Yusuf Widiyanto's Blog

Computer security

2007-12-11T19:08:00.000-08:00

Computer Security

What is computer security?

Computer security is the process of preventing and detecting unauthorized use of your computer. Prevention measures help you to stop unauthorized users (also known as "intruders") 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.

Why should I care about computer security?

We use computers for everything from banking and investing to shopping and communicating with others through email or chat programs. Although you may not consider your communications "top secret," you probably do not want strangers reading your email, using your computer to attack other systems, sending forged email from your computer, or examining personal information stored on your computer (such as financial statements).

Who would want to break into my computer at home?

Intruders (also referred to as hackers, attackers, or crackers) may not care about your identity. Often they want to gain control of your computer so they can use it to launch attacks on other computer systems.

Having control of your computer gives them the ability to hide their true location as they launch attacks, often against high-profile computer systems such as government or financial systems. Even if you have a computer connected to the Internet only to play the latest games or to send email to friends and family, your computer may be a target.

Intruders may be able to watch all your actions on the computer, or cause damage to your computer by reformatting your hard drive or changing your data.

How easy is it to break into my computer?

Unfortunately, intruders are always discovering new vulnerabilities (informally called "holes") to exploit in computer software. The complexity of software makes it increasingly difficult to thoroughly test the security of computer systems.

When holes are discovered, computer vendors will usually develop patches to address the problem(s). However, it is up to you, the user, to obtain and install the patches, or correctly configure the software to operate more securely. Most of the incident reports of computer break-ins received at the CERT/CC could have been prevented if system administrators and users kept their computers up-to-date with patches and security fixes.

Also, some software applications have default settings that allow other users to access your computer unless you change the settings to be more secure. Examples include chat programs that let outsiders execute commands on your computer or web browsers that could allow someone to place harmful programs on your computer that run when you click on them.

ANTI VIRUS

2007-12-11T19:07:00.000-08:00

ANTI VIRUS

A recent study of 300 companies is reported to have shown that the rate of virus infection increased some 48% over a one year period, despite the fact that the companies regularly used anti-virus software. The problem? While anti-virus (AV) software was installed, it was not kept up to date regularly.

On average, the survey showed more than 86 viruses per 1,000 computers with disks brought from home as being the most popular vector. (Computer Knowledge strongly recommends that any company AV contract allow installation on both company and home computers.) Second most common vector was the e-mail attachment. Macro viruses were the most common virus type.

So, again, keep your anti-virus software updated!

History of Jakarta

2007-11-27T18:12:00.000-08:00

History of Jakarta

Jakarta, the capital of the nation, has a fascinating history. Lots of different aspects have colored the city history and the life of people today. Since the fifth century, ships from China and Champa (Vietnam), and from all islands in the archipelago docked at the mouth of the Ciliwung River. Indian and Portuguese traders also visited this small town. Javanese sailors, carrying spices from Molucca, were also docked there. Nearly all people from the East and West left their trails to blend special flavor of Jakarta. During centuries later, the city port grew into a bustling international trade center. At that time, between 17th and early 18 centuries, ships could sail further up to the river Ciliwung. Towards the south of this drawbridge, the once busy harbor town of Sunda Kelapa stretched along both sides of the river between the 12th century and 15th century.

Sunda Kalapa was the main port of the Hindu Kingdom of Sunda. The capital of the Pakuan Pajajaran kingdom was located two days journey upriver, now known as Bogor. Ships often visited this port from Palembang, Tanjungpura, Malacca, Maccasar and Madura, and even by merchants from India and South China. Sunda Kelapa exported, among other items, pepper, rice and gold.

In 1513 the first European fleet, four Portuguese ships under the command of Alvin, arrived in Sunda Kelapa from Malacca. Malacca had been conquered two years earlier by Alfonso d' Albuquerque. They were looking for spices, especially pepper, to this busy and well-organized harbor. Some years later, the Portuguese Enrique Leme visited Kalapa with presents for the King of Sunda. He was well received and on August 21, 1522 signed a treaty of friendship between the kingdom of Sunda and Portugal. The Portuguese received the right to build a go down (warehouse) and to erect a fort in Kalapa. This was regarded by the Sundanese as a consolidation of their position against the encroaching Muslim troops from the rising power of the Sultanate of Demak in Central Java.

To commemorate this treaty, they put big stone, called a Padrao, which vanished for some years. This stone was uncovered later in 1918 during an excavation for a new house in Kota area on the corner of Cengkeh Street and Nelayan Timur Street. This Padrao can now be seen in the National Museum on Medan Merdeka Barat Street. The original location of the stone suggests that the coastline in the early 16th century formed a nearly straight line, which is marked by the present of Nelayan Street, some 400 meters south to the Lookout Tower. The King of Sunda had his own reasons for great danger from the expansive Muslim Kingdom of Demak, whose troops threatened his second harbor town, Banten (west of Jakarta). Sunda felt squeezed and was in need of strong friends. Thus, the king hoped the Portuguese would return quickly and help him protect his important harbor. But they came too late. For in 1527 the Muslim leader Fatahillah appeared before Kalapa with 1,452 soldiers from Cirebon and Demak.

According to some historians, this victory of 1527 provided the reason for Fatahillah to rename Sunda Kelapa, Jayakarta, which means "Great Deed" or "Complete Victory." On the basis of this victory, Jakarta celebrates its birthday on June 22, 1527; the day Fatahillah gave the town a name of victory of over Sundanese Hindus and Portuguese sailor. Prince Jayawikarta, a follower of the Sultan of Banten, resided on the west banks of Ciliwung river, which in the early 17th century reached the roughly at our starting place, the Lookout at Pasar Ikan. He erected a military post there in order to control the mouth of the river and the Dutch who had been granted permission in 1610 to build a wooden go down and some houses just opposite there on the east bank. Dutch ships had already come to Jayakarta in 1596. The Prince tried to keep a close eye on these unruly guests.

To keep its strength equal to that of the Dutch, Prince Jayawikarta allowed the British to erect houses on the West Bank of Ciliwung River, across the Dutch go down, in 1615. The Prince granted permission to the British to erect a fort closed to his Customs Office post. Jayawikarta was in support of the British because his palace was under the threat of the Dutch cannons. In December 1618, the tense relationship between Prince Jayawikarta and the Dutch escalated. Jayawikarta soldiers besieged the Dutch fortress that covered two strong go down, namely Nassau and Mauritus. The British fleet made up of 15 ships arrived. The fleet was under the leadership of Sir Thomas Dale, former governor of the Colony of Virginia, now known as Virginia State in the United States.

The British admiral was already old and was indecisive. After the sea battle, the newly appointed Dutch governor Jan Pieter Soon Coon (1618) escaped to Molucca to seek support. Meanwhile, the commander of the Dutch army was arrested when the negotiation was underway because Jayawikarta felt that the Dutch deceived him. Then, the Prince Jayawikarta and the British entered into a friendship agreement.

The Dutch army was about to surrender to the British when in 1619, a sultan from Banten sent soldiers and summoned Prince Jayawikarta for establishing closed relationship with the British without first asking an approval from Banten authorities. The conflict between Banten and Prince Jayawikarta as well as the tensed relationship between Banten and the British had weakened the Dutch enemy. Prince Jayawikarta was moved to Tanara and died in Banten. The Dutch felt relieved and tried to establish a closer relationship with the Banten. The Dutch fortress garrison, along with hired soldiers from Japan, Germany, Scotia, Denmark, and Belgium held a party in commemoration of the change in situation. They name their fortress after Batavia to recollect the ethnic group Batavier, the Dutch ancestor. Since then Jayakarta was called Batavia for more than 300 years.

Under the relationship of J.P Coen, Dutch army attacked and destroyed the city and Jayakarta Palace on May 30, 1619. There were no remains of Jakarta except for the Padrao stone now stored at the National Museum in Jakarta. The Jayakarta grave was possibly located in Pulau Gadung. If we stand on top of Menara Syahbandar and look around, we can enjoy the beautiful panorama in the oldest area of Batavia. Certainly, we can't enjoy the remains of the city Sunda Kelapa or Jayakarta. Kasteel or the Dutch fortress, too, has been destroyed. Here we can see several remains from the mid-17th century. Nearly all of the remains are related to trade and sailing.

Syahbandar Tower was built 1839 to replace the old flagpole in ship dock located right on the side across a river. From the pole and later the tower, officials observed ships about to anchor gave signals. The tower then is used a meteorology post. To the West of the Lookout Tower, we can see the view of the present Bahari Museum. The museum represents a very old and strong edifice with Dutch architecture. The museum also provides several maps of the city, with stages of the city development shown. The museum is part of something in Dutch called Westzijdsche Pakhuizen (Warehouse on the West bank. Here nutmegs, pepper, coffee, tea, and cloth in a large scale were used to be stored.

The area around Syahbandar Tower was once the center of Kota Batavia. It was the center of a trading network with wide spread agents reaching Deshima (Nagasaki) in Japan, Surate in Persia and Cape town in South Africa. Inter-trade among Asia was more profitable than inter-trade between Asia and Europe. And the Pasar Ikan (Market Fish) once was the pulse. Here, the site where the origin of the capital of Indonesia, Jakarta, came from.

The History of Computer Programming Languages

2007-11-26T20:32:00.000-08:00

The History of Computer Programming Languages

Ever since the invention of Charles Babbage's difference engine in 1822, computers have required a means of instructing them to perform a specific task. This means is known as a programming language. Computer languages were first composed of a series of steps to wire a particular program; these morphed into a series of steps keyed into the computer and then executed; later these languages acquired advanced features such as logical branching and object orientation. The computer languages of the last fifty years have come in two stages, the first major languages and the second major languages, which are in use today.

In the beginning, Charles Babbage's difference engine could only be made to execute tasks by changing the gears which executed the calculations. Thus, the earliest form of a computer language was physical motion. Eventually, physical motion was replaced by electrical signals when the US Government built the ENIAC in 1942. It followed many of the same principles of Babbage's engine and hence, could only be "programmed" by presetting switches and rewiring the entire system for each new "program" or calculation. This process proved to be very tedious.

In 1945, John Von Neumann was working at the Institute for Advanced Study. He developed two important concepts that directly affected the path of computer programming languages. The first was known as "shared-program technique" (www.softlord.com). This technique stated that the actual computer hardware should be simple and not need to be hand-wired for each program. Instead, complex instructions should be used to control the simple hardware, allowing it to be reprogrammed much faster.

The second concept was also extremely important to the development of programming languages. Von Neumann called it "conditional control transfer" (www.softlord.com). This idea gave rise to the notion of subroutines, or small blocks of code that could be jumped to in any order, instead of a single set of chronologically ordered steps for the computer to take. The second part of the idea stated that computer code should be able to branch based on logical statements such as IF (expression) THEN, and looped such as with a FOR statement. "Conditional control transfer" gave rise to the idea of "libraries," which are blocks of code that can be reused over and over.

In 1949, a few years after Von Neumann's work, the language Short Code appeared (www.byte.com). It was the first computer language for electronic devices and it required the programmer to change its statements into 0's and 1's by hand. Still, it was the first step towards the complex languages of today. In 1951, Grace Hopper wrote the first compiler, A-0 (www.byte.com). A compiler is a program that turns the language's statements into 0's and 1's for the computer to understand. This lead to faster programming, as the programmer no longer had to do the work by hand.

In 1957, the first of the major languages appeared in the form of FORTRAN. Its name stands for FORmula TRANslating system. The language was designed at IBM for scientific computing. The components were very simple, and provided the programmer with low-level access to the computers innards. Today, this language would be considered restrictive as it only included IF, DO, and GOTO statements, but at the time, these commands were a big step forward. The basic types of data in use today got their start in FORTRAN, these included logical variables (TRUE or FALSE), and integer, real, and double-precision numbers.

Though FORTAN was good at handling numbers, it was not so good at handling input and output, which mattered most to business computing. Business computing started to take off in 1959, and because of this, COBOL was developed. It was designed from the ground up as the language for businessmen. Its only data types were numbers and strings of text. It also allowed for these to be grouped into arrays and records, so that data could be tracked and organized better. It is interesting to note that a COBOL program is built in a way similar to an essay, with four or five major sections that build into an elegant whole. COBOL statements also have a very English-like grammar, making it quite easy to learn. All of these features were designed to make it easier for the average business to learn and adopt it.

In 1958, John McCarthy of MIT created the LISt Processing (or LISP) language. It was designed for Artificial Intelligence (AI) research. Because it was designed for such a highly specialized field, its syntax has rarely been seen before or since. The most obvious difference between this language and other languages is that the basic and only type of data is the list, denoted by a sequence of items enclosed by parentheses. LISP programs themselves are written as a set of lists, so that LISP has the unique ability to modify itself, and hence grow on its own. The LISP syntax was known as "Cambridge Polish," as it was very different from standard Boolean logic (Wexelblat, 177) :

x V y - Cambridge Polish, what was used to describe the LISP program
OR(x,y) - parenthesized prefix notation, what was used in the LISP program
x OR y - standard Boolean logic

LISP remains in use today because its highly specialized and abstract nature.

The Algol language was created by a committee for scientific use in 1958. It's major contribution is being the root of the tree that has led to such languages as Pascal, C, C++, and Java. It was also the first language with a formal grammar, known as Backus-Naar Form or BNF (McGraw-Hill Encyclopedia of Science and Technology, 454). Though Algol implemented some novel concepts, such as recursive calling of functions, the next version of the language, Algol 68, became bloated and difficult to use (www.byte.com). This lead to the adoption of smaller and more compact languages, such as Pascal.

Pascal was begun in 1968 by Niklaus Wirth. Its development was mainly out of necessity for a good teaching tool. In the beginning, the language designers had no hopes for it to enjoy widespread adoption. Instead, they concentrated on developing good tools for teaching such as a debugger and editing system and support for common early microprocessor machines which were in use in teaching institutions.

Pascal was designed in a very orderly approach, it combined many of the best features of the languages in use at the time, COBOL, FORTRAN, and ALGOL. While doing so, many of the irregularities and oddball statements of these languages were cleaned up, which helped it gain users (Bergin, 100-101). The combination of features, input/output and solid mathematical features, made it a highly successful language. Pascal also improved the "pointer" data type, a very powerful feature of any language that implements it. It also added a CASE statement, that allowed instructions to to branch like a tree in such a manner:

CASE expression OF
possible-expression-value-1:
statements to execute...
possible-expression-value-2:
statements to execute...
END

Pascal also helped the development of dynamic variables, which could be created while a program was being run, through the NEW and DISPOSE commands. However, Pascal did not implement dynamic arrays, or groups of variables, which proved to be needed and led to its downfall (Bergin, 101-102). Wirth later created a successor to Pascal, Modula-2, but by the time it appeared, C was gaining popularity and users at a rapid pace.

C was developed in 1972 by Dennis Ritchie while working at Bell Labs in New Jersey. The transition in usage from the first major languages to the major languages of today occurred with the transition between Pascal and C. Its direct ancestors are B and BCPL, but its similarities to Pascal are quite obvious. All of the features of Pascal, including the new ones such as the CASE statement are available in C. C uses pointers extensively and was built to be fast and powerful at the expense of being hard to read. But because it fixed most of the mistakes Pascal had, it won over former-Pascal users quite rapidly.

Ritchie developed C for the new Unix system being created at the same time. Because of this, C and Unix go hand in hand. Unix gives C such advanced features as dynamic variables, multitasking, interrupt handling, forking, and strong, low-level, input-output. Because of this, C is very commonly used to program operating systems such as Unix, Windows, the MacOS, and Linux.

In the late 1970's and early 1980's, a new programing method was being developed. It was known as Object Oriented Programming, or OOP. Objects are pieces of data that can be packaged and manipulated by the programmer. Bjarne Stroustroup liked this method and developed extensions to C known as "C With Classes." This set of extensions developed into the full-featured language C++, which was released in 1983.

C++ was designed to organize the raw power of C using OOP, but maintain the speed of C and be able to run on many different types of computers. C++ is most often used in simulations, such as games. C++ provides an elegant way to track and manipulate hundreds of instances of people in elevators, or armies filled with different types of soldiers. It is the language of choice in today's AP Computer Science courses.

In the early 1990's, interactive TV was the technology of the future. Sun Microsystems decided that interactive TV needed a special, portable (can run on many types of machines), language. This language eventually became Java. In 1994, the Java project team changed their focus to the web, which was becoming "the cool thing" after interactive TV failed. The next year, Netscape licensed Java for use in their internet browser, Navigator. At this point, Java became the language of the future and several companies announced applications which would be written in Java, none of which came into use.

Though Java has very lofty goals and is a text-book example of a good language, it may be the "language that wasn't". It has serious optimization problems, meaning that programs written in it run very slowly. And Sun has hurt Java's acceptance by engaging in political battles over it with Microsoft. But Java may wind up as the instructional language of tomorrow as it is truly object-oriented and implements advanced techniques such as true portability of code and garbage collection.

Visual Basic is often taught as a first programming language today as it is based on the BASIC language developed in 1964 by John Kemeny and Thomas Kurtz. BASIC is a very limited language and was designed for non-computer science people. Statements are chiefly run sequentially, but program control can change based on IF..THEN, and GOSUB statements which execute a certain block of code and then return to the original point in the program's flow.

Microsoft has extended BASIC in its Visual Basic (VB) product. The heart of VB is the form, or blank window on which you drag and drop components such as menus, pictures, and slider bars. These items are known as "widgets." Widgets have properties (such as its color) and events (such as clicks and double-clicks) and are central to building any user interface today in any language. VB is most often used today to create quick and simple interfaces to other Microsoft products such as Excel and Access without needing a lot of code, though it is possible to create full applications with it.

Perl has often been described as the "duct tape of the Internet," because it is most often used as the engine for a web interface or in scripts that modify configuration files. It has very strong text matching functions which make it ideal for these tasks. Perl was developed by Larry Wall in 1987 because the Unix sed and awk tools (used for text manipulation) were no longer strong enough to support his needs. Depending on whom you ask, Perl stands for Practical Extraction and Reporting Language or Pathologically Eclectic Rubbish Lister.

Programming languages have been under development for years and will remain so for many years to come. They got their start with a list of steps to wire a computer to perform a task. These steps eventually found their way into software and began to acquire newer and better features. The first major languages were characterized by the simple fact that they were intended for one purpose and one purpose only, while the languages of today are differentiated by the way they are programmed in, as they can be used for almost any purpose. And perhaps the languages of tomorrow will be more natural with the invention of quantum and biological computers.