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Security

A VPN is a network that is constructed using public wires to connect to a private network. There are a number of systems that enable you to create networks using the Internet as the medium for transporting data. It secures security mechanisms to ensure that only authorized users can access the network and the data cannot be intercepted and also secures the private network as these systems use encryption.

IP Security (IPsec)

IP Security (IPsec) is a set of protocols used to support secure exchange of packets at the IP layer. IPsec has been deployed widely to implement Virtual Private Networks (VPNs). IPsec supports two encryption modes: Transport and Tunnel. Transport leaves the header untouchedmode and encrypts only the data portion of each packet. Tunnel mode which is more secure,encrypts both the header and the payload. On the receiving side, an IPSec-compliant device decrypts each packet. The sending and receiving devices must share a public key,for IPsec to work. This is accomplished through a protocol known as Internet Security Association and Key Management Protocol, which allows authenticate the sender using digital certificates and the receiver to obtain a public key.

Fraud over Internet Protocol(FoIP)

Fraud over Internet Protocol(FoIP) is the act of taking advantage of VoIP security vulnerabilities to steal network capacity. The term was used after a well-known criminal case where two men tapped into corporate and service provider networks and routed millions of minutes in calls illegally. One of the first uses of the term FoIP as an acronym for Fraud over Internet Protocol appeared in an article on Datamation.

Snooping Protocol Types

The processor that is writing data, before it changes its local copy,causes copies in the caches of all other processors in the system to be rendered invalid.For caches to check for a copy of the invalidated file, the local machine sends an invalidation signal over the bus. The data on the local machine can be updated until another processor requests it,once the cache copies have been invalidated.

#vpn #ip #security #protoco

unixporn

#unixporn #linux

Search Engine Optimization

The process used to keep a natural placement on organic search engine results pages is called Organic Search Engine Optimization (SEO) and the techniques used for organic SEO include: writing content,keyword analysis and keywords, backlinking and link building to improve link popularity.

Website optimization is the procedure used to optimize a website in search engines or to design it from scratch. Website optimization includes optimizing the components of your website to ensure that it improve the overall chances that the website will be indexed by search engines and ensure that it is accessible to a search engine; adding relevant keyword and phrases on the website,editing image tags and meta tags.

White hat SEO is the procedure to optimize the speed at which your website loads in a Web browser. This type of optimization generally involves editing your web with HTML or CSS code for faster loading. It's also reduces images, scripts, or video components that are needed to render the webpage. White hat refers to the optimization tactics,strategies and techniques that focus on a human audience opposed to search engines and completely follows search engine policies and rules.For example, a website focuses on relevancy and organic ranking is considered to be optimized using White Hat SEO practices. Some examples of techniques include using writing content,keywords and keyword analysis, backlinking and link building.Those who intend to make a long-term investment on their website use White Hat SEO. Also called Ethical SEO.

To increase the amount of visitors to a Web site, SEO service provider utilizes the practice of search engine optimization by obtaining high-ranking placements in the search results page of search engines (SERP). SEO services improves the chances that the site will be found and ranked highly by the search engine, and help to ensure that a site is accessible to a search engine. SEO service providers offer a wide range of options and packages for search engine optimization, ranging from one-time fees for smaller sites to monthly subscriptions for ongoing SEO efforts and support.

Data Flow

There are 3 types of communication between two devices: simplex, half-duplex and full-duplex.

Simplex

In simplex mode the communication is unidirectional. One device on a link can transmit and the other can only receive.

Traditional monitors and keyboards are examples of simplex devices. The monitor can only accept output otherwise the keyboard can only introduce input. The simplex mode use the entire capacity to send data in only one direction.

Half-Duplex

In half-duplex mode, both devices can transmit and receive, but not at the same time. When one device can only receive, the other is sending, and vice versa.

The half-duplex mode is like a one-lane road with traffic allowed in both directions. In this transmission the capacity of a channel is taken over by whichever of the two devices is transmitting at the time.For example citizens band radios and walkie-talkies are both half-duplex systems. The half-duplex mode is used when there is no need for communication in both directions at the same time and the entire capacity can be utilized for each direction.

Full-Duplex

In full-duplex mode, both stations can transmit and receive at the same time.Signals going in one direction share the capacity of the link with signals going in the other direction. The link must contain two paths, one for sending and the other for receiving; or the capacity of the channel is divided between signals traveling in both directions. One example of full-duplex communication is the telephone network.

This mode is used when in both directions communication is required all the time and in this way the capacity of the channel must be divided between the two directions.

#telecommunications #information technolog

5 Simple Steps to Protect Your PC from Hackers

In this world of ubiquitous, you must protect your computer from hackers and malware. The way how malware attacks the system is by the Internet and the Web service. There are different ways to protect and remove malware from computers but no one method is enough to ensure that computer is secure. The more layers of defense it has, the harder for hackers to use our computer. Here are five steps to protect our computer:

1.Install Firewall 2.Install Antivirus Software 3.Install Anti-Spyware Software 4.Use Complex and Secure Passwords 5.Check on the Security Settings of the Browser

Install Firewall:

The types of firewalls:software firewall and hardware firewall. Each serves similar, but different purposes. A firewall is the first step to provide security to the computer and creates a barrier between the computer and any program that is unauthorized which tries to come in through the Internet.

Install Antivirus Software:

Antivirus also protects the computer. It is a software that helps protecting the computer from unauthorized codes. Unauthorized software includes trojans, keyloggers,viruses etc. This slow down the speed of our computer,access personal information and delete important files.We must install an antivirus software to prevent the system from further attack of virus,even if our system is virus free. Antivirus software helps detecting threats computer and the information in it to be safe. This further helps to protect the PC from newly created viruses.

Install Anti-Spyware Software:

Anti-Spyware is a software program that collects information about an organization without their approval. This information is redirected to another website. Spyware are designed in a way that are not easy to be removed. Anti-Spyware software is dedicated to combat spyware.Anti-spyware software,similar to antivirus software, offers real time protection. It scans all the information and helps in blocking the threat.

Use Complex and Secure Passwords:

The first line of defence is to have strong and complex passwords. Complex passwords are difficult for the hackers to find. The password must have at least 8 characters in length include letters that are both upper and lower case,a combination of numbers and a special character. Hackers use certain tools to break passwords easily.

The Security Settings of the Browser, check it on: Browsers have different security and privacy settings that we should review and set to the level you desire. Recent browsers give us ability to tell web sites to not track your movements, increasing our security and privacy.

PROTOCOLS AND STANDARDS

Protocol is synonymous with rule while standards are agreed-upon rules.

Protocols

In computer networks, communication occurs between entities in different systems. Two entities can not send bit streams to each other and expect to be understood. To occur the communication, the entities must agree on a protocol. A protocol is a set of rules that govern data communications and it defines what is communicated, the way it is communicated and the time when it is communicated.

The key elements of a protocol are semantics,timing and syntax.

o Syntax- refers to the format of the data, it means the order in which they are presented. For example, a protocol might expect the first 8 bits to be the address of the sender, the second 8 bits to be the address of the receiver, and the rest the message itself.

o Semantics- refers to the meaning of each section of bits.

o Timing- refers to: the time that data should be sent and the way how fast they can be sent. For example, the transmission will overload the receiver and some data will be lost when a sender that produces data at 100 Mbps and the receiver that can process data at only 2 Mbps.

Standards

Standards are very important in creating and maintaining a market for equipment manufacturers and in guaranteeing national and international interoperabilitliy of data and telecommunications technology and processes.

De facto Standards are the standards that have not been approved by an organized body but have been adopted as standards through widespread use. They are often established originally by manufacturers who seek to define the functionality of a technology or a new product.

#data #information technology

DATA COMMUNICATIONS

We are sharing information, when we communicate. This sharing can be remote or local. Between individuals, remote communication takes place over distance, while local communication usually occurs face to face. Telecommunication, which

includes telephony,television, and telegraphy, means communication at a distance. The word data refers to information presented in whatever form is agreed upon by the parties creating and using the data.

Data communications are the exchange of data between two devices via some form of transmission medium.The communicating devices must be part of a communication system made up of a combination of hardware and software,for data communications to occur. The effectiveness of a data communications system depends on four fundamental characteristics: timeliness,jitter,delivery, and accuracy.

1. Delivery. The system must deliver data to the correct destination. Data must be received by the user or intended device and only by that user or device.

2. Accuracy. The system must deliver the data accurately. Data that have been left uncorrected and altered in transmission are unusable.

3. Timeliness. The system must deliver data in time. If the data delivered are late,they are useless. In the case of audio and video,means delivering data as they are produced and without delay. This delivery is called real-time transmission.

4. Jitter. Jitter refers to the variation in the packet arrival time. It is the uneven delay in the delivery of video or audio packets.

Spectrum

We mentioned compounds of lithium,strontium and lithium without specifying which compounds we were talking about. This may have given you the impression that only the spectrum of one of the elements in a compound can be observed.It is true that the flame of your alcohol burner is hot enough to produce the spectra of elements,such as oxygen and chlorine.However,if we heat a sample of a compound to a sufficiently high temperature,the spectra of all the elements in the compound will be observed.

Under such conditions the resulting spectrum is no longer simple.It will most likely contain complicated patterns of many closely spaced lines.Yet each element gives out its own spectrum,which different from that of any other.It takes accurate measurements of the positions of spectral lines to identify an element.

Once this has been done, however, the presence of that element has been definitely established.With a good instrument, it is observed that the yellow of the sodium flame is not just any yellow.It is very specific color indeed,which has its own special place in the spectrum.It is a yellow made by no other element.The presence of this particular pair of lines always means that sodium is present in the light source. Even if the yellow color is hidden from the unaided eye by many colors,the spectroscope will show the presence of sodium. Although calcium, lithium and strontium give flame tests of nearly the same color, each gives its own set of characteristic spectral lines when viewed through a spectroscope.The spectroscope thus enables us to distinguish one element from another.

#science

Weight And Weightlessness

A weight is a force. Your weight is the pull of earth's gravity on your body. Likewise,the weight of your car is the force of the earth's attraction for it. The greater the mass is, the larger the attraction is.Two identical pickup trucks weigh exactly twice as much as one. But mass and weight are not the same; they are measures of two different things,inertia and force.

For example, consider the rocks brought from the moon's surface by astronauts.Because of the Earth's stronger gravitational attraction, these rocks weigh more on Earth,about six times as much as they weighed on the moon.But their mass,their resistance to a change in velocity,is still the same;they have the same quantity of matter on Earth as they did on the moon.

Even though weight and mass are not the same,most of us do not make distinction between them, suppose someone hands you two books and asks which is the more massive.Almost certainly you would "weigh" one in each hand choose the heavier book.That's okay,because the heavier one does have more mass.But if the two books were on a smooth table,you could just push each book back and forth to see which has the larger inertia.

Perhaps nothing is so ingrained in our senses as the perpetual pulling of the earth on our surroundings.It's always there, never changing.It's been hugging solids,liquids and gases to the earth's surface for over 4 billion years. Earth's gravity is built into our descriptions of our world with words like up,down and weight.

To measure your weight you can use a bathroom scale, which is a spring that stretches if it is pulled.As you step onto the scale, the spring's pointer register a larger and larger force until you are at rest, supported entirely by scale. The scale then shows you how much force balances gravity's pull on your mass and this force is equal to your weight.If you step down and drink two cups coffee and then step back on the scale,you'll weigh about 1 pound more. But suppose some fellow strapped a small scale to his feet and jumped from the top of the stepladder. You can imagine what would happen,although you should not actually try it. While he was falling, the scale would fall with him, it wouldn't support him and he couldn't press against it. In this situation, the scale would show a reading of zero. Gravity's pull would still be there, of course, pulling on him as he fall.He would be no supporting force opposing the gravitational pull,so he would feel weightless.

Making Models

We use models, in everyday life and in science, as a method of simplifying and making sense of everything we observe.

A model is a way of explaining something difficult in terms of something more familiar. For example there are many model used to describe how the brain works.It's like a telephone exchange-nerves carry messages in and out from various parts of body.The brain is like a library, like a computer, it has something in common with all these thing, but yet it's different from them all.These are models,which have some use, but inevitably a model also has its limitations.

You have probably come across various models used to explain electricity. We cannot see electric current in a wire, so we find different ways of explaining what is going on. Current is like water flowing in a pipe.A circuit is like a central heating system. It is like a train carrying coal from mine to power station.All of this models conjure up some useful impressions of what electricity is, but none is perfect.

We can make a better model of electric current in a wire using the idea of electrons. Tiny charged particles are moving under the influence of an electric field. We can say how many there are,how fast they are moving under the influence of an electric field. We can say how many there are, how fast they are moving and we can describe the factors that affect their movement. This is a better model,but is harder to understand because it is further from our everyday experience. We need to know about electric charge,atoms and so on.

Most people are happier with more concrete models,as your understanding of science develops, you accept more and more abstract models.

Ultimately,you may have to accept a model that is purely mathematical-some equation that give the different observations.But which should we use in a particular situation? For a long time Newton's view prevailed - light travels particles.He could use this model to explain both reflection and refraction.His model suggested that light travels faster in glass than in air.We now know that this is not the case and this caused difficulties for the particle model. Young showed both diffraction and interference of light and this convinced most of people that light travels as waves.

One of the experiments that convinced nineteenth- century physicists that light is a wave was Young;s double-slit experiment. A beam of light is shone on a pair of parallel slits overlaps, an interference pattern is formed. We interpret these results using a wave model light.At a point on the screen,light waves are arriving from each slit.Constructive and destructive interference result in this interference pattern. The particle model of light can not explain this pattern.If two particles of light arrived together, we would except double brightness.We can not imagine two particles arriving together and canceling each other out.

#models #physics #science

THERE IS NO GRAVITATIONAL PULL... ONLY PUSH!

The Italian and astronomer Galileo discovered that all objects fall toward the earth with the same acceleration,size, shape or regardless of their weight,when the gravity is the only force acting on them. Nicolaus Copernicus had proposed a heliocentric in which the planets moved in circles around the sun. Galileo also had a theory about the universe,which he based on the ideas of the Polish astronomer Copernicus.

The ancient Greek philosophers developed several theories about the force that caoused object to fall toward the earth. Aristotle proposed that all things were made from some combination of the four elements ,air,earth,water and fire.Object with more earth in them,were attracted to the earth. Fire was tended to rise from the earth.Aristotle also developed a theory describing the universe that was geocentric, with the moon, sun,planet and stars moving around the earth on spheres. Philosophers did not propose a connection between the force behind planetary motion and the force that made objects fall toward the earth.

The Italian physicist and astronomer Galileo discovered that all objects fall toward the earth with the same size,acceleration, shape or regardless of their weight when gravity is the only force acting on them.In the mid of 16th century, Copernicus had proposed a sun-centered system in which the planets moved in circles around the sun and Galileo agreed with cosmology. Galileo saw no connection between the force planetary motion and gravitation on earth. He believed that the planets moved in circles because this motion was the natural path of the body.

THERE IS NO GRAVITATIONAL PULL... ONLY PUSH!

Meaningful error messages

Program: *crash for no apparent reason*

Sysadmin: Why did you crash?

Program: Because something went wrong.

Sysadmin: What went wrong?

Program: Something.

Sysadmin: I need more detail. Increasing log level.

Program: Something bad went wrong.

Sysadmin: I need more than that. Increasing log level again to max level.

Program: Fuck you. Here's a 42GB hex dump of system memory. Figure it out yourself jackass.

Sysadmin: *picks up a crowbar and goes off to find the programmer*

#nixcraft

nixcraft

As an IT/sysadmin person I can confirm that, technically, this would work.

Scopes of Physics

Physics us a science dealing with constituents of the universe, the forces they exert on one another and the result produced by these forces. It is emerged as a separate science only in the early 19th century;until that time a physic it was often also a biologist,philosopher,mathematician,engineer or even primarly an artist or political leader.This field has grown to such an extent that with few excpetions modern physicists have to limit their attention to one or two branches of the science.When the fundamental aspects are discovered, they become the domain of scientists and other engineers.

Microscopic approach is the emphasis on the interaction between particles in modern physics, which must often be supplemented by a microscopic approach that deals with larger elements or systems of particles.

Thermodynamics is a branch of physics, deals with the elucidation and measurement of properties of a system as a whole and remains useful in other fields of physics;it also forms the basis of much of chemical and mechanical engineering.Such properties as the pressure, volume ,and temperature of a gas have no meaning for an individual atom or molecule;these thermodynamic concepts can only be applied directly to a very large system. Between the microscopic and macroscopic approach;statistical mechanics,indicates hoe pressure and temperature can be related to the motion of atoms and molecule on a statistical basis.

Optic

Spectral analysis or spectroscopy can be done on tiny quantities of matter such as very small sample of a rare mineral. Spectroscopy can even be used to determine the presence of different elements in distant object like our sun and other stars.Analysis of sunlight was one of the very early uses of spectroscope in the study of unknown matter. Most of the spectral lines observed in the sunlight could also be produced with known material in the laboratory.

However,during a solareclipse in 1868, a new set of spectral lines was found in the spectrum of the light coming from the edge of the sun. This set of lines had never been seen before and could not be produced with any element known at the time. This lines were therefore thought to be from a new element,which was given the name "helium" after the Greek word of sun. Eventually, the element was also detected on earth through the use of a spectroscope. Cacium,lithium and strontium give flame tests of nearly the same color, each gives its own set of characreristic spectral lines when viewed through a spectroscope. The spectroscope thus enables us to distinguish one element from another.

During the first few years of spectroscopy, five new elements were discovered that are presentation earth in such a small concentrations that they were previosly unknown. In analyzing the spectrum of minerals founnd in the water of certain spring in Germany, two lines of unknown origin were found in the blue region of spectrum.This bit of evidence was enough to challenge Robert Bunsen to search for a new element in the water.Spectral analysis has been one of the tools found helpful in identifying some of the new elements produced by nuclear reactions.

Time after time, this interplay between chemical analysis and spectral analysis has caused complex substances to yeild the secret of their composition. Invariably, the results given by these two different methods agree completely.

COMPUTER TYPES

A typical computer consists of two parts: hardware and software.

Hardware is any mechanical part that you can touch or see. Software is a program which tells a computer what to do.

CPU is a microprocessor chip which processes data and coordinates the activities of all other units. The main memory holds the instructions and data which are being processed by CPU. It has two main sections: Random access memory and Read only memory.

Peripherals are the physical units attached to the computer. They include: Input devices: let us enter data and commands

Output devices: let us extract the result

Storage devices: we use to store information permanently

1.A desktop PC has its own processing unit, monitor and keyboard.It is designed to be placed on your desk and is used as a personal computer at home or as a workstation for a group work.Some models have a vertical case called tower.

2.A mainframe is the most powerful type of computer. It can process and store a lot of data. It could supports multiple users at the same time and can support more simultaneous processes than a PC. The central system is a large server connected to hundreds of terminals over a network.

3. A laptop is a lightweight computer that you can transfer easily. It can work as fast as a desktop PC with similar disk drives, processors and memory capacity. Instead of a mouse it can has a touched pad.

4.A tablet PC has a LCD screen on which you can write using a special digital pen. Your handwriting can be recognized and converted into editable text.

The laptop versus desktop dilemma was usually decided by whether mobility or performance was more important to you. Oftentimes, gamers and designers went for desktop,while students and remote workers chose laptops. Fortunately, computer technology has come a long way since the days of laptops with limited battery of life and desktop with cumbersome hard drives and tangles of wires. Nowdays, you really can take your needs into account, when you choose a new computer.

THE NEW GENERATION

We use computers it in schools to perform mathematical operations to do some basic research, to give presentations using projectors, databases to keep records of students and teachers etc. Every school is good to have a website too because it allows teachers to publish exercises for students to complete online or can help student taking general informations from school.Teachers use projectors and interactive whiteboards to give presentations and teach sciences,history or language courses.

In banks, computers store information about the money held by each costumer and to carry out financial transactions, they enable staff to access databases.They also control the cash points or automatic teller machines.People use a card to pay for goods and services, they are asked to enter a four-digit personal identification number (PIN). In this way clients can easily pay bills and transfer money from their home.

Airline pilots use computers to help them control the plane.Monitors display data about weather conditions and fuel consumption. In airport, computers are used to regulate air traffic and to manage radar system.On the ground,airlines are connected to travel agencies by computer. Mobiles let us send texts,email people,make voice calls or download ringtones, games etc. With the camera built in it we can make video or send pictures.

Computers are also used to control the plane or in airport cintrol towers to manage radar systems and regulate air traffic. Travel agents use computers to find out about the availability of flights, prices, times,stopovers and many other details. If a travel agent lose airline ticket he is able to access through a smart phone, computer, tablet or through the information stored in the airport's database.

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