Экология. НОВ.2019_Сборник_контрольных_работ_для_заочников_ФЗО_1. Технологический университет
 Скачать 1.02 Mb.
|
Вариант 4 для направления подготовки 10.03.01 Информационная безопасностьПрочитайте и письменно переведите текст на русский язык. DENIAL OF SERVICE ATTACKS Denial of service (DoS) attacks result in downtime or inability of a user to access a system. DoS attacks impact the availability tenet of information systems security. A DoS attack is a coordinated attempt to deny service by occupying a computer to perform large amounts of unnecessary tasks. This excessive activity makes the system unavailable to perform legitimate operations. When a disk fills up, the system locks an account out, a computer crashes, or a CPU slows down, the result is denial of service—hence the name. DoS attacks generally originate from a single computer. Once you detect a DoS attack, you can stop it easily. Two common types of DoS attacks are as follows: • Logic attacks—Logic attacks use software flaws to crash or seriously hinder the performance of remote servers. You can prevent many of these attacks by installing the latest patches to keep your software up to date. • Flooding attacks—Flooding attacks overwhelm the victim computer’s CPU, memory, or network resources by sending large numbers of useless requests to the machine. One of the best defenses against DoS attacks is to use intrusion prevention system (IPS) software or devices to detect and stop the attack. Intrusion detection system (IDS) software and devices can also detect DoS attacks and alert you when such attacks are in progress. Without a defense against DoS attacks, they can quickly overwhelm servers, desktops, and network hardware, slowing computing in your organization to a grinding halt. In some cases, these attacks can cripple an entire infrastructure. Most DoS attacks target weaknesses in the overall system architecture rather than a software bug or security flaw. Attackers can launch DoS attacks using common Internet protocols such as TCP and Internet Control Message Protocol (ICMP). A DoS attack launched through one of these protocols can bring down one or more network servers or devices by flooding it with useless packets and providing false information about the status of network services. This is known as a packet flood. One popular technique for launching a packet flood is a SYN flood. SYN is a TCP control bit used to initialize TCP/IP communication with another device. Normally, to establish communication, the host receiving the SYN bit immediately responds (with both the SYN and ACK bits) and awaits a confirmation. In a SYN flood, the attacker sends a large number of packets requesting connections to the victim computer; however, the ACK bit is never received. The victim computer records each request and reserves a place for the connection in a local table in memory. The victim computer then sends a confirmation back to the attacker, but the attacker never acknowledges the confirmation. All these reserved bits of memory are small, but as they accrue, the amount eventually fills the victim’s connections table to capacity until it runs out of memory for other operations. In the meantime, no legitimate users can connect to the victim computer, because the SYN flood has filled the connection table. The victim computer will remain unavailable until the connection requests time out. Another popular technique is smurfing. The smurf attack uses a directed broadcast to create a flood of network traffic for the victim computer. Both internal attackers and external attackers can launch DoS attacks. However, most attacks come from anonymous outsiders. Network intrusion detection (IDS/IPS) is usually effective at detecting these attacks. Security personnel routinely take aggressive steps to ensure that attackers cannot use their systems for malicious purposes. In addition, some web content providers and network device manufacturers now include new rules designed to prevent DoS attacks in their default configuration tables. Preventing attackers from gaining access to your computers is a full-time effort, but it’s one that is worth the expense. (English for Computer Science Students: учеб. пособие / Сост. Т. В. Смирнова, М. В. Юдельсон; науч. ред. Н. А. Дударева) II. Задайте к каждому абзацу 3 специальных вопроса. III. Найдите абзац, в котором выражена основная идея текста. IV. Напишите краткий план текста на английском языке. Вариант 1 для направления подготовки 38.03.01 Экономика (Бух.учет)Прочитайте и письменно переведите текст на русский язык. AVERAGE-COST This method prices inventory on the basis of the average cost of all similar goods available during the period. It is mainly used because it is simple and relatively easy to use. FIFO. This method assumes that inventory is used in the order it is purchased or produced. Under this method, ending inventory is stated at approximately current costs, with the oldest costs charged against current sales. In periods of inflation, this can cause "paper profits" to be recognised and taxed. It also results in the highest reported earnings. The FIFO method is probably the most commonly used inventory method. LIFO. This method became popular in prior years due to significant inflation. The LIFO method assumes that the most recently purchased or produced goods are used first - the opposite assumption from FIFO. Although generally it is a more difficult method to use, a simplified LIFO method of accounting for inventories is available to small businesses A taxpayer can use the simplified LIFO method if average annual gross receipts for the three preceding tax years do not exceed $5 million. In periods of inflation, LIFO results in lower inventory valuations, higher cost of sales and lower taxable income. This method is most commonly used by companies facing rising production and material costs. The LIFO inventory method is adopted by filing Form 970 with the income tax return for the tax year in which the method is first used. Overhead Costs. A mechanism must be established to capture overhead costs and relate them to the inventory's direct material and labour costs. Manufacturers typically allocate the "pool" of indirect costs to inventory on the basis of a standard unit, such as labour dollars or hours. In the US, once a method has been established, it cannot be changed without IRS permission. As a result, many of the planning techniques for inventory overhead costs need to be addressed when the business is starting. (Плюхина З.А. Английский для бухгалтеров и аудиторов) II. Задайте к каждому абзацу 3 специальных вопроса. III. Найдите абзац, в котором выражена основная идея текста. IV. Напишите краткий план текста на английском языке. |