Network Devices-Hub, Switch and Router

A network is a group of multiple networking devices connected together for data sharing. As a group networking devices have a single purpose which securely transfers data as fast as possible. To achieve this goal there are several networking devices like bridge, hub, switch, and the router is being used. Here in this article, we will discuss important networking devices.

Hub

Hub is a network technology but not really used in modern networks. In networking it is just studied because it is helpful to understand switch if somebody understands it then he can easily understand a switch.

It is a device that simply copies a data which received on any port to all its ports.  So, if a packet of data arrives on interface 1 of a 5 port

[caption id="attachment_223" align="alignright" width="300"] network hub[/caption]

hub, It will blindly copy that data out the interfaces 2 through 5.

It's a common connection point for devices in a network. It is commonly used to connect segments of a LAN. 

It was a cheap and quick way to link up multiple computers in early days.  The main issue with hubs though is that only one computer can talk at a time.  If two computers talked at the same time, their traffic would get combined as it was echoed out the other interfaces.  This is called a collision, and it would corrupt the data being transmitted by both computers. So, each computer would have to try again, after a random time period.  This becomes a real problem when the network gets busy or when more than a hand full of computers are on a network.  A switch solves the collision issue. Hub is single broadcast and single collision domain.

Switch

An Ethernet Switch is a device which is used to connect multiple computers and devices within  LAN. Its operate at Layer Two (Data Link Layer) of the OSI model. Some switches also operate at layer 3( Network Layer). These switches referred to as Layer 3 switches or multilayer switches.

switched network

Basic Function of a Network Ethernet Switch and a Network Ethernet Hub are
same. That is to forward Layer 2 packets (Ethernet frames) from source device to destination device. But a Network switch is more intelligence than a hub. Because an Ethernet switch uses MAC addresses to make forwarding decisions. It is completely unaware of the protocol being carried in the data portion of the frame; such as an IPv4 packet. The switch makes its forwarding decisions based only on the Layer 2 Ethernet MAC addresses.

Unlike an Ethernet hub that repeats bits out all ports except the incoming port; an Ethernet switch consults a MAC address table to make a forwarding decision for each frame. The MAC address table is sometimes referred to as a content addressable memory (CAM) table.

Network Switches of different input and output bandwidths are available. Today’s Ethernet Network Switches can have bandwidths of 10, 100, 1000 or 10,000 Megabits per second.

Switch Features and Advantages

• Connect network devices together in a Local Area Network (LAN).


• Its learn Layer 2 (MAC) addresses and forward Layer 2 packets (Ethernet frames); to exact destination with the help of device mac address


• It’s control of who has access to various parts of the network.


• Provision to monitor network usage.


• High-end switches have pluggable modules.


• Allow to connect multiple device and port can be managed; VLAN can create security also can apply


• First broadcast; then unicast & multicast as needed.


• Switches use content accessible memory CAM table which is typically accessed by ASIC (Application Specific integrated chips).


• Half/Full duplex


• Connecting two or more nodes in the same network or different network


• The switch has one broadcast domain [unless VLAN implemented]

Router

A router is defined as a device that selects the best path for a data packet. It is located at any gateway (where one network meets another) further It is a part of a network switch.

Its forward data packets from one network to another based on the address of the destination network in the incoming packet and an internal routing table. It’s also; determines which port (line) to send out the packet (ports typically connect to Ethernet cables). Routers also require packets formatted in a routable protocol. The global standard being TCP/IP, or simply “IP.” Routers operate at Layer 3 (network layer) of the OSI model and it uses the destination IP address in a data packet to determine where to forward the packet. Router store IP address in Routing table and maintain address on its own.

Computer Virus and Top ten destructive virus in the world

Computer Virus

A computer virus is a program, script, and macro which is planned to cause harm; steal private information, modify data, send e-mail and display messages. More importantly, when the virus is executed then it spreads by
copying itself into or over the following:-

• Data files


• Programs


• Boot sector of a computer's


• Hard drive


• Potentially anything else writable.

Virus writers use detail knowledge of security vulnerabilities to gain access to a host's computer.

When was term “Virus” first Used

The theory of a computer program capable of reproducing itself was first mentioned byJohn von Neumann in his 1949 "Theory of self-reproducing automata" essay.

First computer virus ever created.

Elk Cloner was the first computer virus written by Rich Skrenta in 1982. He was a 15-year old high school student at the time. The Elk Cloner virus spread to other computers by monitoring the floppy drive and copying itself to any floppy diskette. Once a floppy was infected it would infect all other computers that used the disk was. A computer that was infected would display a short poem on every 50th boot.

How to protect your computer from a viruses

Anti-virus software is the solution to protect a computer from viruses. Once installed on a computer an antivirus monitors, detects, and cleans any computer viruses.

Examples of computer viruses

There are many types of a computer virus such as:-

• Appending virus


• 
  

  Boot sector virus

  
  


• 
  

  Space filler virus

  
  


• 
  

  Cavity virus

  
  


• 
  

  CMOS virus

  
  


• 
  

  Companion virus

  
  


• 
  

  Encrypted virus

  
  


• 
  

  Exe Virus

  
  


• 
  

  Rabbit Virus

  
  


• 
  

  MBR virus

  
  


• 
  

  Non-resident virus

  
  


• 
  

  Overwrite virus

  
  


• 
  

  Stealth virus

  
  

History of computer viruses is too long and it is very difficult to cover it in a single article. in the following, I am giving the list and short introduction of 10 most destructive viruses in the world ever.

10 Most destructive virus in the world

1. ILOVEYOU

The ILOVEYOU is considered one of the most virulent computer virus ever created. The virus managed to wreck havoc on computer systems all over the world; causing damages totaling in at an estimate of $10 billion. 10% of the world’s Internet-connected computers were believed to have been infected. The virus was created by two Filipino programmers, Reonel Ramones and Onel de Guzman.

2. Code Red

code red was discovered by two eEye Digital Security employees in 2001. The pair were drinking Code Red Mountain Dew at the time of discovery so its name become code red. The worm targeted Microsoft IIS web server installed computer and exploiting a buffer overflow problem in the system. It leaves a very little trace on the hard disk as it is able to run entirely on memory, with a size of 3,569 bytes. Once infected, it will proceed to make a hundred copies of itself but due to a bug in the programming; it will duplicate even more and ends up eating a lot of the resources of the system.

3. Melissa

in 1999 Melissa was created by David L. Smith. It started as an infected Word document that was posted up on the alt-six USENET group, claiming to be a list of passwords for pornographic sites. This got people curious and when it was downloaded and opened, it would trigger the macro inside and unleash its payload. The virus will mail itself to the top 50 people in the user’s email address book and this caused an increase in email traffic and disrupting the email services of governments and corporations. It also sometimes corrupted documents by inserting a Simpsons reference into them.

4. Sasser

 it was created by computer science student Sven Jaschan in 2004. it slows down and crashes the computer while making it hard to reset without cutting the power; the effects were incredibly disruptive, with millions of computers being infected, and important, critical infrastructure affected. The worm took advantage of a buffer overflow Vulnerability in Local Security Authority Subsystem Service (LSASS); which controls the security policy of local accounts causing crashes to the computer. It will also use the system resources to propagate itself to other machines through the Internet and infect others automatically.

5. Zeus

It's a Trojan horse made to infect Windows computers so that it will perform various criminal tasks. The most common of these tasks are usually man-in-the-browser keylogging and form grabbing. The majority of computers were infected either through drive-by downloads or phishing scams. First identified in 2009.

6. Conficker

Also known as Downup or Downadup, Conficker is a worm of unknown authorship for Windows. It was first to appear in 2008 and its name comes from the English word, configure and a German pejorative.It infects computers using flaws in the OS to create a botnet. It's a malware and was able to infect more than 9 millions computers all around the world, affecting governments, businesses, and individuals.

7. Stuxnet

Israeli Defence Force and American Government created, Stuxnet is an example of a virus created for the purpose of cyber warfare, as it was intended to disrupt the nuclear efforts of the Iranians. It was estimated that Stuxnet has managed to ruin one-fifth of Iran’s nuclear centrifuges and that nearly 60% of infections were concentrated in Iran.

8. Mydoom

Mydoom was a worm for Windows appeared in 2004 that became one of the fastest spreading email worms since ILOVEYOU. The author is unknown and it is believed that the creator was paid to create it since it contains the text message, “Andy; I’m just doing my job, nothing personal, sorry,”. It was named by McAfee employee Craig Schmugar, one of the people who had originally discovered it. ‘mydom’ was a line of text in the program’s code (my domain) and sensing this was going to be big, added ‘doom’ into it.The worm spreads itself by appearing as an email transmission error and contains an attachment of itself. Once executed, it will send itself to email addresses that are in a user’s address book and copies itself to any P2P program’s folder to propagate itself through that network. 

9. CryptoLocker

CryptoLocker a form of Trojan horse targeted at computers running Windows. It uses several methods to spread itself, such as email, and once a computer is infected, it will proceed to encrypt certain files on the hard drive and any mounted storage connected to it with RSA public key cryptography. While it is easy enough to remove the malware from the computer, the files will still remain encrypted. 

10. Flashback

The Trojan was first discovered in 2011 by antivirus company Intego as a fake Flash install. In its newer incarnation, a user simply needs to have Java enabled (which is likely the majority of us). It propagates itself by using compromised websites containing JavaScript code that will download the payload. Once installed, the Mac becomes part of a botnet of other infected Macs.

Reformed hacker offers insight into cyber crime

Ne amores quidem sanctos a sapiente alienos esse arbitrantur. Sin autem eos non probabat, quid attinuit cum iis, quibuscum re concinebat, verbis discrepare? Hoc enim identidem dicitis, non intellegere nos quam dicatis voluptatem. Itaque hic ipse iam pridem est reiectus; Tu vero, inquam, ducas licet, si sequetur; At certe gravius. Illum mallem levares, quo optimum atque humanissimum virum, Cn. Etenim semper illud extra est, quod arte comprehenditur.

Omnes enim iucundum motum, quo sensus hilaretur.

Negat esse eam, inquit, propter se expetendam. Sed virtutem ipsam inchoavit, nihil amplius. Similiter sensus, cum accessit ad naturam, tuetur illam quidem, sed etiam se tuetur; Non enim iam stirpis bonum quaeret, sed animalis. Efficiens dici potest. Ergo, si semel tristior effectus est, hilara vita amissa est?

• Tu enim ista lenius


• Quod eo liquidius faciet


• Apud ceteros autem philosophos


• Qui quaesivit aliquid, tacet;


• Sed quia studebat laudi et dignitati

Poterat autem inpune; Etsi qui potest intellegi aut cogitari esse aliquod animal, quod se oderit? Quamquam id quidem licebit iis existimare, qui legerint. Tu enim ista lenius, hic Stoicorum more nos vexat. Quod eo liquidius faciet, si perspexerit rerum inter eas verborumne sit controversia.