Computer Security Essays (1905 words) - Security, Cybercrime

Computer Security About two hundred years before, the word "computer" started to appear in the dictionary. Some people even didn't know what is a computer. However, most of the people today not just knowing what is a computer, but understand how to use a computer. Therefore, computer become more and more popular and important to our society. We can use computer everywhere and they are very useful and helpful to our life. The speed and accuracy of computer made people felt confident and reliable. Therefore, many important information or data are saved in the computer. Such as your diary, the financial situation of a oil company or some secret intelligence of the military department. A lot of important information can be found in the memory of computer. So, people may ask a question: Can we make sure that the information in the computer is safe and nobody can steal it from the memory of the computer? Physical hazard is one of the causes of destroying the data in the computer. For example, send a flood of coffee toward a personal computer. The hard disk of the computer could be endangered by the flood of coffee. Besides, human caretaker of computer system can cause as much as harm as any physical hazard. For example, a cashier in a bank can transfer some money from one of his customer's account to his own account. Nonetheless, the most dangerous thief are not those who work with computer every day, but youthful amateurs who experiment at night --- the hackers. The term "hacker "may have originated at M.I.T. as students' jargon for classmates who labored nights in the computer lab. In the beginning, hackers are not so dangerous at all. They just stole computer time from the university. However, in the early 1980s, hackers became a group of criminals who steal information from other peoples' computer. For preventing the hackers and other criminals, people need to set up a good security system to protect the data in the computer. The most important thing is that we cannot allow those hackers and criminals entering our computers. It means that we need to design a lock to lock up all our data or using identification to verify the identity of someone seeking access to our computers. The most common method to lock up the data is using a password system. Passwords are a multi-user computer system's usual first line of defense against hackers. We can use a combination of alphabetic and number characters to form our own password. The longer the password, the more possibilities a hacker's password-guessing program must work through. However it is difficult to remember a very long passwords. So people will try to write the password down and it may immediately make it a security risk. Furthermore, a high speed password-guessing program can find out a password easily. Therefore, it is not enough for a computer that just have a password system to protect its data and memory. Besides password system, a computer company may consider about the security of its information centre. In the past, people used locks and keys to limit access to secure areas. However, keys can be stolen or copied easily. Therefore, card-key are designed to prevent the situation above. Three types of card-keys are commonly used by banks, computer centers and government departments. Each of this card-keys can employ an identifying number or password that is encoded in the card itself, and all are produced by techniques beyond the reach of the average computer criminals. One of the three card-key is called watermark magnetic. It was inspired by the watermarks on paper currency. The card's magnetic strip have a 12-digit number code and it cannot be copied. It can store about two thousand bits in the magnetic strip. The other two cards have the capability of storing thousands of times of data in the magnetic strip. They are optical memory cards (OMCs) and Smart cards. Both of them are always used in the security system of computers. However, it is not enough for just using password system and card-keys to protect the memory in the computer. A computer system also need to have a restricting program to verify the identity of the users. Generally, identity can be established by something a person knows, such as a password or something a person has, such as a card-key. However, people are often forget their passwords or lose their keys. A third method must be used. It is using something a person has --- physical trait of a human being. We can use a new technology called biometric device

The Role of DNA in Evolution

The Role of DNA in Evolution Deoxyribonucleic acid (DNA) is the blueprint for all inherited characteristics in living things. It is a very long sequence, written in code, that needs to be transcribed and translated before a cell can make the proteins that are essential for life. Any sort of changes in the DNA sequence can lead to changes in those proteins, and, in turn, they can translate into changes in the traits those proteins control. Changes at a molecular level lead to microevolution of species. The Universal Genetic Code The DNA in living things is highly conserved. DNA has only four nitrogenous bases that code for all differences in living things on Earth. Adenine, cytosine, guanine, and thymine line up in a specific order and a group of three, or a codon, code for one of 20Â  amino acids found on Earth. The order of those amino acids determines what protein is made. Remarkably enough, only four nitrogenous bases that make only 20 amino acids account for all diversity of life on Earth. There has not been any other code or system found in any living (or once living) organism on Earth. Organisms from bacteria to humans to dinosaurs all have the same DNA system as a genetic code. This may point to evidence that all life evolved from a single common ancestor. Changes in DNA All cells are pretty well-equipped with a way to check a DNA sequence for mistakes before and after cell division, or mitosis. Most mutations, or changes in DNA, are caught before copies are made and those cells are destroyed. However, there are times when small changes do not make that much of a difference and will pass through the checkpoints. These mutations may add up over time and change some of the functions of that organism. If these mutations happen in somatic cells, in other words, normal adult body cells, then these changes do not affect future offspring. If the mutations happen in gametes, or sex cells, those mutations do get passed down to the next generation and may affect the function of the offspring. These gamete mutations lead to microevolution. Evidence for Evolution DNA has only come to be understood over the last century. The technology has been improving and has allowed scientists to not only map out entire genomes of many species, but they also use computers to compare those maps. By entering genetic information of different species, it is easy to see where they overlap and where there are differences. The more closely species are related on the phylogenetic tree of life, the more closely their DNA sequences will overlap. Even very distantly related species will have some degree of DNA sequence overlap. Certain proteins are needed for even the most basic processes of life, so those selected parts of the sequence that codes for those proteins will be conserved in all species on Earth. DNA Sequencing and Divergence Now that DNA fingerprinting has become easier, cost-effective, and efficient, the DNA sequences of a wide variety of species can be compared. In fact, it is possible to estimate when the two species diverged or branched off through speciation. The larger the percentage of differences in the DNA between two species, the greater the amount of time the two species have been separate. These molecular clocks can be used to help fill in the gaps of the fossil record. Even if there are missing links within the timeline of history on Earth, the DNA evidence can give clues as to what happened during those time periods. While random mutation events may throw off the molecular clock data at some points, it is still a pretty accurate measure of when species diverged and became new species.