Virus and Spywares

Virus
A computer virus is a computer program that can copy itself and infect a computer. You should take care of your computer learning about how to protect your pc from virusers.

How to combat virus
-The basic one is to install a good antivirus program in your pc.

The best way to protect your network from virus infection is to use an antivirus program.

A antivirus program can detect and remove

This sofware help you keep your computer clean an free o virus.

-Just enter to the web page you trust
-Dont open weird email


Spywares
Spyware is a type of malware that is installed on computers and collects little bits of information at a time about users without their knowledge.

Remedies and prevention
As the spyware threat has worsened, a number of techniques have emerged to counteract it. These include programs designed to remove or to block spyware, as well as various user practices which reduce the chance of getting spyware on a system.
Anti-spyware programs can combat spyware in two ways:

They can provide real time protection against the installation of spyware software on your computer.
Anti-spyware software programs can be used solely for detection and removal of spyware software that has already been installed onto your computer.

Computer Security

Computer security is the process of preventing and detecting unauthorized use of your computer. Prevention measures help you to stop unauthorized users from accessing any part of your computer system. Detection helps you to determine whether or not someone attempted to break into your system, if they were successful, and what they may have done.

some tips for your security

1. Make sure you have a security policy in place. this can help you keep the rule in your organisation should define the level of security and the roles and responsibilities of users, administrators and managers.

2. Keep your systems patched will close vulnerabilities that can be exploited by hackers.

3. Have a network device inventory this help you keep control of the item you have in your network.

4. Scan TCP/UDP services -— Turn off or remove unnecessary services.

5. Set a strong password.

6. Don't trust code from non-trusted sources.

7. You should block the web page you don't trust.

8. Don't provide more rights to system resources than necessary.

9. Have a good firewall in your pc.

10. Clean your computer every month at least

how to create a twisted cable

Things You'll Need:
Twisted network cable spool (no RJ45 ends)
RJ45 Modular Jacks
RJ45 Crimping Tool
Scissors

Step 1
Using the crimping tool, insert ¾ inch of the twisted network cable end and remove the cable's coating. You can also use a pocket knife or scissors to strip the wire. Be sure not to cut the wires.
Step 2
Untwist the wires so you have eight individual wires. Sort them in the following order from left to right: Orange White, Orange, Green White, Blue, Blue White, Green, Brown White, Brown.
Step 3
Use the scissors to trim the edges of the wires so all wires are the same length.
Step 4
Insert the wires into a modular jack. Insert with the hook side facing down or away from you. Be sure the wires are inserted completely to the top of the modular jack. Part of the coating should be inserted into the jack as well. If not, remove the wires and trim the wires slightly until part of the coating inserts into the modular jack.
Step 5
Insert the modular jack into the RJ45 slot in the crimping tool. Press the tool together firmly until you hear a small snap. Pull out the modular jack and tug on the cable to be sure the wires are held firmly in place.
Step 6
Measure out the length of cable you need and use scissors to cut the twisted network cable. Repeat the above process on the second end of the cable

Topology in Network Design

Network Topology
A network consists of multiple computers connected using some type of interface, each having one or more interface devices such as a Network Interface Card (NIC) and/or a serial device for PPP networking. Each computer is supported by network software that provides the server or client functionality. The hardware used to transmit data across the network is called the media. It may include copper cable, fiber optic, or wireless transmission. The standard cabling used for the purposes of this document is 10Base-T category 5 ethernet cable. This is twisted copper cabling which appears at the surface to look similar to TV coaxial cable. It is terminated on each end by a connector that looks much like a phone connector. Its maximum segment length is 100 meters.

Network topologies are categorized into the following basic types:
· bus
· ring
· star
· tree
· mesh

• . Hybrid topology

More complex networks can be built as hybrids of two or more of the above basic topologies.

Bus Topology
Bus networks (not to be confused with the system bus of a computer) use a common backbone to connect all devices. A single cable, the backbone functions as a shared communication medium that devices attach or tap into with an interface connector. A device wanting to communicate with another device on the network sends a broadcast message onto the wire that all other devices see, but only the intended recipient actually accepts and processes the message.
Ethernet bus topologies are relatively easy to install and don't require much cabling compared to the alternatives. 10Base-2 ("ThinNet") and 10Base-5 ("ThickNet") both were popular Ethernet cabling options many years ago for bus topologies. However, bus networks work best with a limited number of devices. If more than a few dozen computers are added to a network bus, performance problems will likely result. In addition, if the backbone cable fails, the entire network effectively becomes unusable.

Ring Topology

In a ring network, every device has exactly two neighbors for communication purposes. All messages travel through a ring in the same direction (either "clockwise" or "counterclockwise"). A failure in any cable or device breaks the loop and can take down the entire network.
To implement a ring network, one typically uses FDDI, SONET, or Token Ring technology. Ring topologies are found in some office buildings or school campuses.

Star Topology Many home networks use the star topology. A star network features a central connection point called a "hub" that may be a hub, switch or router. Devices typically connect to the hub with Unshielded Twisted Pair (UTP) Ethernet.
Compared to the bus topology, a star network generally requires more cable, but a failure in any star network cable will only take down one computer's network access and not the entire LAN. (If the hub fails, however, the entire network also fails.)

Tree Topology Tree topologies integrate multiple star topologies together onto a bus. In its simplest form, only hub devices connect directly to the tree bus, and each hub functions as the "root" of a tree of devices. This bus/star hybrid approach supports future expandability of the network much better than a bus (limited in the number of devices due to the broadcast traffic it generates) or a star (limited by the number of hub connection points) alone.

Mesh Topology Mesh topologies involve the concept of routes. Unlike each of the previous topologies, messages sent on a mesh network can take any of several possible paths from source to destination. (Recall that even in a ring, although two cable paths exist, messages can only travel in one direction.) Some WANs, most notably the Internet, employ mesh routing.
A mesh network in which every device connects to every other is called a full mesh. As shown in the illustration below, partial mesh networks also exist in which some devices connect only indirectly to others.

A hybrid topology is a combination of any two or more network topologies in such a way that the resulting network does not have one of the standard forms. For example, a tree network connected to a tree network is still a tree network, but two star networks connected together exhibit hybrid network topologies. A hybrid topology is always produced when two different basic network topologies are connected.

Introduction to computer networks

Definition...

• A local area network (LAN) supplies networking capability to a group of computers in close proximity to each other such as in an office building, a school, or a home. A LAN is useful for sharing resources like files, printers, games or other applications. A LAN in turn often connects to other LANs, and to the Internet or other WAN.

• A metropolitan area network (MAN) is a network that interconnects users with computer resources in a geographic area or region larger than that covered by even a large local area network (LAN) but smaller than the area covered by a wide area network (WAN). The term is applied to the interconnection of networks in a city into a single larger network (which may then also offer efficient connection to a wide area network). It is also used to mean the interconnection of several local area networks by bridging them with backbone lines. The latter usage is also sometimes referred to as a campus network.

• A wide area network (WAN) is a geographically dispersed telecommunications network. The term distinguishes a broader telecommunication structure from a local area network (LAN). A wide area network may be privately owned or rented, but the term usually connotes the inclusion of public (shared user) networks. An intermediate form of network in terms of geography is a metropolitan area network (MAN).

• A personal area network (PAN) is the interconnection of information technology devices within the range of an individual person, typically within a range of 10 meters. For example, a person traveling with a laptop, a personal digital assistant (PDA), and a portable printer could interconnect them without having to plug anything in, using some form of wireless technology. Typically, this kind of personal area network could also be interconnected without wires to the Internet or other networks.

• VPN - Virtual Private Networking VPN consists of private network access over public connections. A VPN can provide secure but more cost-effective LAN-WAN communication.

• Campus Area Network
  A campus area network (CAN) is a computer network interconnecting a few local area networks (LANs) within a university campus or corporate campus. Campus area network may link a variety of campus buildings including departments, the university library and student halls of residence. A campus area network is larger than a local area network but smaller than a metropolitan area network (MAN) or wide area network (WAN). CAN can also stand for corporate area network.

• Storage Area Network (SAN) is a high-speed subnetwork of shared storage devices. A storage device is a machine that contains nothing but a disk or disks for storing data.