Computer security requirements and Attacks

Computer and network security address four requirements:

1. confidentiality: Requires that data only be accessible by authorized parties. This types of access includes printing, displaying and other forms of disclosure of the data.

2. Integrity: Requires that data can be modified only by authorized users. Modification includes writing, changing, changing status, deleting and creating.

3. Availability: Requires that data are available to authorized parties.

4. Authenticity: Requires that host or service be able to verify the identity of a user.

Types of Network Attacks

There are four primary classes of attacks.

1. Reconnaissance : Reconnaissance is the unauthorized discovery and mapping of systems, services, or vulnerabilities. It is also known as information gathering and, in most cases, it precedes another type of attack. Reconnaissance is similar to a thief casing a neighborhood for vulnerable homes to break into, such as an unoccupied residence, easy-to-open doors, or open windows.

2. Access : System access is the ability for an intruder to gain access to a device for which the intruder does not have an account or a password. Entering or accessing systems usually involves running a hack, script, or tool that exploits a known vulnerability of the system or application being attacked.

3. Denial of Service : Denial of service (DoS) is when an attacker disables or corrupts networks, systems, or services with the intent to deny services to intended users. DoS attacks involve either crashing the system or slowing it down to the point that it is unusable. But DoS can also be as simple as deleting or corrupting information. In most cases, performing the attack involves simply running a hack or script. For these reasons, DoS attacks are the most feared.

4. Worms, Viruses, and Trojan Horses : Malicious software can be inserted onto a hos to damage or corrupt a system, replicate itself, or deny access to networks, systems, or services. Common names for this type of software are worms, viruses, and Trojan horses.

Error Control

When data is transmitted over a cable or channel, there is always a chance that some of the bits will be changed (corrupted) due to noise, signal distortion or attenuation. If errors do occur, then some of the bits will either change from 0 to 1 or from 1 to 0. Error Control allows the receiver to inform the sender of any frames lost or damaged in transmission and coordinates the retransmission of those frames by the sender. Error control is divided in two main categories:

Error Detection It allows a receiver to check whether received data has been corrupted during transmission. It can, for example, request a retransmission. Error Correction This type of error control allows a receiver to reconstruct the original information when it has been corrupted during transmission. In the data link layer, the term error control refers primarily to methods of error detection and retransmission. Error control in the data link layer is often implemented simply: Any time an error is detected in an exchange, specified frames are retransmitted. This process is called automatic repeat request (ARQ). Error control in the data link layer is based on automatic repeat request, which is the retransmission of data.

There are 2 ways to correct found errors: • Forward error correction (FEC is accomplished by adding redundancy to the transmitted information using a predetermined algorithm. Each redundant bit is invariably a complex function of many original information bits. The original information may or may not appear in the encoded output; codes that include the unmodified input in the output are systematic, while those that do not are nonsystematic.) and • Automatic repeat request (ARQ) ( in which the receiver detects transmission errors in a message and automatically requests a retransmission from the transmitter. Usually, when the transmitter receives the ARQ, the transmitter retransmits the message until it is either correctly received or the error persists beyond a predetermined number of retransmissions.A few types of ARQ protocols are Stop-and-wait ARQ, Go-Back-N ARQ and Selective Repeat ARQ.).

Seven Layers of OSI Reference Model

1. Physical Layer:

physical layer is the bottom layer of the OSI reference model. The physical layer has four improtant characteristics. Mechanical. Relates to the physical properties of the interface to a transmission medium. Typically, the specification is of a pluggable connector that joins one or more signal conductors, called circuits.

Electrical. Relates to the representation of bits (e.g., in terms of voltage levels) and the data transmission rate of bits. It defines the voltage, current, modulation, bit synchronization, connection activation and deactivation, and various electrical characteristics for the transmission media (such as unshielded or shielded twisted-pair cabling, coaxial cabling, and fiber-optic cabling). Functional. Specifies the functions performed by individual circuits of the physical interface between a system and the transmission medium. Procedural. Specifies the sequence of events by which bit streams are exchanged across the physical medium.

2. Data Link Layer:

The physical layer provides only a raw bit-stream service, the data link layer attempts to make the physical link reliable while providing the means to activate, maintain, and deactivate the link . For LANs, the Project 802 standards of the Institute of Electrical and Electronics Engineers (IEEE) separate the data-link layer into two sublayers:

• The logical link control (LLC) layer, the upper of the two layers, which is responsible for flow control, error correction, and resequencing functions for connection-oriented communication, but which also supports connectionless communication • The media access control (MAC) layer, the lower of the two layers, which is responsible for providing a method for stations to gain access to the medium Functions:

Framing. The data link layer divides the stream of bits received from the network layer into manageable data units called frames. Physical addressing. If frames are to be distributed to different systems on the network, the data link layer adds a header to the frame to define the sender and/or receiver of the frame. If the frame is intended for a system outside the sender's network, the receiver address is the address of the device that connects the network to the next one. Flow control. If the rate at which the data are absorbed by the receiver is less than the rate at which data are produced in the sender, the data link layer imposes a flow control mechanism to avoid overwhelming the receiver. Error control. The data link layer adds reliability to the physical layer by adding mechanisms to detect and retransmit damaged or lost frames. It also uses a mechanism to recognize duplicate frames. Error control is normally achieved through a trailer added to the end of the frame. Access control. When two or more devices are connected to the same link, data link layer protocols are necessary to determine which device has control over the link at any given time Examples of data-link protocols for local area networking include the following: • IEEE 802.3, which provides the Carrier Sense Multiple Access with Collision Detection (CSMA/CD) access method for baseband Ethernet networks • IEEE 802.5, which provides the token-passing access method for baseband token ring implementations For WANs, data-link layer protocols encapsulate LAN traffic into frames suitable for transmission over WAN links. Common data-link encapsulation methods for WAN transmission include the following: • Point-to-point technologies such as Point-to-Point Protocol (PPP) and High-level Data Link Control (HDLC) protocol • Multipoint technologies such as frame relay, Asynchronous Transfer Mode (ATM), Switched Multimegabit Data Services (SMDS), and X.25

3. Network Layer:

Layer 3 of the Open Systems Interconnection (OSI) reference model for networking. The network layer is responsible for functions such as the following: • Logical addressing and routing of packets over the network • Establishing and releasing connections and paths between two nodes on a network • Transferring data, generating and confirming receipts, and resetting connections The network layer also supplies connectionless and connection-oriented services to the transport layer above it. The network layer functions closely with the physical layer (layer 1) and data-link layer (layer 2) in most realworld network protocol implementations. On TCP/IP-based networks, IP addresses and network numbers are used at the network layer, and IP routers perform their routing functions at this layer. An example of an OSI model network layer protocol is the X.25 packet-switching network layer protocol, which is built on the X.21 physical layer protocol.

4. Transport Layer:

Layer 4 of the Open Systems Interconnection (OSI) reference model. The transport layer is responsible for providing reliable transport services to the upper-layer protocols. These services include the following: • Flow control to ensure that the transmitting device does not send more data than the receiving device can handle. • Packet sequencing for segmentation of data packets and remote reassembly. • Error handling and acknowledgments to ensure that data is retransmitted when required. • Multiplexing for combining data from several sources for transmission over one data path. • Virtual circuits for establishing sessions between communicating stations. The Transmission Control Protocol (TCP) of the TCP/IP protocol suite resides at the transport layer. A connection between two devices that acts as though it's a direct connection even though it may physically be circuitous. The term is used most frequently to describe connections between two hosts in a packet-switching network. In this case, the two hosts can communicate as though they have a dedicated connection even though the packets might actually travel very different routes before arriving at their destination. An X.25 connection is an example of a virtual circuit. Virtual circuits can be either permanent (called PVCs) or temporary (called SVCs).

5. Session Layer:

Layer 5 of the Open Systems Interconnection (OSI) reference model, which enables sessions between computers on a network to be established and terminated. The session layer does not concern itself with issues such as the reliability and efficiency of data transfer between stations because these functions are provided by the first four layers of the OSI reference model. Functions: Dialog control: The session layer allows two systems to enter into a dialog. It allows the communication between two processes to take place in either half- duplex (one way at a time) or full-duplex (two ways at a time) mode. Synchronization: The session layer allows a process to add checkpoints, or synchronization points, to a stream of data. For example, if a system is sending a file of 2000 pages, it is advisable to insert checkpoints after every 100 pages to ensure that each 100-page unit is received and acknowledged independently. In this case, if a crash happens during the transmission of page 523, the only pages that need to be resent after system recovery are pages 501 to 523. Pages previous to 501 need not be resent.

6. Presentation Layer:

The presentation layer is concerned with the syntax and semantics of the information exchanged between two systems . Specific responsibilities of the presentation layer include the following: Translation. The processes (running programs) in two systems are usually exchanging information in the form of character strings, numbers, and so on. The information must be changed to bit streams before being transmitted. Because different computers use different encoding systems, the presentation layer is responsible for interoperability between these different encoding methods. The presentation layer at the sender changes the information from its sender-dependent format into a common format. The presentation layer at the receiving machine changes the common format into its receiver-dependent format. Encryption. To carry sensitive information, a system must be able to ensure privacy. Encryption means that the sender transforms the original information to another form and sends the resulting message out over the network. Decryption reverses the original process to transform the message back to its original form. Compression. Data compression reduces the number of bits contained in the information. Data compression becomes particularly important in the transmission of multimedia such as text, audio, and video.

7. Application layer:

Layer 7 of the Open Systems Interconnection (OSI) reference model, in which network-aware, user-controlled software is implemented—for example, e-mail, file transfer utilities, and terminal access. The application layer represents the window between the user and the network. Examples of protocols that run at the application layer include File Transfer Protocol (FTP), Hypertext Transfer Protocol (HTTP), telnet, and similar protocols that can be implemented as utilities the user can interface with. File transfer, access, and management. This application allows a user to access files in a remote host (to make changes or read data), to retrieve files from a remote computer for use in the local computer, and to manage or control files in a remote computer locally. Mail services. This application provides the basis for e-mail forwarding and storage. Directory services. This application provides distributed database sources and access for global information about various objects and services.

History of Computer Networks

Prior to the introduction of personal computers, businesses utilized minicomputers for local computers, with users connected to the minicomputer remotely via terminals. The minicomputers were often connected via computer networks to enable distributed systems–software made up of components, located or distributed on the network computers, which communicate via messages to achieve a common purpose.

As the speed and storage capacity of personal computers increased, as their cost decreased, and as Apple and Windows operating systems developed, the personal computer replaced the minicomputer for local and network computing.

The networks which began as local hard-wired networks grew rapidly by utilizing telephone networks and eventually evolved to include wireless connections. Thus, local computing grew to become wide area computing, and today, the network has expanded to include the entire Internet.

Privacy

Privacy:

Privacy is the right of individual to hold back certain information about self without disclosure and allow it to be collected with the consent (agreement) with the assurance that it would remain protected from unauthorized access.

Key elements of effective privacy

• Understand your company’s compliance (obedience to rule) and culture • Align and train management and staff on security practices • Know your data, where it is, and what must be protected • Ensure third parties comply (obey rule) with your privacy policies • Understand your threats and controls • Test and update controls regularly • Be prepared to respond to incidents

PRIVACY RISKS

Privacy risk is defined as the “potential loss of control over personal information”. Although an individual may consent (agree) to the use of his or her personal information, the “loss of control” occurs when the organization fails to provide adequate safeguards. A privacy risk includes any potential problems involving the collection, use, or disclosure of personal data.

There are several types of privacy risk:

• Legal Compliance—Failure to comply with privacy laws and regulations can result in significant legal sanctions, liability (financial law), fines, and other unpleasant consequences. • Reputational—Having a privacy mishap can severely damage the reputation. • Financial—Privacy violations can lead to costly litigation (process of bringing before a law court), large damage awards, and expensive and burdensome legal requirements (data security breach (failure to do what is required by law)notification). • Employee Well-Being—Privacy mishaps can affect and harm employees • Soured Relationships—Privacy mishaps or even poor privacy practices that have not involved an actual mishap can sour relationships between schools and parents, applicants, donors, alumni (former students), and others. • Time and Resources—One of the largest often under-appreciated privacy risks involves the extensive amount of time and resources needed to respond to a privacy mishap.

Government Information: The benefits of data sharing do not solely accrue (to increase) to the governments or organizations that collect, use and disclose the information. There are definitely benefits to the citizenry. Anyone who has ever changed provinces with children in school and elderly parents in need of healthcare would fight for one-stop shopping, and single source address change. Other potential benefits include: convenience for the citizen; better program delivery through a comprehensive or clustered approach; automatic entitlement to programs; better risk management and cost control; efficiency through more effective use of data; and better information dissemination and training.

Risks of Data Centralization, Distributed Shared Access, and Data Mining

• use of data for purposes unrelated to the purpose for which the data was collected; • loss of control of data by agencies; • inability to correct errors as data travels; • outdated/incomplete records (e.g., criminal history records without dispositions); • conflicting time periods resulting in incorrect linkages and inferences (conclusion); • decisions made using unrelated, inaccurate data without the knowledge of the citizen; • hostile users (i.e., the citizen may not know which organization ultimately holds and uses the data, and there may be no trust relationship); • profiling and the possibility of discrimination (e.g., potential Canadian Charter of Rights and Freedoms issues); • lack of accountability; • absence of enforceable rights (e.g., due process); • legal complexity because of sharing among federal/provincial/territorial (FPT) agencies; and • the consequences of greater transparency.

Consumer privacy (customer privacy) Consumer privacy, also known as customer privacy, involves the handling and protection of sensitive personal information that individuals provide in the course of everyday transactions. This involves the exchange or use of data electronically or by any other means, including telephone, fax, written correspondence, and even direct word of mouth.

Databases and Personal Records:

• When information is stored in a computer, there is little incentive (a thing that encourages sb to do sth) to get rid of it; hence, information may stay with an individual permanently. Information stored in a computer takes up very little space and is easy to maintain and transfer. • When he was ten years old may easily follow him through life because the information has been recorded once and there is little motivation to delete it. Because it is so easy to keep information, some fear that individuals will become categorized at early stages in their lives. • One way to see this is to imagine what it would be like elementary and secondary school records were put into a national database where prospective employers, government agencies, or insurance companies could get access. We might find decision being made about us on the basis of testing done when we were in elementary school or on the basis of disciplinary incidents in our teenage years. • While record-keeping is by no means a new activity, it appears that computers have changed record-keeping activities in the following ways:

1. They have made possible a new scale of information gathering, 2. They have made possible new kinds of information, 3. They have made possible a new scale of information distribution, 4. The effect of erroneous information can be magnified, and 5. Information about events in one’s life may stay in one’s records for life.

Email privacy

Email privacy is the broad topic dealing with issues of unauthorized access and inspection of electronic mail. This unauthorized access can happen while an email is in transit, as well as when it is stored on email servers or on a user computer. Email has to go through potentially entrusted intermediate computers (email servers, ISPs) before reaching its destination, and there is no way to tell if it was accessed by an unauthorized entity. This is different from a letter sealed in an envelope, where by close inspection of the envelope, it might be possible to tell if someone opened it. In that sense, an email is much like a postcard whose contents are visible to everyone who handles it. Emails are stored at multiple locations: on the sender's computer, your Internet Service Provider's (ISP) server, and on the receiver's computer. Deleting an email from your inbox doesn't mean there aren't multiple other copies still out there. Emails are also vastly easier for employers and law enforcement to access than phone records. Finally, due to their digital nature, they can be stored for very long periods of time, so think twice before writing something down in an email you don't want others to see. How to Keep Your Email Private First, to maintain your expectation to privacy in the first place, always use password-protected computers and email clients. After that, there's really only one way to ensure that your emails are kept confidential -- encrypt them. The two most popular forms of email encryption are OpenPGP and S/MIME. Encryption scrambles your email into something unintelligible that only someone who has the correct digital "key" can read. Due to speed and convenience issues, however, few people use encryption and most email remains unencrypted and unsecure. The best advice is to treat every email as though it were open to the public to read. Don't say things you don't want others to read, and remember that even after you've deleted your emails, they will be available for years from other sources.

Web Privacy:

• A privacy policy is a document telling visitors to your site what information you collect and what you do with that information. Very simply: it is a short explanation of what you are doing to observe visitors to your website.

Two good reasons to develop a privacy policy 1. Create a better electronic environment on the internet 2. Laws / legislation may pertain (to be relevant to sth) to your business By letting people know what info is collected and what is done with that information, you can create a transparent environment in which people / consumers are more confident. You can eliminate stress and concerns about abuse (to make bad use of sth) of personal info. Various legislations and legal guidelines, for example in the US and in the UK, are being developed and may affect your website, depending on what information you collect, how you do it, and what you do with it. The European Union has developed similar guidelines that contain a bit too much legal rhetoric (the art of using language in an impressive way) to be completely useful. • Your policy should be written in plain readable language. Consider the policy to be a part of your site. Design the policy and publish it like the rest of your site. Design it as if you actually want people to read it. Make it short, friendly & intuitive. It should be easily accessible throughout your site. • When you visit our site, the pages that you look at, and a short text file called a cookie, are downloaded to your computer. A cookie is used to store small amounts of information. This information is collected for traffic analysis only. The cookie does not contain personal details. Depending on the browser that you use, you can set your preferences to block/ refuse cookies, and/ or notify you before they are placed. • There is an important distinction to be made here between cookies and spyware. Spyware collects information about your surfing habits across the internet and sends this information out from your computer. Cookies collect information about your surfing habits only on the site of the provider of the cookie, in other words just on one site.

Protecting privacy Your privacy on the Internet depends on your ability to control both the amount of personal information that you provide and who has access to that information. To read about how your information gets on the Internet and how it is used, see Your information on the Internet: What you need to know. Follow the practical advice below to help increase your privacy online. Think before you share personal information First, read the website's privacy policy Privacy policies should clearly explain what data the website gathers about you, how it is used, shared, and secured, and how you can edit or delete it. (For example, look at the bottom of this and every page on Microsoft.com.) No privacy statement? Take your business elsewhere.

Do not share more than you need to • Do not post anything online that you would not want made public. • Minimize details that identify you or your whereabouts. • Keep your account numbers, user names, and passwords secret. • Only share your primary email address or Instant Message (IM) name with people who you know or with reputable organizations. Avoid listing your address or name on Internet directories and job-posting sites. • Enter only required information—often marked with an asterisk (*)—on registration and other forms. Choose how private you want your profile or blog to be Modify Internet Explorer or website settings or options to manage who can see your online profile or photos, how people can search for you, who can make comments on what you post, and how to block unwanted access by others. Offensive Speech and Censorship in Cyberspace

What is there? What is illegal?

• What is offensive (very unpleasant) speech? What should be prohibited or restricted by law in cyberspace? • State of Georgia tried to ban pictures of marijuana (form of the drug, usu smoked for pleasure) from the internet • Pornography, Playboy, read about sex or how to make bombs, make photo copies and send them by mail without return address.

What was really illegal?

Obscene (disgusting by accepted moral standards, esp in sexual matters) material is not protected by the First Amendment. The criteria are that:

(1) it depicts sexual (or excretory) acts whose depiction is specifically prohibited by state law, (2) it depicts these acts in a patently (clearly) offensive manner, appealing to prurient (having or showing excessive interest in sexual matters) interest as judged by a reasonable person using community standards and (3) it has no serious literary, artistic, social political, or scientific value. - The second point – the application of community standards – was compromise intended to avoid the problem…

In 1996, Congress passed Child Pornography Prevention Act to extend ... to include “virtual” Children,

Material inappropriate for children – pornography can be regulated and banned, but only for minors – technology changes the context » on the Web, children have access to the same ‘adult’ text, images, videos, etc. as adults. » online proprietors don’t know the customer is not an adult. – protecting children » regardless of the medium: it is illegal to create, possess or distribute child pornography. it is illegal to lure (to attract a person) children into sexual activity.

Censorship Laws – Communications Decency Act (CDA, 1996) » publicity and public pressure lead Congress to pass this act. » anyone who made available to anyone under 18 any communication that is obscene or indecent would be subject to a $250,000 fine and two years in prison. » In 1997, the CDA was ruled unconstitutional because it was too vague and too broad in protecting children online and because less restrictive means are available [ACLU v. Reno (Feb 1996)] – Child Online Protection Act (COPA, 1998) » commercial Web sites that make available to minors materials “harmful to minors”, as judged by community standards would be subject to a $50,000 fine and six months in jail » used Miller v. California (1973) definition of obscene » In 2000 and 2003, COPA was ruled unconstitutional by a federal court (definition of obscene speech still to broad) » In 2004, COPA was ruled unconstitutional by the Supreme Court

Censorship Laws (cont’d) – Children’s Internet Protection Act (CHIPA, 2000) » any school or library receiving federal Internet funds must install filtering software on all Internet terminals » filters must block sites containing child pornography, obscene material, and any material deemed “harmful to minors” » A federal appeals court ruled a major part of CHIPA unconstitutional in 2002 but the Supreme Court upheld the law in 2003

Limiting Internet Access in Libraries and Schools – Filtering Software » Benefits: prevent access to inappropriate material on the Internet by screening words or phrases, blocking sites according to rating system, or disallowing access to specific sites in a list. » Problems: can be ineffective—kids get around the filters; the words, phrases, rating systems, etc. are subjective (based on personal taste); “banned” keywords can be overly restrictive for adult users and for legitimate (reasonable) use by minors, not transparent

Types of filtering – URL filtering – keyword filtering – dynamic content filtering Popular Filters – ConnectProtect, CYBERsitter, CyberPatrol

Anonymity Anonymity, adjective "anonymous", is derived from the Greek word ἀνωνυμία, anonymia, meaning "without a name" or "namelessness". In colloquial (used in normal conversation but not formal speech) use, "anonymous" is used to describe situations where the acting person's name is unknown. The important idea here is that a person be non-identifiable, unreachable, or untraceable. Anonymity is seen as a technique, or a way of realizing, certain other values, such as privacy, or liberty. The internet community is quickly changing and evolving as more of the world comes on-line. Free speech and anonymity have always been important real-world societal issues and have been the topics of numerous heated court cases. These issues are becoming increasingly important as more people discover the digital world and find the need for anonymity in this new society.

Individuals sometimes choose to remain anonymous to safeguard their privacy, for example, when browsing in a department store or purchasing an "adult" magazine. Browsing the Web has also, to date, usually been an anonymous activity. Moving beyond the Web to the Internet in general, one can send anonymous messages using an anonymous remailer program. It is fairly easy today for a technically sophisticated person to remain anonymous and avoid accountability on the Internet for actions which are questionable or illegal, e.g., sending advertising mail to numerous newsgroups (spamming), running a pornography server, or hacking the Web page of another person.

Computer Crime

Cyber crime, e-crime, electronic crime, or hi-tech crime. Computer crime is an act performed by a knowledgeable computer user, sometimes referred to as a hacker that illegally browses or steals a company's or individual's private information. In some cases, this person or group of individuals may be malicious (intended to harm sb) and destroy or otherwise corrupt the computer or data files.

Computer crimes are criminal activities which involve the use of information technology to gain an illegal or unauthorized access to a computer system with the intent of damaging, deleting, or altering computer data.

Examples of computer crimes

1. Child pornography - Making or distributing child pornography. 2. Cyber terrorism - Hacking, threats, and blackmailing towards a business or person. 3. Cyberbully or Cyberstalking - Harassing others online. 4. Creating Malware - Writing, creating, or distributing malware (e.g. viruses and spyware.) 5. Denial of Service attack - Overloading a system with so many requests it cannot serve normal requests. 6. Fraud - Manipulating data, e.g. changing banking records to transfer money to an account. 7. Harvesting - Collect account or other account related information on other people. 8. Identity theft - Pretending to be someone you are not. 9. Intellectual property theft - Stealing another persons or companies intellectual property. 10. Phishing - Deceiving individuals to gain private or personal information about that person. 11. Salami slicing - Stealing tiny amounts of money from each transaction. 12. Spamming - Distributed unsolicited e-mail to dozens or hundreds of different addresses. 13. Spoofing - Deceiving a system into thinking you are someone you really are not. 14. Unauthorized access - Gaining access to systems you have no permission to access. 15. Wiretapping - Connecting a device to a phone line to listen to conversations.

Prehistory of Computing

The earliest known tool for use in computation was the abacus, and it was thought to have been invented in Babylon circa 2400 BC. Its original style of uses was by lines drawn in sand with pebbles. Abaci, of a more modern design, are still used as calculation tools today. This was the first computer and most advanced system of calculation known to date.

In 1110 BC, the south pointing chariot was invented in ancient China. It was the first known geared mechanism to use a differential gear, which was later used in analog computers. The Chinese also invented a more sophisticated abacus from around the 2nd century BC known as the Chinese abacus.

In the fifth century BC in ancient India, the grammarian Panini formulated the grammar of Sanskrit known as the Ashtadhyayi which was highly systematized and technical.

In the 3rd century BC, Archimedes used the mechanical principle of balance to calculate mathematical problems, such as the number of grains of sand in the universe, which also require a recursive notation for numbers.

The Antikthera mechanism is believed to be the earliest known mechanical analog computer. It was designed to calculate astronomical positions.

Mechanical analog computer devices appeared again a thousand years later in the medieval Islamic world and were developed by Muslim astronomers.

During the middle ages, several European philosophers made attempts to produce analog computer devices. Influenced by the Arabs and Scholasticism, philosopher Ramon Llull (1232 to 1314) devoted a great part of his life to defining and designing several logical machines that, by combining simple and undeniable philosophical truths, could produce all possible knowledge.

Indeed, when John Napier discovered logarithms for computational purposes in the early 17th century, there followed a period of considerable progress by inventors and scientists in making calculating tools. The apex of this early era of formal computing can be seen in the difference engine and its successor the analytical engine, both by Charles Babbage.

Lumbini (Birth Place Of Lord Buddha)

Lumbini that means 'The Lovely One' in Sanskrit is a famous Buddhist site in the Lumbini District Zone of Nepal. Lumbini is considered the birthplace of Gautam Buddha. Many a times referred as 'The Light of Asia', Buddha was the founder of Buddhism faith. His period is estimated to be approximately between 563 and 483 BC.

Lumbini is located 25kms east of the municipality of Kapilvastu. Kapilvastu was the seat of governance of the then kingdom of Nepal. In the year 1896, the Indo-British archaeology team discovered a great stone pillar at the site. Later that pillar was attributed to Ashoka, the Mauryan ruler and propagator of Buddhism. The records maintained by Fa Hein were also taken in to consideration in the process. For Buddhists, this is one of four pilgrimage sites based around the life of Gautam Buddha, the other three being Kushinagar, Bodh Gaya, and Sarnath. Going by its cultural, religious and historical importance, UNESCO declared Lumbini, a world heritage site in the year 1997.

The place is famous for Maya Devi temple. It is believed that the present temple has been built at the place where Queen Maya gave birth to lord Buddha. Another important structure is the Ashoka pillar. Apart from that Lumbini has ruins of various Stupas and monasteries. Then there is Pushkarni pond where Queen Maya took bath before giving birth to Buddha.

The Lumbini region comes under Lumbini Trust, an NGO. Foreign pilgrims here have constructed new temples and monasteries. The Buddhist associations of China, Myanmar and Gautami Nuns have their separate pagodas. The ones by Japan, Sri Lanka and Vietnam are under construction.

Nepal

Nepal is in Southern Asia, between China and India. It covers total area of 143,351 sq km and its boundary is 2,926 km long in total, bordered by China 1,236 km and India 1,690 km. It is a landlocked country.

The weather and climate varies from hot summers to severe winters. Nepal has varieties of lands as it has weather and people. The land starts from 70m from sea level from Kanchan Kalan in Terai and passes though hilly region to the world's highest point Mount Everest at 8,848 m

Nepal is home to the Himalayan Mountains. For thousands of years people have traveled to the Himalayas seeking spiritual enlightenment, proclaiming man could be freed of all sin by merely gazing upon their peaks. This tradition is continued today by pilgrims who journey to Nepal across the globe to glimpse upon its natural beauty and explore its ancient history. But there's another side to Nepal. A side few travelers ever witness. Poverty-stricken slums and villages have become a common sight across the landscape.

Nepal is known for its natural beauty and it has its own cultures. It has more than 70 ethnic groups and more than 60 different languages are spoken in different parts of Nepal. Nepali is the national language of Nepal. People practice several religion. Till now Hinduism and Buddhism have the largest population.

Kathmandu is the capital, and Nepal has 30 millions people.

Top Programming Languages For Jobs In 2016

1. JavaScript

JavaScript is a lightweight, interpreted programming language. It is designed for creating network-centric applications. It is complimentary to and integrated with Java. JavaScript is very easy to implement because it is integrated with HTML. It is open and cross-platform.

2. Java

Java is a high-level programming language originally developed by Sun Microsystems and released in 1995. Java runs on a variety of platforms, such as Windows, Mac OS, and the various versions of UNIX. This tutorial gives a complete understanding of Java.

3. Python

Python is an easy to learn, powerful programming language. It has efficient high-level data structures and a simple but effective approach to object-oriented programming. Python’s elegant syntax and dynamic typing, together with its interpreted nature, make it an ideal language for scripting and rapid application development in many areas on most platforms.

4. C

C is a general-purpose, procedural, imperative computer programming language developed in 1972 by Dennis M. Ritchie at the Bell Telephone Laboratories to develop the UNIX operating system.

5. C#

This general-purpose language was originally designed by Microsoft to be used for developing apps on the Microsoft platform, and C# developers love the language for being pleasant to use and well-designed. If you want to build apps for the Microsoft platform.

6. Ruby

A dynamic, open source programming language with a focus on simplicity and productivity. It has an elegant syntax that is natural to read and easy to write.

7. PHP

PHP is a server scripting language, and a powerful tool for making dynamic and interactive Web pages.PHP is a widely-used, free, and efficient alternative to competitors such as Microsoft's ASP.

8. Swift

Swift is a powerful and intuitive programming language for macOS, iOS, watchOS and tvOS. Writing Swift code is interactive and fun, the syntax is concise yet expressive, and Swift includes modern features developers love. Swift code is safe by design, yet also produces software that runs lightning-fast.

9. C++

C++ is an object oriented programming (OOP) language, developed by Bjarne Stroustrup, and is an extension of C language. It is therefore possible to code C++ in a "C style" or "object-oriented style." In certain scenarios, it can be coded in either way and is thus an effective example of a hybrid language.

10. Perl

Perl is a script programming language that is similar in syntax to the C language and that includes a number of popular UNIX facilities such as sed, awk, and tr. Perlis an interpreted language that can optionally be compiled just before execution into either C code or cross-platform bytecode.

10 Common Interview Question

1. Tell me about yourself.

2. Why should we hire you.

3. Talk about your strengths.

4. Are you planning for future studies.

5. What do you know about our company.

6. What are your weaknesses?

7. Where do you see yourself in five years?

8. How well do you handle change?

9. Do you work well under pressure?

10. How do you make important decisions?

Unix/Linux File Commands

ls – directory listing
ls -al – formatted listing with hidden files
cd dir - change directory to dir
cd – change to home
pwd – show current directory
mkdir dir – create a directory dir
rm file – delete file
rm -r dir – delete directory dir
rm -f file – force remove file
rm -rf dir – force remove directory dir *
cp file1 file2 – copy file1 to file2
cp -r dir1 dir2 – copy dir1 to dir2; create dir2 if it
doesn't exist
mv file1 file2 – rename or move file1 to file2
if file2 is an existing directory, moves file1 into
directory file2
ln -s file link – create symbolic link link to file
touch file – create or update file
cat > file – places standard input into file
more file – output the contents of file
head file – output the first 10 lines of file
tail file – output the last 10 lines of file
tail -f file – output the contents of file as it
grows, starting with the last 10 lines

Drop Database using PHP Script

PHP uses mysql_query function to create or delete a MySQL database. This function takes two parameters and returns TRUE on success or FALSE on failure.

Create Database in Mysql Server using PHP Script

PHP uses mysql_query function to create or delete a MySQL database. This function takes two parameters and returns TRUE on success or FALSE on failure.

MySQL Connection using PHP Script

PHP provides mysql_connect() function to open a database connection.This function takes five parameters and returns a MySQL link identifier on success or FALSE on failure.

You can disconnect from MySQL database anytime using another PHP function mysql_close(). This function takes a single parameter, which is a connection returned by mysql_connect() function.

Comment

This construct encloses text comments that will not be displayed by the browser. It may be used for informational messages for developers.

HTML5

HTML5 is meant to represent a new version of HTML along the HTML 4 path. HTML document is simply a text file that contains the information you want to publish and the appropriate markup instructions indicating how the browser should structure or present the document.

abbr (Abbreviation)

This element allows authors to clearly indicate a sequence of characters that defines an abbreviation for a word (such as Mr. instead of Mister, or Btl instead of Butwal).

a (Anchor)

This element defines a hyperlink, the named target destination for a hyperlink, or both.

H1 to H6 tags (How To Make Headings)

These tags implement six levels of document headings, h1 is the most prominent and h6 is the least prominent.

Image Tag (How To Insert Image)

This element is used to add images in a html

Examples