other aspects of a network is necessary for the development of a successful network.

The following sections discuss the types of cables used in networks and other related topics.

* Unshielded Twisted Pair (UTP) Cable
* Shielded Twisted Pair (STP) Cable
* Coaxial Cable
* Fiber Optic Cable
* Wireless LANs
* Cable Installation Guides



Unshielded Twisted Pair (UTP) Cable

Twisted pair cabling comes in two varieties: shielded and unshielded. Unshielded twisted pair (UTP) is the most popular and is generally the best option for school networks.



The quality of UTP may vary from telephone-grade wire to extremely high-speed cable. The cable has four pairs of wires inside the jacket. Each pair is twisted with a different number of twists per inch to help eliminate interference from adjacent pairs and other electrical devices. The tighter the twisting, the higher the supported transmission rate and the greater the cost per foot. The EIA/TIA (Electronic Industry Association/Telecommunication Industry Association) has established standards of UTP and rated five categories of wire.
Categories of Unshielded Twisted Pair
Type Use
Category 1 Voice Only (Telephone Wire)
Category 2 Data to 4 Mbps (LocalTalk)
Category 3 Data to 10 Mbps (Ethernet)
Category 4 Data to 20 Mbps (16 Mbps Token Ring)
Category 5 Data to 100 Mbps (Fast Ethernet)

Buy the best cable you can afford; most schools purchase Category 3 or Category 5. If you are designing a 10 Mbps Ethernet network and are considering the cost savings of buying Category 3 wire instead of Category 5, remember that the Category 5 cable will provide more "room to grow" as transmission technologies increase. Both Category 3 and Category 5 UTP have a maximum segment length of 100 meters. In Florida, Category 5 cable is required for retrofit grants. 10BaseT refers to the specifications for unshielded twisted pair cable (Category 3, 4, or 5) carrying Ethernet signals. Category 6 is relatively new and is used for gigabit connections.
Unshielded Twisted Pair Connector

The standard connector for unshielded twisted pair cabling is an RJ-45 connector. This is a plastic connector that looks like a large telephone-style connector. A slot allows the RJ-45 to be inserted only one way. RJ stands for Registered Jack, implying that the connector follows a standard borrowed from the telephone industry. This standard designates which wire goes with each pin inside the connector.



Shielded Twisted Pair (STP) Cable

A disadvantage of UTP is that it may be susceptible to radio and electrical frequency interference. Shielded twisted pair (STP) is suitable for environments with electrical interference; however, the extra shielding can make the cables quite bulky. Shielded twisted pair is often used on networks using Token Ring topology.
Coaxial Cable

Coaxial cabling has a single copper conductor at its center. A plastic layer provides insulation between the center conductor and a braided metal shield. The metal shield helps to block any outside interference from fluorescent lights, motors, and other computers.



Although coaxial cabling is difficult to install, it is highly resistant to signal interference. In addition, it can support greater cable lengths between network devices than twisted pair cable. The two types of coaxial cabling are thick coaxial and thin coaxial.

Thin coaxial cable is also referred to as thinnet. 10Base2 refers to the specifications for thin coaxial cable carrying Ethernet signals. The 2 refers to the approximate maximum segment length being 200 meters. In actual fact the maximum segment length is 185 meters. Thin coaxial cable is popular in school networks, especially linear bus networks.

Thick coaxial cable is also referred to as thicknet. 10Base5 refers to the specifications for thick coaxial cable carrying Ethernet signals. The 5 refers to the maximum segment length being 500 meters. Thick coaxial cable has an extra protective plastic cover that helps keep moisture away from the center conductor. This makes thick coaxial a great choice when running longer lengths in a linear bus network. One disadvantage of thick coaxial is that it does not bend easily and is difficult to install.
Coaxial Cable Connectors

The most common type of connector used with coaxial cables is the Bayone-Neill-Concelman (BNC) connector. Different types of adapters are available for BNC connectors, including a T-connector, barrel connector, and terminator. Connectors on the cable are the weakest points in any network. To help avoid problems with your network, always use the BNC connectors that crimp, rather than screw, onto the cable.



Fiber Optic Cable

Fiber optic cabling consists of a center glass core surrounded by several layers of protective materials. It transmits light rather than electronic signals eliminating the problem of electrical interference. This makes it ideal for certain environments that contain a large amount of electrical interference. It has also made it the standard for connecting networks between buildings, due to its immunity to the effects of moisture and lighting.

Fiber optic cable has the ability to transmit signals over much longer distances than coaxial and twisted pair. It also has the capability to carry information at vastly greater speeds. This capacity broadens communication possibilities to include services such as video conferencing and interactive services. The cost of fiber optic cabling is comparable to copper cabling; however, it is more difficult to install and modify. 10BaseF refers to the specifications for fiber optic cable carrying Ethernet signals.



Facts about fiber optic cables:

* Outer insulating jacket is made of Teflon or PVC.
* Kevlar fiber helps to strengthen the cable and prevent breakage.
* A plastic coating is used to cushion the fiber center.
* Center (core) is made of glass or plastic fibers.

Fiber Optic Connector

The most common connector used with fiber optic cable is an ST connector. It is barrel shaped, similar to a BNC connector. A newer connector, the SC, is becoming more popular. It has a squared face and is easier to connect in a confined space.
Ethernet Cable Summary
Specification Cable Type Maximum length
10BaseT Unshielded Twisted Pair 100 meters
10Base2 Thin Coaxial 185 meters
10Base5 Thick Coaxial 500 meters
10BaseF Fiber Optic 2000 meters
100BaseT Unshielded Twisted Pair 100 meters
100BaseTX Unshielded Twisted Pair 220 meters

Wireless LANs

Not all networks are connected with cabling; some networks are wireless. Wireless LANs use high frequency radio signals, infrared light beams, or lasers to communicate between the workstations and the file server or hubs. Each workstation and file server on a wireless network has some sort of transceiver/antenna to send and receive the data. Information is relayed between transceivers as if they were physically connected. For longer distance, wireless communications can also take place through cellular telephone technology, microwave transmission, or by satellite.

Wireless networks are great for allowing laptop computers or remote computers to connect to the LAN. Wireless networks are also beneficial in older buildings where it may be difficult or impossible to install cables.

The two most common types of infrared communications used in schools are line-of-sight and scattered broadcast. Line-of-sight communication means that there must be an unblocked direct line between the workstation and the transceiver. If a person walks within the line-of-sight while there is a transmission, the information would need to be sent again. This kind of obstruction can slow down the wireless network.

Scattered infrared communication is a broadcast of infrared transmissions sent out in multiple directions that bounces off walls and ceilings until it eventually hits the receiver. Networking communications with laser are virtually the same as line-of-sight infrared networks.

Wireless LANs have several disadvantages. They provide poor security, and are susceptible to interference from lights and electronic devices. They are also slower than LANs using cabling.
Installing Cable - Some Guidelines

When running cable, it is best to follow a few simple rules:

* Always use more cable than you need. Leave plenty of slack.
* Test every part of a network as you install it. Even if it is brand new, it may have problems that will be difficult to isolate later.
* Stay at least 3 feet away from fluorescent light boxes and other sources of electrical interference.
* If it is necessary to run cable across the floor, cover the cable with cable protectors.
* Label both ends of each cable.
* Use cable ties (not tape) to keep cables in the same location together.

How many times have you downloaded an app that could supposedly solve all of your computer problems absolutely free of cost? Now ask yourself how many times that app actually did what it was supposed to, or better yet how many times that app was actually free? More often than not your answer is going to be zero.

Unfortunately for all of us, most software providers use gimmicks to sucker consumers in to purchasing their enterprise security apps: Sure, they'll keep your computer virus free for 30 days, but after that you'll need a subscription. Otherwise they'll just scan your registry for bugs but won't fix them for you. Frankly, we're tired of that.

To keep your computer safe (and save some cash while doing it) we've assembled a list of 103 free security apps for Mac, Windows and Linux. By the end of the article you should have enough resources to secure even the most naïve system, for free!

Spyware
The biggest enemy of the internet user today is spyware. How many computers have you seen rendered useless because of 20 IE toolbars and 15 apps running in the background? To keep your computer running at full performance you need a spyware scanner.

1. Ad-Aware SE Personal [Windows] – Popular, comprehensive spyware removal tool. Maintains a large blacklisted spyware database and identifies malicious program code for the best possible detection.
2. Spyware Terminator [Windows] – Monitors all running processes in real time and determines their integrity. If spyware is found, moves the files to a quarantined section of the hard drive or deletes the files on system start-up.
3. Spybot - Search & Destory [Windows] – Uses deep scanning techniques to cleanse your system of the most obscure forms of spyware. Allows you to blacklist certain types of spyware in order to prevent it from showing up on your system again.
4. Winpooch [Windows] – Intercepts programs in real time via API hooking; determines the integrity of the program and shuts out spyware and Trojan horses from writing in a system directory, connecting to the internet, or doing anything harmful to the computer.
5. SpywareBlaster [Windows] – Prevents the installation of ActiveX based spyware, blocks tracking cookies and restricts the actions of malicious websites.
6. Bazooka Adware and Spyware Scanner [Windows] – Scans your computer for the more popular types of spyware usually found bundled with software packages and removes the malicious content.
7. Windows Defender [Windows] – Microsoft's solution for protecting your computer from spyware and popups.
8. MalWhere [Windows] – Displays detailed information about the processes running on your computer including those that run at start up. Investigates suspicious processes and let's you know when malicious code is being executed. Does not require a spyware definition updating.
9. Trend Micro Anti-Spyware for the Web [Web: Windows] – Online based spyware detection and removal tookit. Perfect solution for non tech savvy users.
10. Zebra scanner [Mac] – Scans files for hidden agendas (e.g. a trojan disguised as an MP3 or image.) Notifies the user of the scanned files integrity. Does not contain a method for disinfecting the computer.

Antivirus
Perhaps the ultimate definition of computer security is the effectiveness of your antivirus. Antivirus software keeps the most problematic forms of malware from corrupting your computer.

1. McAfee AVERT Stinger [Windows] – Tool used to remove specific current popular viruses and worms. Make sure to download the version of Stinger pertaining to the virus found on your machine.
2. PC Tools AntiVirus [Windows] – Comprehensive virus scanning suite offering protection from malicious internet software, email attachments and boot sector viruses. Includes real time virus scanning.
3. Clam AntiVirus [Linux] – Extremely popular antivirus solution for UNIX based machines. Includes real time virus scanning and a virus definition database updated multiple times per day.
4. AVScan [Linux] – A front-end for Clam AntiVirus.
5. ClamXav [Mac] – Uses ClamAV engine to scan files for viruses.
6. AVG Anti-Virus [Windows, Linux] – Effective virus scanning suite. Requires regular virus definition updates.
7. Avast Home Edition [Windows, Linux] – Complete antivirus suite including real time scanning, email protection, internet traffic filtering, a firewall and more.
8. Housecall [Web: Windows, Linux, Mac] – Web based scanner that detects and removes viruses, worms, trojans and spyware. Also points out system vulnerabilities and offers advice on obtaining security patches.
9. Symantec Security Check [Web] – Simple antivirus solution that searches your computer for various forms of malware and deletes them. Offers a secondary scan to measure the vulnerability of your computer.

Rootkit
Rootkits are about the nastiest forms of malware around. To keep your computer (and your privacy) safe, you'll need an app to scan for rootkits.

1. Sophos Anti-Rootkit [Windows] – Removes complex rootkits and various types of malware running in a hidden state from personal and network computers.
2. Rootkit Hunter [Mac] – Searches for popular UNIX and Mac rootkits and removes them.
3. chkrootkit [Linux] – The definitive solution for finding and removing rootkits from Linux machines.

Firewall
A well regarded firewall with a strict rule set is the first line of defense against intruders. Keep hackers from sneaking malware onto your system in the first place with these freebie firewall solutions.

1. ZoneAlarm [Windows] – Popular, comprehensive firewall suite including a highly customizable rule set and a very effective warning system letting you know when your computer is at risk. Be sure to select "I only want basic ZoneAlarm protection" from the download screen (otherwise you'll end up with a trial version.)
2. VisualZone [Windows] – Analyzes ZoneAlarm information including intrusion types and methods of entry. Allows you to gain a clear view of your system's vulnerabilities.
3. PC Tools Firewall Plus [Windows] – User friendly firewall that monitors the applications connecting to the network. Uses a simple rule set to prevent malware from infecting your computer.
4. Firestarter [Linux] – Real time firewall that monitors all of the open ports and active network connections on your computer. Allows you to specify a very strict rule set.
5. Firewall Builder [Linux] – Useful tool for assembling a firewall rule set or policy for popular UNIX based firewalls including iptables, ipfilter, etc.
6. TuxGuardian [Linux] – Verifies the integrity of applications trying to gain access to the network. Useful for preventing viruses, trojans, spyware, etc. from spreading throughout the network.
7. HardWall Firewall [Linux] – Iptables based script that performs detailed packet inspection and filtering to keep your computer free from malicious traffic.
8. BullDog [Linux] – Complex firewall for advanced users.
9. PeerGuardian [Windows, Linux, Mac] – Blocks IPs from accessing your network. Especially useful for protecting your privacy when using peer to peer software.

Network
With an insecure network not only will you be vulnerable to the perils of the internet, everyone connected to your network will too. Meaning instead of having one computer down due to a nasty virus, you could have hundreds. These freebie apps will help you manage the challenge of keeping your network safe.

1. SoftPerfect Network Scanner [Windows] – Displays information about the configuration of your network.
2. SecureRDP [Windows] – Allows you to monitor and reject the incoming RDP connections to your server.
3. Colasoft Packet Player [Windows] – Capture packets and trace their route through your network. Extremely useful for finding bottlenecks and vulnerable points.
4. DomainScan Light [Windows] – Monitor open ports, connected devices, changes made to your network.
5. SmoothWall [Linux] – Firewall, IDS and VPN system for home users and networks.
6. Nagios [Linux] – Comprehensive web based tool equipped with virtually every imaginable feature for knowing exactly what's going on in your network.
7. nLive Core [Linux] – Monitors the traffic that traverses your network via packet inspection and filtering.
8. Network Mapper [Windows, Linux, Mac] – Uses packets passing through the network to find out what hosts are available, what services they're offering, what operating system they're running and what type of packet filtration/firewall they're using.
9. Wireshark [Windows, Linux, Mac] – Powerful tool for capturing network protocol data for analysis. Contains more than 25 methods for reading packets making it useful for a wide array of networks.
10. Nessus [Windows, Linux, Mac] – Industry leading open source network vulnerability scanner. Highly scalable and very thorough.
11. dSniff Control [Mac] – Tool used to test the security of your network. Tries various sniffing and spoofing exploits to gain information about your network.
12. Flame [Mac] – Simple tool used to breakdown the status and events taking place in your network.
13. Server Admin Tools [Mac] – Apple's solution for securing and monitoring a network.

Temporary Files
What websites have you been visiting? What's that, too embarrassed to say? Don't worry, we've got you covered. Simply use one of these apps to delete all of your temporary files and clean up the trail you left behind.

1. HijackThis [Windows] – Scans your computers browser, registry and operating system settings to generate a report of the state of your computer. Allows you to select which software and settings to delete.
2. Zappit System Cleaner [Windows] – Cleans up the footprints you leave when using the computer including: temporary files, recent documents, search and run commands, auto complete internet forms and history and more.
3. CCleaner [Windows] – A system optimization and privacy tool that cleans up the registry, temporary files, cookies, web history and cache and more.
4. WinXPatch [Windows] – A tool used to perform several security upgrades to the default installation and registry.
5. Advanced WindowsCare v2 Personal [Windows] – Cleans up temporary files and the registry to maximize your privacy. Also doubles as a spyware remover.
6. EasyCleaner [Windows] – A comprehensive tool for cleaning up the registry and deleting your footprints on the computer. Includes software to manage programs at start up and free up disk space.
7. CleanCache [Windows] – Deletes the temporary files you leave behind when you surf the internet.
8. xpy [Windows] – Improves the general security of your system by reconfiguring some of the default computer settings.
9. Cookie Eraser [Windows] – A tool to help you identify and erase the unnecessary cookies on your computer.
10. Yet Another System Utility [Mac] – Clears the cache, browser history and other areas where you might have left a footprint while using the computer.

Wireless
Securing your WiFi network is easier than it sounds. By taking a few extra minutes to install a few of the following apps, you'll have your WiFi network on lockdown in no time.

1. Kismet [Linux, Mac] – Very popular wireless network detector, sniffer, and IDS.
2. AirSnare [Windows] – Wireless IDS that alerts you when an unfriendly MAC address is trying to access your network.
3. myWIFIzone [Windows] – Acts as a gateway to block people from accessing your WiFi connection without receiving permission from you first.
4. iOpus Private Internet Gateway [Windows] – Creates a secure tunnel that encrypts your inbound and outbound WiFi communications. Protects your privacy on public networks.
5. LucidLink WiFi Client [Windows] – Simplifies the process of securely connecting to a WiFi network, and warns you when you're connecting to an insecure network.
6. AirTrafficControl [Mac] – Monitors your WiFi connection for quality and security.

Encryption
Encryption is a must for the most sensitive types of data. After all, we all know what happens when a password or credit card number winds up in the wrong persons hands. That's why we recommend you check out a few of the following encryption apps.

1. Pastor [Mac] – Simple tool used to securely store all of your usernames and passwords.
2. Access Manager [Windows] – Stores all of your sensitive passwords and personal information into one secure file.
3. RememberMe [Windows] – Stores your usernames and passwords in an 128-bit AES encrypted file.
4. Kruptos 2 [Windows] – Integrates into windows right click menus to encrypt and archives files easily.
5. Crypt4Free [Windows] – Uses Blowfish and DESX encryption to protect your files and create encrypted messages for instant messaging and email clients.
6. PicSecret [Web, Mac] – Neat feature that allows you to send encrypted messages disguised as ordinary pictures.
7. GNU Privacy Guard [Windows, Linux, Mac] – A command line based encryption tool using multiple encryption algorithms including OpenPGP, AES, SHA-1, and more.
8. TrueCrypt [Windows, Linux] – Creates virtual encrypted drives.

Miscellaneous
Here are few apps that simply didn't fit into the categories above. Although they might be unclassified, they all offer a great deal of functionality when it comes to overall system security.

1. Active Security Monitor [Windows] – Uses a proven system to determine if a user's system is secure or not.
2. PreView 1.0 [Windows] – Rates your computer on how vulnerable it is.
3. PC Security Test [Windows] – Determines the vulnerability of your computer by subjecting it to simulated attacks and malware.
4. PCPal [Windows] – Detects security vulnerabilities in your system and advises you on how to reduce their risks.
5. Simple File Shredder [Windows] – Securely and permanently delete files on your computer.
6. BCWipe [Windows] – Permanently deletes files off of your computer.
7. Permanent Eraser [Mac] – Permanently delete files from your hard drive.
8. S3 Change Explorer [Windows] – Graphically keeps track of the changes made on your system. Useful for determining if a user or file is making unwanted changes to sensitive files.
9. Process Monitor [Windows] – Microsoft's solution for monitoring all of the processes running on your computer. Useful for identifying malware instances.
10. Check Failed Password Attempts [Mac] – Tool used to scan for failed attempts logging into the administrator account.
11. CheckMate [Mac] – Compares checksums of critical files to determine their integrity before you download them. By comparing checksums you'll know if you're getting the right files, or something infected with malware.
12. Checksum Validator [Mac] – A very simple checksums comparison tool.

source :itsecurity