Attacks Used to Hack Email Accounts and Their Preventive Measures Essay Example

Attacks Used to Hack Email Accounts and Their Preventive Measures Essay The present-day network threat scenario is unprecedented in both scale and impact. CYBER CRIMINALS has become increasingly confident in their own abilities because of good organization skills and years of experience in evading law enforcement. Armed with sophisticated technical knowledge, a whole bunch of tools and operating systems with exploits, their sole objective today is to cause irreparable damage to the security and business interests of organizations. The biggest â€Å"brand name† between all terrorist groups across the world The Al-Qaeda†, Islamic militant group â€Å"Tehrik-I-Taliban Pakistan† and many more terrorist organizations perform cyber terrorism i. e. , disrupt attacks against information systems for the primary purpose of stealing confidential information regarding the nation’s security issues and secondary purpose is creating alarm and panic among the cyber army of the nation. This can include use of information technology to organize and execute attacks against networks, computer systems and telecommunications infrastructures, or for exchanging information or making threats electronically. Therefore there is a huge requirement for each and every one of us to know the minimum preventive measures so as to avoid the exploitation of a hacker as he may use our computer as a shield to hide his identity. Our paper discusses on the types on hackers and the main motto behind these people performing these attacks in an attempt to compromise any computer system. Our paper emphasizes on various methods by which passwords can be stolen and then used for personal purpose. A live performance on how an account can be hacked (say facebook) will be demonstrated by using the phishing attack. We will write a custom essay sample on Attacks Used to Hack Email Accounts and Their Preventive Measures specifically for you for only $16.38 $13.9/page Order now We will write a custom essay sample on Attacks Used to Hack Email Accounts and Their Preventive Measures specifically for you FOR ONLY $16.38 $13.9/page Hire Writer We will write a custom essay sample on Attacks Used to Hack Email Accounts and Their Preventive Measures specifically for you FOR ONLY $16.38 $13.9/page Hire Writer All the preventive measures that needs to be taken to overcomes these problems and stay safe from this cyber world attackers will be briefly explained so as to make everyone technically strong and preventing their computers getting exploited†¦ Let’s build a stronger nation†¦. JAI HIND†¦ Vamshi Krishna Gudipati A. K. A h4x0r le610n, 4th year b. tech, COMPUTER SCIENCE AND ENGINEERING, WARANGAL INSTITUTE OF TECHNOLOGY AND SCIENCE. Information security  means protecting information and  information systems  from unauthorized access, use, disclosure, disruption, modification, perusal, inspection, recording or destruction. The terms information security,  computer security  and  information assurance  are frequently used interchangeably. These fields are interrelated often and share the common goals of protecting the  confidentiality,  integrity  and  availability  of information; however, there are some subtle differences between them. These differences lie primarily in the approach to the subject, the methodologies used, and the areas of concentration. Information security is concerned with the confidentiality, integrity and availability of  data  regardless of the form the data may take: electronic, print, or other forms. Computer security can focus on ensuring the availability and correct operation of a  computer system  without concern for the information stored or processed by the computer. Information assurance focuses on the reasons for assurance that information is protected, and is thus reasoning about information security. Governments,  military,  corporations ,  hospitals, and private  businesses  amass a great deal of confidential information about their employees, customers, products, research, and financial status. Most of this information is now collected, processed and stored on electronic  computers  and transmitted across  networks  to other computers. WHAT IS HACKING Unlike most computer crime / misuse areas which are clear cut in terms of actions and legalities (e. g. software piracy), computer hacking is more difficult to define. Computer hacking always involves some degree of infringement on the privacy of others or damage to computer-based property such as files, web pages or software. The impact of computer hacking varies from simply being simply invasive and annoying to illegal. There is an aura of mystery that surrounds hacking, and a prestige that accompanies being part of a relatively elite group of individuals who possess technological savvy and are willing to take the risks required to become a true hacker. An interesting alternative view of how hackers positively impact areas such as software development and hacker ideology is presented in  Technology and Pleasure: Considering Hacking Constructive. WHO IS A HACKER In the computer security context, a  hacker  is someone who seeks and exploits weaknesses in a computer or computer network. Hackers may be motivated by a multitude of reasons, such as profit, protest, or challenge. The subculture that has evolved around hackers is often referred to as the computer underground but it is now an open  community. While other uses of the word hacker exist that are not related to computer security, such as referring to someone with an advanced understanding of computers and computer networks,  they are rarely used in mainstream context. They are subject to the long standing  hacker definition controversy  about the true meaning of the term  hacker. KINDS OF HACKERS White Hat A  white hat hacker  breaks security for non-malicious reasons, perhaps to test their own security system or while working for a security company which makes security software. The term white hat in Internet slang refers to an  ethical hacker. This classification also includes individuals who perform  penetration tests  and  vulnerability assessments  within a contractual agreement. The EC-Council, also known as the International Council of Electronic Commerce Consultants, is one of those organizations that have developed certifications, courseware, classes, and online training overing the diverse arena of Ethical Hacking. Black Hat A black hat hacker is a hacker who violates computer security for little reason beyond maliciousness or for personal gain (Moore, 2005). Black hat hackers form the stereotypical, illegal hacking groups often portrayed in popular culture, and are the epitome of all that the public fears in a computer criminal†   Black hat hackers brea k into secure networks to destroy data or make the network unusable for those who are authorized to use the network. They choose their targets using a two-pronged process known as the pre-hacking stage. Part 1: Targeting The hacker determines what network to break into during this phase. The target may be of particular interest to the hacker, either politically or personally, or it may be picked at random. Next, they will  port  scan a network to determine if it is vulnerable to attacks, which is just testing all ports on a host machine for a response. Open ports—those that do respond—will allow a hacker to access the system. Part 2: Research and Information Gathering It is in this stage that the hacker will visit or contact the target in some way in hopes of finding out vital information that will help them access the system. The main way that hackers get desired results from this stage is from social engineering, which will be explained below. Aside from social engineering, hackers can also use a technique called dumpster diving. Dumpster diving is when a hacker will literally search through users garbage in hopes of finding documents that have been thrown away, which may contain information a hacker can use directly or indirectly, to help them gain access to a network. Part 3: Finishing The Attack This is the stage when the hacker will invade the preliminary target that he/she was planning to attack or steal. Many hackers will be caught after this point, lured in or grabbed by any data also known as a  honeypot  (a trap set up by computer security personnel). Grey Hat A grey hat hacker is a combination of a Black Hat and a White Hat Hacker. A Grey Hat Hacker may surf the internet and hack into a computer system for the sole purpose of notifying the administrator that their system has been hacked, for example. Then they may offer to repair their system for a small fee. Hacktivists Some hacker activists are motivated by politics or religion, while others may wish to expose wrongdoing, or exact revenge, or simply harass their target for their own entertainment. State Sponsored Hackers Governments around the globe realize that it serves their military objectives to be well positioned online. The saying used to be, â€Å"He who controls the seas controls the world,† and then it was, â€Å"He who controls the air controls the world. † Now it’s all about controlling cyberspace. State sponsored hackers have limitless time and funding to target civilians, corporations, and governments. Spy Hackers Corporations hire hackers to infiltrate the competition and steal trade secrets. They may hack in from the outside or gain employment in order to act as a mole. Spy hackers may use similar tactics as hacktivists, but their only agenda is to serve their client’s goals and get paid. Cyber Terrorists These hackers, generally motivated by religious or political beliefs, attempt to create fear and chaos by disrupting critical infrastructures. Cyber terrorists are by far the most dangerous, with a wide range of skills and goals. Cyber Terrorists ultimate motivation is to spread fear, terror and commit murder. VARIOUS ATTACKS USED BY A HACKER PHISHING Phishing  is a way of attempting to acquire information such as usernames,passwords, and credit card details by masquerading as a trustworthy entity in anelectronic communication. Communications purporting to be from popular social web sites, auction sites, online payment processors or IT administrators are commonly used to lure the unsuspecting public. Phishing is typically carried out by  e-mailspoofing  or  instant messaging,  and it often directs users to enter details at a fake website whose  look and feel  are almost identical to the legitimate one. Phishing is an example of  social engineering  techniques used to deceive users,  and exploits the poor usability of current web security technologies. Attempts to deal with the growing number of reported phishing incidents include  legislation, user training, public awareness, and technical security measures. A phishing technique was described in detail in 1987, and the first recorded use of the term phishing was made in 1996. The term is a variant of  fishing,  probably influenced by  phreaking,  and alludes to baits used in hopes that the potential victim will bite by clicking a malicious link or opening a malicious attachment, in which case their financial information and passwords may then be stolen. KEY LOGGING These are  software  programs designed to work on the target computer’s  operating system. From a technical perspective there are five categories: * Hypervisor-based: The keylogger can theoretically reside in a  malware  hypervisor  running underneath the operating system, which remains untouched. It effectively becomes a  virtual machine. Blue Pill  is a conceptual example. * Kernel-based: This method is difficult both to write and to combat. Such keyloggers reside at the  kernel level  and are thus difficult to detect, especially for user-mode applications. They are frequently implemented as  rootkits  that subvert the operating system kernel and gain unauthorized access to the hardware, making them very powerful. A keylogger using this method can act as a keyboard  device driver  for example, and thus gain access to any information typed on the keyboard as it goes to the operating system. API-based: These keyloggers  hook  keyboard  APIs; the operating system then notifies the keylogger each time a key is pressed and the keylogger simply records it. Windows APIs on such as  GetAsyncKeyState(),  GetForegroundWindow(), etc. are used to poll the state of the keyboard or to subscribe to keyboard events. [1]  These types of keyloggers are the easiest to write, but where constant polling of each key is required, they can cause a noticeable increase in  CPU  usage, and can also miss the occasional key. A more recent example simply polls the  BIOS  for pre-boot authentication  PINs  that have not been cleared from memory. * Form grabbing based:  Form grabbing-based keyloggers log  web form  submissions by recording the web browsing onsubmit event functions. This records form data before it is passed over the Internet and bypasses  HTTPS  encryption. * Packet analyzers: This involves capturing network traffic associated with  HTTP POST  events to retrieve unencrypted passwords. Remote access  software  keyloggers These are local software keyloggers with an added feature that allows access to the locally recorded data from a remote location. Remote communication may be achieved using one of these methods: * Data is uploaded to a website, database or an  FTP  server. * Data is periodically emailed to a pre-defined  email address. * Data is  wirelessly  transmitted by means of an attached hardware system. * The software enables a remote login to the local machine from the Internet or the local network, for data logs stored on the target machine to be accessed. Related features Software Keyloggers may be augmented with features that capture user information without relying on keyboard key presses as the sole input. Some of these features include: * Clipboard logging. Anything that has been copied to the  clipboard  can be captured by the program. * Screen logging. Screenshots  are taken in order to capture graphics-based information. Applications with screen logging abilities may take screenshots of the whole screen, just one application or even just around the mouse cursor. They may take these screenshots periodically or in response to user behaviours (for example, when a user has clicked the mouse). A practical application used by some keyloggers with this screen logging ability is to take small screenshots around where a mouse has just clicked; these defeat web-based keyboards (for example, the web-based screen keyboards that are often used by banks) and any web-based on-screen keyboard without screenshot protection. * Programmatically capturing the text in a  control. The  Microsoft Windows  API  allows programs to request the text value in some controls. This means that some passwords may be captured, even if they are hidden behind password masks (usually asterisks). * The recording of every program/folder/window opened including a screenshot of each and every website visited, also including a screenshot of each. REMOTE ADMINSTRATIVE TOOL(RAT) A  remote administration tool  (a  RAT) is a piece of software that allows a remote operator to control a system as if he has physical access to that system. While  desktop sharing  and  remote administration  have many legal uses, RAT software is usually associated with criminal or malicious activity. Malicious RAT software is typically installed without the victims knowledge, often as payload of a  Trojan horse, and will try to hide its operation from the victim and from  security software. The operator controls the RAT through a network connection. Such tools provide an operator the following capabilities: * Screen/camera capture or image control * File management (download/upload/execute/etc. ) * Shell control (from command prompt) * Computer control (power off/on/log off if remote feature is supported) * Registry management (query/add/delete/modify) Other software product-specific functions Its primary function is for one computer operator to gain access to remote PCs. One computer will run the client software application, while the other computer(s) operate as the host(s). CLICK-JACKING Clickjacking is possible because seemingly harmless features of HTML web pages can be employed to perform unexpected actions. A clickjacked page tricks a user into performing undesired act ions by clicking on a concealed link. On a clickjacked page, the attackers load another page over it in a transparent layer. The users think that they are clicking visible buttons, while they are actually performing actions on the hidden page. The hidden page may be an authentic page, therefore the attackers can trick users into performing actions which the users never intended. There is no way of tracing such actions to the attackers later, as the users would have been genuinely authenticated on the hidden page. Clickjacking is possible because seemingly harmless features of HTML web pages can be employed to perform unexpected actions. A clickjacked page tricks a user into performing undesired actions by clicking on a concealed link. On a clickjacked page, the attackers load another page over it in a transparent layer. The users think that they are clicking visible buttons, while they are actually performing actions on the hidden page. The hidden page may be an authentic page, therefore the attackers can trick users into performing actions which the users never intended. There is no way of tracing such actions to the attackers later, as the users would have been genuinely authenticated on the hidden page. Examples A user might receive an email with a link to a video about a news item, but another valid page, say a product page on amazon. com, can be hidden on top or underneath the PLAY button of the news video. The user tries to play the video but actually buys the product from Amazon. Other known exploits include: * tricking users into enabling their webcam and microphone through Flash (which has since been corrected by Adobe); * tricking users into making their social networking profile information public; * making users follow someone on Twitter; share links on Facebook SPAMS Email spam, also known as  junk email  or  unsolicited bulk email  (UBE), is a subset of  electronic spam  involving nearly identical messages sent to numerous recipients by  email. Definitions of spam usually include the aspects that email is unsolicited and sent in bulk. One subset of UBE is  UCE  (unsolicited commercial email). The opposite of spam, email which one wants, is called ham, us ually when referring to a messages automated analysis (such as Bayesian filtering). Email spam has steadily grown since the early 1990s. Botnets, networks of  virus-infected computers, are used to send about 80% of spam. Since the expense of the spam is borne mostly by the recipient,  it is effectively  postage due  advertising. The legal status of spam varies from one jurisdiction to another. In the United States, spam was declared to be legal by the  CAN-SPAM Act of 2003  provided the message adheres to certain specifications. ISPs  have attempted to recover the cost of spam through lawsuits against spammers, although they have been mostly unsuccessful in collecting damages despite winning in court. Spammers collect email addresses from chatrooms, websites, customer lists, newsgroups, and viruses which harvest users address books, and are sold to other spammers. They also use a practice known as email appending or epending in which they use known information about their target (such as a postal address) to search for the targets email address. According to the Message Anti-Abuse Working Group, the amount of spam email was between 88–92% of email messages sent in the first half of 2010. PREVENTIVE MEASURES TO OVERCOME THE ATTACKS OF HACKERS KEYLOGGERS SCAN THE FILE WITH â€Å"DR. WEB LINK CHECKER†BEFORE DOWNLOADING. SCAN THE FILE WITH ONLINE MULTIPLE ANTI-VIRUS ENGINE IE. , www . novirusthanks org USE ANTI KEYLOGGERS LIKE ZEMANA,KEYSCRAMBERS ETC.. RATS STRICTLY FOLLOW THE INSTRUCTIONS OF THE ANTI-VIRUS.. ALWAYS USE AN UPDATED ANTI-VIRUS. DONT DOWNLOAD ANY FILE FROM AN ANONYMOUS WEBSITE. PHISHING ALWAYS TYPE THE COMPLETE URL OF THE INTENDED WEBPAGE FOR LOGIN. USE ANTI-VIRUS WHICH HAS WEB BROWSER INTERGRATION FACILITY TO COMBAT PHISHING LIKE KASPERSKY ETC.. NEVER LOGIN IN ANY LINK WITHOUT VERIFING ITS AUTHENTICATION. SPAM Some Facebook users were fooled into ‘verifying’ their account. Many Facebook walls were flooded with ‘verify  your/my account’ spam messages/wall posts. My advice to all Facebook users. To get rid of FB spams, do not click  the link. As simple as that. Clicking the link will just cause you to become one of the spam victims. It will automatically post the same spam messages on different Facebook walls. CONCLUSION * Data Security is the means of ensuring that data is kept safe from corruption and that access to it is suitably controlled. * . The Internet is a scary place. Criminals have the ability to hide behind their computers, or even other people’s computers ,they attempt to break into computer to steal personal information or to use it for their own purposes. * So to protect your Data with a firewall so that you are not an easy target to hackers and viruses in the future * When you leave your house, you lock your doors to prevent robbery, why not use a firewall to put a lock on your computer. AUTHORS: G. VAMSHI KRISHNA A. K. A h4x0r le610n, Computer Science amp; Engineering, 4nd year B. Tech, WARANGAL INSTITUTE OF TECHNOLOGY amp; SCIENCE.

French education system essays

French education system essays D'abord, les tudes, en France, sont srieux ! Aux Etats-Unis on peut terminer le lyce sans passer un examen (mais à §a va changer tout de suite avec les nouvelle loi de Grey Davis notre `gouverner d'Etat de Califorie). En France les lycens doivent passer le bac, c'est dire, le baccalaurate. C'est un examen trs important qui marque la fin des tudes secondaires et qui determine, en grande partie, l'avenir des lycens. S'ils sont reà §us, ils peuvent aller l'universit et continuer leurs tudes. S'ils ratent le bac, ils peuvent redoubler et se reprsenter l'anne suivante, ou bien ils peuvent faire des tudes techniques, ou entrer dans la vie professionelle, ou, pour les garà §ons, faire leur service militaire. Il y a plusiers types de bac. Ils sont dsigns par des lettres. Dans chaque srie, l'lve doit choisir une spcialit. Il y trois sries principales avec leurs spcialits. Il y le Srie littraire, le Bac L avec langues vivantes, lettres classiques, art et mathmatiques. Le Srie conomique et sociale, Bac ES avec les spcialits de sciences conomiques et sociale, mathmatiques, et langues vivantes. Et finalment, il y a le Srie scientifique, le bac S avec mathmatiques, physique chimie, sciences de la vie et de la terre, et technologie industrielle. Ces spcialits sont important parce qu'elles dterminent le genre d'tudes universitaires qu'on peut faire, et, par consquent, sa profession future. Par exemple, si on veut à ªtre mdecin ou pharmacien, il est conseill de faire un bac S. spcialit sciences de la vie et de la terre. Si on pense faire des tudes de droit, et devenir avocat, il est pr ...

The Confession and Crime Assignment Example | Topics and Well Written Essays - 500 words

The Confession and Crime - Assignment Example Han and his wife lived peacefully as described by the Chinese stagehand. Similarly, Kuzmich lived well with people even though they took advantage of him. He is a humble man who thinks everyone around him lives a good life until they start borrowing from him. Second Topic Sentence: Both Han and Kuzmich did not get along in their respective marriages. It seems that there was nothing so intimate between the two main characters and their wives. Threats of divorce were all over. Specific Support: Han feels that the child is not his and that he married his wife when she was already pregnant. On the other hand, Kuzmich is thought of being a thief simply because his friends and his wife think that he steals from his workplace. Specific Support: Han cannot take decisive action towards his wife and the overwhelming hatred towards her is the possible cause of her murder. Kuzmich too cannot openly tell his friends that he does not have the amount of money they think he has. He goes ahead to steal just to please his greedy friends. Specific Support: Han selfishly thinks that his wife is unfaithful and that he can live without him. Kuzmich also looks forward to living a good life just like his friends despite earning a little income. Conclusion with a Clincher: Han and Kuzmich have had a tragic ending because of the people around them and the circumstances around them. Han’s crime was provoked by his own feeling and attitude towards his wife. Also, Kuzmich’s friends seem to have influenced him in stealing the money from the cash box.  

Hometown Deli Competitive Analysis Case Study Example | Topics and Well Written Essays - 1250 words

Hometown Deli Competitive Analysis - Case Study Example However, with the threat of looming competition, it is important to analyze the market and determine the possible change in profitability. It is also important to identify a strategy that will be used to improve the business and make it viable in this time. The first aspect of Porter’s five force analysis is the supplier power, which is the importance of the supplier when serving more than one competitor (Porter, 2008). From the analysis of Hometown Deli, it can be determined that the previous owner built a network of suppliers. This means that the supplier is a powerful force in the industry. From the products of the deli, it is evident that there are many possible avenues for getting new suppliers, so the threat of supplier power is low. The best strategy to deal with the existing suppliers is to consolidate their services to guard from competition. This can be done by using one supplier and ensuring that long-term contracts are used with the supplier. The second aspect of P orter’s model is buyer power, and is probably the most important part of the analysis (Porter, 2008). From the history of the deli, it is evident that the previous owner built a network of customers, and the new owner has to find a strategy of retaining these customers. The information indicates that the deli has been a local hotspot for many years, and the best strategy to deal with the power of the buyer is to ensure that these customers do not move with the potential competition. This is done by ensuring that the customers retain their image of the company. In this case, Hometown Deli should provide promotional content aimed at retaining old customers, like using loyalty programs for old customers and introducing prices for returning customers. The other factor is the threat of new entrants, which is determined by the existing competition in the region, cost advantages, barriers to entry and access to distribution (Porter, 2008). In the case of Hometown Deli, there is a bi g threat from competition, mainly because there are low barrier to entry and the potential competition has bigger profits, which means that they have more access to promotional content. This means that the deli is faced with the biggest threat from competition, ad to deal with it, management should come up with a way of increasing their competitive presence. The best strategy for this is to find extra sources of finance and improve the technological presence in the region. If the deli improves the service offered to its customers, it would make it easier to retain customers to the deli. The deli should be brought up to date in terms of competitive presence in the region. The fourth factor is the threat of substitutes, which is the competition faced by a business from the possibility of clients using substitute products (Porter, 2008). In the case of Hometown Deli, the main substitute product is fast food restaurant products, which is not so much of a problem. This force can be addre ssed by consolidating the clients’ preference for the deli product. The last factor is the degree of rivalry, which refers to the competition that would be posed by a rival company. Increased competition can drive profits very low since the market is very concentrated. With the threat of only one rival, it is important to establish a strong identity; otherwise the market could become a monopoly, especially since the potential com

The Influence of Social Thinking Essay Example | Topics and Well Written Essays - 750 words

The Influence of Social Thinking - Essay Example Many people judge another person's personality and mood by only processing a small amount of information about them. We may see a person laughing at the grocery store and think they have a jovial spirit. When we see them at work, they may be cold and aloof. People are often judged by these situational moods. Yet, the person is adapting to the situation. This overemphasis on personality and the underestimation of the situation is known as fundamental attribution error (Myers 706). The person has changed their behavior to react to a different situation. This error can cause us to label and catalog people falsely. When we use only mood and behavior to judge a person and overlook the situation it's an attribution error. When we react to situations it is sometimes difficult to understand how much is our behavior being controlled by our own attitudes and how much our behavior is controlling what we think. Often times people are told 'make the best of it'. There may be a class that a student doesn't enjoy yet approaches it with a positive attitude. If other outside influences are minimal, we may do well in the class (Myers 709). However, if people tell us we will fail in the class, and we don't take any action to change the attitude, we will likely fail. Knowing that our attitude can change our behavior can be beneficial in changing our lives. We may not be able to change dramatically or quickly, but we may be able to alter our behavior a step at a time. The foot-in-the-door phenomenon states that when people agree to a small action they are more likely to agree to a larger action at a later time (Myers 709). By understanding this we can also incorporate the cognitive dissonance theory that states that we can bring our "attitudes in line with our actions" (Myers 711). By taking an attitude that we want to project, we can alter our behavior. As much as our own attitudes and social situations determine our behavior, the group that we are in exerts even more pressure. Experiments by Solomon Asch confirmed that people feel a need to conform (Myers 714). The group we are in exaggerates this need. If we are insecure, the group is large, we admire the group, and the group is unanimous, it increases our likelihood of conforming (Myers 715). This is how lone holdouts on juries are eventually swayed into changing their vote. It is also how we are persuaded to take an action we may feel is wrong. We may also conform to a group for the same reasons and elicit a positive outcome. A study group, church meeting, or volunteer organization may prompt us to behave in a positive manner. Yet, in some groups there is no general consensus and opposing views are suppressed resulting in "groupthink" (Myers 722). Panels, boards, and committees have often made serious blunders by succumbing to the phenomenon. While these group pressures may result in a bad decision, they can also become destructive and overpowering. The experiments of Stanley Milgram illustrated how far people were willing to go to conform (Myers 717). People will go beyond simply conforming and to the level of blind obedience. This is especially true if the group influence has the perception of authority and the authority is close at hand (Myers 717). The influence of people is also seen when they affect our actions such as in "social facilitation" (Myers

Non Equillibrium Green’s Function Technique

Non Equillibrium Green’s Function Technique NON EQUILLIBRIUM GREEN’S FUNCTION TECHNIQUE USED FOR THE METAL-INSULATOR-METAL DIODES ANSHUMAN Electronics and Communication Dept. NIT Kurukshetra Abstract – In this paper theoretical analysis of NEGF method, including the transport equation and Poisson equation, is done followed by the derivation of an analytical model using NEGF tunnelling probability through any number of insulating layers. Numerical NEGF simulator are shown matching with the AF-TMM simulator results. INTRODUCTION THE STUDY OF tunnelling phenomena in Metal Insulator Metal (MIM) is an important topic for the aim of the development of rectennas for energy harvesting and infrared detectors applications. Although the interest in Metal-Insulator-Metal (MIM) diodes dates back to 1950s [1]–[4], but they attracted the attention again in the last few years due to its applications, energy harvesting [5]–[8] and infrared/terahertz detectors [9]–[11]. Earlier, various analytical expressions for the tunnelling transmission probability through MIM diodes were developed based on WKB approximation [2]–[4]. However, the WKB does not take into consideration the wave function reflections at the interface between different layers [14]. Therefore, there came the need for other models to simulate the tunnelling probability. Non Equilibrium Green Function (NEGF) [12] numerical method is one of the methods used to calculate the tunnelling transmission probability [15]–[18]. It is an accurate numerical method, but it needs long time of calculations on a PC in comparison to other analytical models. Any program used for the simulation of a device performs a solution of transport equation and â€Å"Poisson† equation [19].The transport equation gives the electron density, n(r) and the current, I for a known potential profile U(r), while Poisson equation gives the effective U(r), felt by an electron due to the presence of other electron in its vicinity. Here, in this paper the Quantum transport, Green’s functions and its various equations under non equilibrium condition are discussed and a detailed quantum mechanical modeling of the tunnelling current through MIM diodes is presented. An analytical expression for the tunnelling transmission probability is presented using the NEGF equations for any number of insulator layers between the two metals. Fig.1. Transport of electrons for single energy level device The paper is organized as follows: in Section II, the transport equations are discussed. In section III NEGF equations for MIM Diode is described in detail. The governing equations and numerical implementation of it is outlined. The material parameters used in the simulation are also summarized. GENERAL TRANSPORT EQUATION Let’s consider the model for a single device sandwiched between two metals 1and 2ION THE METAL-INSULATOR.ce of other electron in its vicinity.port and 111111111111111111111111111111111111111111, as shown in fig. 1.The device is assumed to be having a single energy level, Ô . Our first aim is to find the number of electrons, N in the device. Let Ef be the Fermi level set by the work function of the two metal contacts under the equilibrium condition. On applying the bias voltage, Vb between metal 1 and 2, the Fermi- energies of two metals gets modified to  µ1 and  µ2 respectively and given as [19]: (1) This difference in Fermi-energy gives rise to a non-equilibrium condition and hence two different Fermi-functions for the two contacts. If device is in equilibrium with metal 1, then number of electrons will be f ­1 but if it is in equilibrium with metal 2, number of electrons will be f ­2, where (2) Let and be the rate of escape of electron from device into metal 1 and metal 2 respectively. Therefore the currents I1 and I2 crossing metal1 and 2 interfaces are given as[20]: And (3) For I1 = I2 = I, we get steady-state number of electrons N and current I as: (4a) (4b) Due to the applied bias voltage one of the reservoir keeps pumping the electron trying to increase the number while the other keeps emptying it trying to lower the number. Ultimately, there is a continuous flow of current, I (eq. 4b) in the external circuit. Assuming à °Ã‚ Ã…“†¡1 > à °Ã‚ Ã…“â‚ ¬ > ÃŽ ¼2 and the temperature is low enough that f1 (ÃŽ µ) ≠¡ f0 (ÃŽ µ − ÃŽ ¼1) ≈ 1 and f2 (ÃŽ µ) ≠¡ f0 (ÃŽ µ − ÃŽ ¼2) ≈ 0, the Eq. 4b simplifies to [21]: If = (5) Eq.5 suggests that we can flow an unlimited current through this one level device if we increase, i.e. by coupling the device more and strongly to the metal contacts. But the maximum conductance of a one-level device is equal to [20], so there must be some reduction factor. This reduction is due to the broadening of the discrete level that occurs because of increased coupling of the device with the two metals. This broadened discrete level can be described by the distribution: With line-width of ÃŽ ³ and shift of level from ÃŽ µ to ÃŽ µ+à ¢Ã‹â€ Ã¢â‚¬  , where. This broadening phenomena modifies the Eqs. (4a, b) to include an integral over all energies weighted by the distribution D(E) [13]: (6a) (6b) Using algebraic manipulation Eqs. (6a, b) becomes: (7a) (7b) Where (8) (9) Till now we have discussed device with single energy level ÃŽ µ. But in practical situation (i.e. for real devices) there exist multiple energy levels. Any device, in general, can be represented by a Hamiltonian matrix, whose eigenvalues tells about the allowed energy levels. For example if we describe the device using an effective mass Hamiltonian H = then it can be represented with a (NxN) matrix by choosing a discrete lattice with N point and applying methods of finite-differences [13]. This corresponds to using a discretized real space basis. Similarly, we define self-energy matrices [∑ ­1,2] which describe the broadening and shift of energy levels due to coupling with the two metals. The required NEGF equations now can be obtained from Eqs(7a, b) by replacing scalar quantities ÃŽ µ and ÏÆ' ­1,2 with the corresponding matrices [H] and [∑ ­1,2], and is given as: , (10) , (11) The number of electrons N, in the device is replaced with the density matrix, given by: {} (12) Current is still represented by Eq. (7b). The transmission can be given as the trace of the analogous matrix quantity: (13) TRANSMISSION EQUATION FOR MIM DIODE USING NEGF EQUATIONS The 1D time-independent single-particle Schrà ¶dinger equation is given by [13]: Where, is the reduced Plank constant, ψ(x) is the electron wave-function, m is the effective mass and U(x) is the potential energy. If it is assumed that the insulator layers are divided into M grid points having uniform spacing, a, then finite difference discretization on the 1D grid is applied to Schrà ¶dinger equation Eq. (1) at each node i as follows [14]: (2) Where, represents the interaction between the nearest neighbour grid points i and i+1, Ui ≠¡ U (xi), and mi is the electron effective mass between the nodes i and i + 1. The coupling of the potential barrier to the left and right metal electrodes is taken into consideration by rewriting Eq. (1) for i =1 and i = M with open boundary conditions expressed at Metal1/Insulator and Insulator/Metal2 interfaces. So, Schrà ¶dinger equation now takes the following form [13]: (3) Where, H is the M Ãâ€" M Hamiltonian matrix of the insulator potential, I is the M Ãâ€" M identity matrix, ψ is the wavefunction M Ãâ€" 1 vector and S is M Ãâ€" 1 vector. ∑L and ∑R are the M Ãâ€" M self-energies of the left and right contacts respectively. Fig. 1. Potential of a stack of N insulator materials under applied bias voltage, Vb. Each insulator layer is characterized by a barrier height (Uj), a thickness (d j), a dielectric constant ÃŽ µ j, and an effective mass (m j). Now, under a tri-diagonal form H can be rewritten as: ∑L and ∑R are given as: The solution of Eq. (1) can be given in the terms of retarded Green’s function as where is MÃâ€"M retarded Green’s function [13]: The rate of escape of electron to either left or right metal from a given state can be taken into consideration by defining two quantities, ΓL and ΓR [14]. Hence, the tunnelling probability can now be computed as [14]: COMPARISION OF NEGF MODEL WITH OTHER MODELS A model of MIIM diode was simulated using NEGF, AF-TMM and WKB Approximation for a comparative analysis of their transmission probability vs. electron transmission energy curve. The parameter spacing, a, for the NEGF calculation was assumed equal to the hundredth of the insulator layer thickness. This was found adequate for reasonable simulation time. The effective mass was assumed equal to the free mass of the electron throughout the MIM structure. Fig.3 below shows theof the simulated MIIM of Nb/Nb2O5 (2nm)-Ta2O5 (1nm)/Nb at 0.1V of bias voltage. A complete matching between AF-TMM and NEGF results is observed. Fig.3. Transmission probability T (Ex) versus the electron transmission energy calculated using AF-TMM, NEGF, and WKB at Vb = 0.1 V for Nb/Nb2O5/Ta2O5/ Nb MIIM diode. Fig.4. Energy band diagram of the MIIM diode used for simulation REFERENCES J. G. Simmons, â€Å"Electric tunnel effect between dissimilar electrodes separated by a thin insulating film,† J. Appl. Phys., vol. 34, no. 9, pp. 2581–2590, Mar. 1963. J. G. Simmons, â€Å"Generalized formula for the electric tunnel effect between similar electrodes separated by a thin insulating film,† J. Appl. Phys., vol. 34, no. 6, pp. 1793–1803, 1963. R. Stratton, â€Å"Volt-current characteristics for tunneling through insulating films,† J. Phys. Chem. Solids, vol. 23, no. 9, pp. 1177–1190, Sep. 1962. J. G. 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Do the Right Thing Scene Analysis Essay -- Film Analysis

Do the Right Thing is a dramatic comedic film that was directed by Spike Lee. The movie was released in 1989. Lee served in three capacities for the film: writer, director and producer of the movie, Ernest Dickenson was the cinematographer and Barry Alexander Brown was the film’s editor. For this film, Lee garnered together some notable actors and actresses, including Ruby Dee and Ossie Davis, Rosie Perez, Samuel L. Jackson, John Tuturro and Martin Lawrence. The setting of the movie is in Bedford-Stuyvesant; which is a neighborhood in Brooklyn, New York. This particular neighborhood is made up of several ethnic groups that include African Americas, Italians, Koreans, and Puerto Ricans. The movie takes place on a particularly hot day during the summer time. The extreme heat causes tensions between the different races in the neighborhood. In this paper, I will attempt to show how mise-en-scà ¨ne, camera work, editing, and sound are used to convey â€Å"explicit† an d â€Å"implicit† meaning in one scene in Do the Right Thing. The scene that I will be analyzing takes place towards the end of the movie in which all the racial tensions that were boiling over erupted like a volcano and spewed out. This particular scene is about five minutes in length and is composed of about 25 shots. It takes place at the end of the day after Sal’s Famous Pizzeria has closed. We see that the pizzeria is closed and Sal is having a conversation with his sons Vito and Pino about him wanting to change the name of his store to Sal and Son’s Pizzeria. He also tells Mookie, â€Å"You are like a son to me.† The suddenly we here banging on the door, it’s the neighborhood kids wanting to get a slice of pizza. Although the pizzeria is closed, Sal tells a reluctant Mookie... ...xt shot we observe them on the outside, for this Brown uses a straight cut rather than a jump cut to promote continuity into the next scene. All the scenes in the movie including this one take places in chronological order in a linear fashion. The editor also uses reverse angle cutting as well. In the end, this particular scene of Do Right Thing, has both implicit and explicit meanings. Work Cited Do the Right Thing. Dir. Spike Lee. Perf. Danny Aiello, John Turturro, Giancarlo Esposito, Martin Lawrence, Bill Nunn, Richard Edson, Roger Guenveur Smith and Spike Lee. Forty Acres and a Mule Filmworks.1989. Streaming (Netflix) â€Å"Do the Right Thing.† IMBD.com. Internet Movie Database, n.d. Web. 23 Apr. 2011. Stanley, Robert H. The Movie Idiom: Film as a Popular Art Form. Illinois: Waveland Press, Inc. 2011. Print