Computer viruses have been in existence about as long as the personal computer has been. They can cause damage to software programs creating numerous problems. In an office setting, a virus can decrease productivity. For any who unfortunately encounter a virus, it is a frustrating problem.

What is a computer virus? First of all, it helps to know what it is. A computer virus or malware is a software program that has been created by a person with the intention of causing destructive problems such as applications that spy on you, corrupt your data or give control of your computer to someone thousands of miles away. Viruses and malware are generally limited to damage to the software, however hardware can be targeted as well.

Once you suspect that you have a computer virus, what do you do? Here are some tips for computer virus removal:

Don't panic! This is the most important tip. Do not assume that you need to wipe your computer clean and start from scratch.

Determine that you have a virus. If you suspect that your computer has a virus, some symptoms may be your computer is running unusually slow, complaining with lots of errors, random reboots, blue error screens, or tons of pop-up windows. If any of this is happening, make sure you close all of your files and opened windows. Run antivirus software to make sure it is operating. Do this before updating it with the latest virus definitions. If it is operating, update your antivirus with the newest virus definitions and run it again. If it is not operating, the virus may have disabled the antivirus software. To get around this, download the software onto another computer then save to a disk or flash drive. Use the disk or flash drive to load the software onto the computer with the virus. Once loaded, scan your computer and follow the directions given to remove or disable the virus.

Start your computer in "Safe Mode". This may be an option if the antivirus program is still not working. This mode is usually is used when there is a system-critical problem that interferes with the normal operation of Windows and can help troubleshoot the problem. To start your computer in Safe Mode, you can press the F5 key or you can press the F8 key and select Safe Mode from the boot menu. Once started in Safe Mode, try running your antivirus software. This scan may find malware. If you can remove all of the malware applications found, this may correct your problem.

Hire a professional. If you've been through all of this and your PC is still having problems, it is time to call in reinforcements. There are plenty of companies which are more than happy to help. Simply check in your local phone book under "Computers; Repair and Service". When pricing these services, find a company that will take a look at your computer and give you a free estimate. They will charge hourly rates for their services.

Attention! All the hackers on the systems of various according to their sects and wishes are eager to penetrate your network, but you can defeat these attacks by providing an appropriate combination of security tactics.

Networks are daily threaded with attacks, so you need to provide permanent protection. No doubt that the most common threats are: first, the viruses, which are small programs that in reality is trying to infiltrate your network and fool the computer, entering it as an attachment with an e-mail message, beginning immediately after opening the attached file, repeating the same self in the system of your computer. Secondly, Trojan horses which run through the computer by entering the applications or data files are useful, and that is activated on the Trojans after the mediation of specific programs; even begin to take over the reins in the system of your computer.

Thirdly, the worms that are also working to replicate itself and spread to begin the search for security holes in your system, so as to penetrate your system, and often remain hidden until the right opportunity to start attack of the distributed service (DDoS). No doubt that these three types of attacks pose a major threat to his company's data and your personal data as well. Of course, you don't want or any one of the owners of companies that their networks are points of attack to distributed denial of service attacks. Therefore, we must first ensure that the protection of all devices connected to your company, and the first step to ensure this protection is to provide these devices with firewall, which is a line of defense to it.

But is it enough to spend hundreds of dollars for the provision of firewalls, or that the cost would amount to several thousands of dollars? On the walls at a minimum be equipped with an examination engine of the data package (SPI), which examines the content of packages of data and gives the right of access to your network, in the event it was free from malicious software code.

How to use the firewall?

Firewalls can also be based on certain rules or filters block the movement of inappropriate incoming and outgoing data. It can benefit the choice of Internet Protocol (IP) for example, and to prevent existing staff in the network access to the protocol specific addresses on the Internet or receiving emails from them. Firewalls can also block the movement of data in the network based on a unique identifier named " the title of control to access to the" (MAC). Many of firewalls can control in data by using filters of key words or scope, and permit data which is destined for a particular location. Firewalls also allow the creation of more sophisticated to make more complex rules for the data.

There is a better option than the firewall which is equipped with the test engine of the data packages (SPI), is the firewall, which depends on the engine of test of the deep data packages (DPI). It works great test engine (DPI) to examine the full content of the data package in addition to the advantage of examining the packet header to be performed by the firewall engine equipped with the examination of the data packages (SPI). The engines can deep packet inspection of data, during the examination of the contents of packets to discover and prevent many types of attacks: denial of service attacks, such as (DoS), and rash cache, and attacks the guise of Internet Protocol, in addition to a series of attacks by worms. The more the costs of the firewalls as become more like instruments of security, as a result of processing the applications of intent to combat viruses, spyware and virtual private networks (VPNs).

Know the firewall that you need

When the cost of the firewall is cheap, the process was prepared more easily, because the additional costs of course will provide more options, and as we know that when the number of options are increased and available, The process of the preparation of these options are more complex, so we recommend you first to learn what works well on protection, and what are the threats that want to keep away from you. For that we recommend first to write a list of all the services that users need to access, such as web sites and e-mail servers and FTP servers in addition to the messenger services and remote access of data, because the firewall can filter services on the basis of the nomination of port numbers (a way of addressing a particular service in a computer) used by these services, and Internet Protocol address of the source or destination of data. We will mention the following examples of common services outlets figures, namely: 80 of 23 service and HTTP service Telnet and FTP service for the 21 and 25 of the service SMTP.

There is no doubt that the safest way to build a list of control to access to services is beginning block all data movements, and then revisit it after the disengagement to the services required for the block one after the other, such as allowing the movement of data on port 25, if these data are bound to Internet protocol address on your e-mail in your network. If you need access to services in the internal network of computers outside your network, such as Web servers or e-mail servers, you will build more complex rules of the nomination. You can know if the firewall, which has used an outlet of the neutral area DMZ to connect with these services and to be able to isolate the services open to external networks, on the internal network, but if the firewall does not have an outlet for the neutral area DMZ, then supposed to be allowed to feature passage of the performing the work, a process in which all the movements of short data service on a particular Internet protocol address of an internal party. For those who are afraid of the topic of writing the rules for the nomination to firewalls, we say that the operations are not difficult, as appears to them, they soon learn to establish a simple set of such rules, they will learn quickly accomplish complex rules, but if they insist on their fear of the establishment of rules for the nomination, they then use specialists.

With the advent of wireless technology it has taken longer than one would have expected for printers to take advantage of this form of connection. Up until recently bluetooth was the proposed form of communication with your printer if you wanted a non wired connection. However with more and more homes now equipped with wireless routers, it makes sense to utilize this method to make more flexible use of your printer.

So what are the advantages of printing wirelessly? Firstly it frees up your printer from having to be within proximity of your computer by way of a cable connection. You can now place your printer anywhere in the home where it fits ergonomically or alternatively out of the way where it can't be easily seen. Secondly with more people owning both a desktop PC and a laptop and possibly also a netbook for the kids, they can all access the one printer without having to be connected to it. Most modern laptops are equipped with wi-fi so it is very easy to connect and print quickly and seamlessly. That means printing from anywhere in the house and even the garden if your wireless signal reaches further afield. Thirdly there is no disadvantage in using a wireless printer as they can print at the same speed as a usb connected printer.

Wireless equipped printers now come as inkjet, photo, laser and all in one models. All in one are so called as they are not only a printer but also a scanner, fax and copier providing you with an all round home office solution. Prices are now very reasonable for wireless printers and the choice of models from the major brands is growing rapidly. Like cable connected models it pays to check the cost of printer cartridges when choosing your wireless printer as this will affect your running costs, particularly if you are printing a large number of pages. In this instance a laser printer may be the best choice as it will be cheaper and more reliable for high volumes of printing.

HP, Lexmark, Epson, Canon, Brother and Kodak amongst others all now produce wireless printers. With these well known names in the market it makes sense to buy the best wireless printer for your needs, and free yourself to print anywhere in your home.

Laser toner is one of the most important components of a laser printer. It is referred to as the ink for laser printers. This toner can be in powder or liquid form packed into a toner cartridge. The cartridge is responsible for holding and controlling the ink or the toner. It is made up of hard plastic. It is inserted into a cartridge rack inside the laser printer, ready to print several pages.

Types of Laser Toner
There are two general types. The dry toner is typically used for home or company printers. It is created from a plastic powder, an amalgamation of styrene and acrylic substances. It produces different colors through the help of the added pigments. The carriers help the toner bits to be charged and be attracted into the printed material.

There are advantages in using a dry toner. It produces more materials because it does not need to penetrate the paper fiber. It means less amount of toner is used to print a page. It prints faster and there's no need for drying time. Furthermore, there is no risk of accidentally staining the printouts. Dry toner is also better for the environment. It has no harmful solvents. Dry toner has more stable colors, as well.

The other type of laser toner is the liquid toner. It is mainly of pigmented acrylic resin elements. The dye or the pigmentation enables the liquid toner to form colors. The resin particles are placed into a protecting liquid. The advantages of using liquid toner are as follows: The printer doesn't need to warm up when printing. The printed texts/images are hard to fade. It is because the printed texts/images are much more attached to the paper.

How Laser Toner Works
How does the printer use the laser toner to print texts or images? The powder is stored into a toner hopper located inside a removable casing most often referred to as the cartridge. The printer gathers the toner from the hopper with the developer unit, a small magnetic bids, charged negatively. These are attached to a rotating metal roller.

The metal roller moves the developer through the toner in the hopper. The negatively charged bids collect the positive toner particles. The roller then brushes the bids past the drum assembly. This process is called an electrostatic image, and it produces a stronger negative charge.

The electrostatic image enables the drum to pull the toner particles away. The drum moves over the paper producing an even stronger charge which collects the toner to the paper. The paper is then immediately discharged by the detac corona wire. To keep the toner on the page, the page passes through a fuser. An internal device then heats the fuser roller. This is called internal quartz tube lamps. This process melts the plastic in the toner as the page passes through.

Toners must be customized separately based on the printer brand it is meant for. There are toners which need to be ground in order to become powder. Also, there are features that need to be considered in buying a toner. These include flow rate, melting point, and thermal and magnetic qualities.

Toner Refill Kits
Toner refills are commonly offered as kits which comprise of all pieces necessary to replenish an empty toner cartridge. Toner refill kits have step by step instructions as well as are easy and fast to operate. Refilling a drain cartridge using the bottled toner that comes with the kit only takes minutes.
Refill kits are also the cheapest alternative for buying a new toner. They can save you dollars as compared to getting new cartridges. And since it is universal, it can always be used whenever you get a new printer.

This article discusses the campus protocols found in almost all enterprise networks today including spanning tree protocol, ethernet and gigabit optical fiber with a description of the current specifications and process.

Spanning Tree Protocol

Spanning Tree is an algorithm that runs on Layer 2 campus switches for preventing Layer 2 loops and broadcast storms on a network with at least 2 switches or bridges. The algorithm determines what ports at each switch or bridge must be blocked to create a loop free topology. Primary specifications are IEEE and 802.1d. The spanning tree port states are listening, learning, blocking, forwarding or disabled. Each group of switches will elect a root bridge as part of determining what switch ports must be blocked for a loop free topology. The root bridge is selected by default as the switch with the lowest priority (MAC address). Root bridge selection can be changed with the bridge priority command. It is important to consider your campus switch design and if necessary modify the root bridge selection for performance.

Newer switches that use VLAN's run one spanning tree instance per VLAN. This is important to note since Layer 2 loops occur per VLAN or segment. This allows a switch with dual connections to the same switch or different switches to load balance across those links without the concern of creating a broadcast storm. This is accomplished by assigning two VLAN's to a switch that has dual links to different campus core switches. Each link is configured to forward traffic from one VLAN and block it on the second link. For instance, consider a switch that is assigned 24 ports to VLAN 10 and 24 ports to VLAN 20 and a supervisor engine with 2 Gigabit ports that connect to different core switches. VLAN 10 is assigned to port A and VLAN 20 to port B. If traffic from VLAN 10 were allowed on port B as well, you would have a loop since traffic could leave on port A and return on port B assuming there is a trunk connection between the campus core switches.

Ethernet

This is the most popular campus data link protocol running today. The primary specifications today are 10BaseT, 100BaseT, and Gigabit Ethernet. Many networks today are comprised of 10BaseT and 100BaseT from the desktop and server to the campus switch. Gigabit Ethernet is used from switch to switch and building-to-building. 10BaseT is a specification for 10 Mbps over unshielded twisted pair category 3 cable (UTP). The distance from desktop to switch is 100 meters maximum. The 100BaseT specification is the same except the speed is 100 Mbps over unshielded twisted UTP) pair category 5 cable. Gigabit is a specification for 1000 Mbps across Fiber, STP and UTP cabling. Ethernet uses CSMA/CD as a method of dealing with collisions when two desktops are sending data simultaneously. Both workstations wait for a specified and different length of time before attempting re-transmission. The maximum packet size or MTU of an Ethernet packet is 1518 Bytes.

Optical Fiber Technologies

Gigabit Ethernet uses Multi-Mode Fiber (MMF) and Single Mode Fiber (SMF) for data transmission. Single Mode Fiber uses only one mode of light to travel across the fiber strand using a laser as the light source. Multimode allows for many modes of light to travel across the fiber strand at different angles using an LED as a light source. Modal dispersion results from different light modes transmitted across a fiber strand. The result is that Single Mode Fiber is higher bandwidth and transmits across greater distances. Multi-Mode Fiber is supported with 62.5 micron and 50 micron diameter fibers. The 50-micron fiber will transport across longer distances than 62.5 micron fiber. Multi Mode Fiber uses Short Wave Lasers (SX) and Long Wave Lasers (LX) for Gigabit transmission. Single Mode Fiber is supported with a 9 micron diameter fiber core. It uses long wave lasers to send data between buildings that are 10 kilometers apart.

Hierarchical Model

A hierarchical model is a modular design for an enterprise network that defines three specific layers that each has network services associated with those layers. The layers are access, distribution and core. The access layer is associated with branch offices that usually run lower speed circuits. These branch offices are aggregated at a distribution office and several distribution offices are aggregated at a core office. Modular designs are more scalable and utilize bandwidth more effectively than flat networks.

Access Level Services

Static Routing, Encryption, Compression, Load Balancing, Access Control Lists, VLAN's, Proxy Services, Queuing

Distribution Level Services

Summarization, Redistribution, Network Address Translation, Protocol Translation, Quality of Service, Inter-VLAN Routing, Access Control Lists (applications, protocols and services)

Core Level Services

Traffic Optimization, Path Optimization, Encapsulation, Quality of Service, Load Balancing

Topologies

The following describes the most common network wan topologies implemented in an enterprise environment.

Hub and Spoke

Each spoke has one or more links to a hub office that will connect the spoke offices. It is the least expensive and easiest to manage. There isn't any circuit diversity unless backup circuits are provisioned at each office. If a circuit fails at a spoke office and there is no backup circuit, that spoke office is without network access.

Partial Mesh

With a partial mesh topology any office could be designated as a hub office. This is more expensive than hub and spoke since there are alternate circuits to different offices. If one link fails that doesn't affect any office since a new route will be discovered with the routing protocol. The bandwidth at each circuit will affect what preferred routes are selected under normal operating conditions.

Full Mesh

This is the most expensive topology type since there is any - any connectivity among all offices. It is the most difficult to manage although most reliable with multiple paths to any destination. For companies such as banks that require 99.999% availability, this topology would be employed.

Online digital aerial maps have become easily accessible in recent years. Today, you can go online and look up any city you want on Google Maps and get a close-up view. There are also a lot of other cool views to be found though, such as ones taken from passing map survey planes that give you a bird's-eye view of manmade landmarks and famous natural attractions. Here are a few of the things you can see with the power of aerial and satellite imaging.

Manmade Landmarks
You can literally spend hours on Google Earth zooming in an out of all the world's major manmade landmarks. It has become one of the most popular time-killers amongst computer users today. Seeing the Great Wall of China from the point of view of an orbiting satellite, for example, can give you a true sense of its size. Just the fact that's visible form space and covers a good portion of the Earth. One particularly interesting city that's full of interesting landmarks is the city of Ashgabat, in Turkmenistan. The aerial map of this city is filled with giant monuments built by the late dictator of the country, Saparmurat Niyazov. From an overhead POV, the place looks like a tapestry of huge, complex symmetrical designs.

Natural Landmarks
It's also a lot of fun to browse the web for aerial images of the world's natural marvels. There are plenty to see in the U.S. alone. The rainbow-colored hot springs of Yellowstone National Park, the huge gorge made by the Rio Grande, and the snow caps of California's Sierra Nevada are all incredible sights, especially when shot from low flying survey planes, which provide clearer images and angled views.

Google Street View
But perhaps the most popular feature of online digital mapping technology today is the ability to zoom in to get a street-side view of almost every major city in the world. I'm talking of Google Map's street view feature, of course, which allows you to go to almost any city in the map and get a virtual tour of it. The images used for street view mode are taken from thousands of van-mounted cameras throughout the world that work every day to keep street view mode as up to date as possible. If you spend enough time exploring, you can find some pretty interesting candid shots. Everything from a freeway car wreck to a guy who obviously drank a little too much the night before.

You may find yourself overwhelmed looking for keywords that fit your website description and that will be profitable to you in search rankings. The internet has a variety of keyword tools that one can utilize. Why not start with the most popular search engine Google. Google Adwords has a keyword tool you can use. When using the Google Adwords Keyword Search Tool you can enter a keyword, a phrase, or you can even enter your website URL.

Being able to enter your website URL is an amazing tool if you are stuck and can't think of any keywords. Google will go to your website and read it and then return results for what they think are good keywords for you. Google will show return results with suggested keywords, as well as your advertiser competition, the local search volume of the keyword for the previous month and the global search volume.

After looking at keywords on Google you may want to head over to Keyword Discovery. Keyword Discovery has an amazing keyword tool. When searching for keywords it will return the top one hundred keyword searches. Not only will Keyword Discovery return the top one hundred searches and tell you how many people searched for that term in a month, but they also tell you what percentage of those searches were on what search engines.

Keyword Discovery collects data from all the major search engines, which could help you determine where to advertise or what search engines to get your site most listed with. Remember, study all the keywords and data given and choose your keywords very carefully. The keywords you do choose to use for your website and the most important way for people to find your website. Some keywords may be so saturated with advertiser competition (people who pay to have their website listed first) that you may want to go with a different keyword. After choosing your keywords and your website is ready you can go to the different search engine and register your site. The different search engines will go to your site and collect information and then list your website in the search engine. This may take a few weeks but you can be listed with search engines for free.

A robot is a complex assembly of several parts and devices which are synchronized to perform specific functions. Whether you are a robot hobbyist or a robotic technician, you require robot parts to customize or repair the structure. However, proper care is required while buying robot parts to ensure that they align with the system.

Essential Robot Parts

Some of the most crucial robot parts are:

Robot sensors: Robots' intelligence depends highly on their sensors. The sensors detect elements in the surrounding environment and send information to the controller. Based on this information, the controller makes its decisions. Generally, a robot has several sensors to scan the environment. Sensors can include ultrasonic range finders to measure point distances, laser scanners to measure 2D and 3D distances for mapping, sound sensors, light sensors and more.

Microcontrollers: Microcontrollers act as the brain of robotic projects. These devices work similar to the central processing unit of the computer. They are capable of collecting information, processing it and deciding the actions of the robot.

Motor: A motor converts electricity into mechanical motion. There are different types of motors, which differ in terms of size, functionality and the amount of power they generate. Motor controller: This device acts as an intermediate between a microcontroller and a motor. A microcontroller is not capable of proving enough power to a motor so instead it sends commands to a motor controller which handles the higher power requirements.

Mechanical parts: Mechanical parts come in different forms and shapes. Mechanical parts are chosen based on the specific objectives of a robot. Certain common mechanical parts are wheels, tracks, casters, connectors, motor mounts, pan and tilt systems, gear boxes, chassis/frame and grippers.

Power system: Most robots require a battery to function. Many employ a Nickel Metal Hydride (NiMH), Nickel-Cadmium (NiCd) or Lithium-ion (Li-ion) battery, though others may use alkaline, lead acid or other less common types. Some robots are powered or recharged by solar energy. Standard power equipments often include battery, charger and adapters.

Communication devices: Optimum performance of a robot depends on successful communication. Robotic structures come with sophisticated communication and control devices for transmitting and processing messages. Essential communication devices include modem, Bluetooth, remote control and telemetry.

Purchase robot parts from authorized sellers who possess considerable industry experience. RobotShop is an internationally renowned source for buying robotic parts.

Lets face it, computers and the internet have become part of our everyday life.

Information is readily available and just a keystroke away. But what if you don't want people to know your privacy information? What if you don't want people to know you have been looking at inappropriate material? Then you need to know how to cover your tracks.

You need to realize that everything you do on the internet, leaves a trace, an electronic footprint on your machine that others can see. For this reason, it is important that you know how to retain control of your privacy and delete your history.

There are many programs for sale that will do this for you automatically, but for most people it is just a matter of knowing how to delete your history in the various browsers and software that are out there today.

For example, Firefox has the option to Clear Recent History from the Tool menu, but you can also set it up so it deletes your history, cookies, etc every time you exit FireFox. This is definitely a good thing to setup if you don't want people to see your history.

Microsoft operating systems and programs also retain history settings, such as Windows Media Player, so it is important not just in the browsers to make sure you delete your history, but also in the other applications.

So what sort of history do I leave behind? The answer is quite a lot. Most browsers will have the following things that get cached on a users machine.

Internet Browser History
Your web browser stores all of your history, this includes a list of every web site you have previously visited, every search string you have performed in the various search engines (Google, Yahoo, Live), information you have entered on websites and much much more.

Browsing History can be both convenient and inconvenient. It is useful if you have visited a site and later forget what the address was. Simply pulling up the History window you can find out what the address is. Of course there may also be times when you do not want other users of your computer to see or access such information. For example, if a friend or family member shares your computer, you might prefer that they not to be able to see what websites you've visited or what files you've downloaded.
Browser Cache or Temporary Internet Files

This stores copies of web pages, images, and media that are saved for faster viewing. Even though this isnt the Browsing History users can still get a good idea of what sites you have visited by looking at this data.

Cookies
A cookie is a file created by a website that stores information on your computer, such as your preferences when when visiting that site. An example of cookie is when a web site has a "Remember This" checkbox.Ticking the check box will create a cookie on your computer and subsequent visits to that site will remember you settings.

Saved Form and Search History
Contains a list of phrases you have entered in text fields, such as web searches, and name and address fields.

Download History
Keeps a list of files you've downloaded.

Offline Website Data
Information that web sites have stored on your computer for use without an internet connection.

Saved Passwords
Contains a list of usernames and passwords that you have specified for your browser to remember.

As you can see this is just for the browsers, when you start including other history that is left behind by other 3rd party applications the problem grows.