Some processors use VLIW techniques so each instruction drives multiple arithmetic units in parallel.

   Special loop controls, such as architectural support for executing a few instruction words in a very tight loop without overhead for instruction fetches or exit testing

   Deliberate exclusion of a memory management unit. DSPs frequently use multi-tasking operating systems, but have no support for virtual memory or memory protection. Operating systems that use virtual memory require more time for context switching among processes, which increases latency.

   History

   Prior to the advent of stand-alone DSP chips discussed below, most DSP applications were implemented using bit-slice processors. The AMD 2901 bit-slice chip with its family of components was a very popular choice. These bit slice architectures would sometimes include a peripheral multiplier chip.

   In 1978, Intel released the 2920 as an "analog signal processor". It was designed as a microprocessor peripheral, and it had to be initialized by the host. The S2811 was likewise not successful in the market.

   In 1980 the first stand-alone, complete DSPs  were presented at the International Solid-State Circuits Conference '80.

   The first DSP produced by Texas Instruments (TI), the TMS32010 presented in 1983, proved to be an even bigger success. It was based on the Harvard architecture, and so had separate instruction and data memory. It already had a special instruction set, with instructions like load-and-accumulate or multiply-and-accumulate.

   About five years later, the second generation of DSPs began to spread. Some of them operated on 24-bit variables and a typical model only required about 21ns for a MAC (multiply-accumulate).

   The main improvement in the third generation was the appearance of application-specific units and instructions in the data path, or sometimes as coprocessors. These units allowed direct hardware acceleration of very specific but complex mathematical problems, like the Fourier-transform or matrix operations.

   The fourth generation is best characterized by the changes in the instruction set and the instruction encoding/decoding.

   Modern DSPs

   Modern signal processors yield greater performance; this is due in part to both technological and architectural advancements like lower design rules, fast-access two-level cache, (E)DMA circuitry and a wider bus system.

   Texas Instruments produce the C6000 series DSP’s, which have clock speeds of 1.2 GHz and implement separate instruction and data caches.

   NXP Semiconductors produce DSP's based on TriMedia VLIW technology, optimized for audio and video processing. In some products the DSP core is hidden as a fixed-function block into a SoC, but NXP also provides a range of flexible single core media processors.

   Most DSP's use fixed-point arithmetic, because in real world signal processing the additional range provided by floating point is not needed, and there is a large speed benefit and cost benefit due to reduced hardware complexity. Floating point DSP's may be invaluable in applications where a wide dynamic range is required. Product developers might also use floating point DSP's to reduce the cost and complexity of software development in exchange for more expensive hardware, since it is generally easier to implement algorithms in floating point.

   Diverse Hacker Attack Methods

   The stereotyped image conjured up by most people when they hear the term "hacker" is that of a pallid, atrophied recluse cloistered in a dank bedroom, whose spotted complexion is revealed only by the unearthly glare of a Linux box used for port scanning with Perl. However, although computer skill is central to a hacker's profession, there are many additional facets that he must master. A real hacker must also rely on physical and interpersonal skills such as social engineering and other "wet work" that involves human interaction.

   Social Engineering

   Social engineering is not unique to hacking. In fact, many people use this type of trickery every day, both criminally and professionally. Whether it be haggling for a lower price on a lawn mower at a garage sale, or convincing your spouse you really need that new toy or outfit, you are manipulating the "target." Although your motives might be benign, you are guilty of socially engineering the other party.

   The Virtual Probe

   One example of social engineering that information technology managers face on a weekly basis is solicitation from vendors. An inimical form of sales takes the form of thinly disguised telemarketing. Straying far from ethical standards of sales technique, such vendors will attempt to trick you into giving them information so they can put your company's name on a mailing list.

   Here is one such attempt that we get regularly:

   "Hi, this is the copier repair company. We need to get the model of your copier for our service records. Can you get that for us?"

   Like the scam artist, a hacker often uses similar techniques. A popular method that hackers use is pretending to be a survey company. A hacker can call and ask all kinds of questions about the network operating systems, intrusion detection systems (IDSs), firewalls, and more in the guise of a researcher. If the hacker was really malicious, she could even offer a cash reward for the time it took for the network administrator to answer the questions. Unfortunately, most people fall for the bait and reveal sensitive network information.  

   One of the most common goals of a hacker is to obtain a valid user account and password.

   For example, many organizations use a virtual private network (VPN) that enables remote employees to connect to the network from home and essentially become a part of the local network. As VPNs are set up and maintained by the IT department, hackers will often impersonate an actual employee and ask one of the IT staff for the password by pretending to have lost the settings. If the IT employee believes the person, he willingly and often gladly hands over the keys. Voila! The hacker now can connect from anywhere on the Internet and use an authorized account to work his way deeper into the network.

   Social Spying

   Social spying is the process of "using observation to acquire information." Although social engineering can provide a hacker with crucial information, small businesses are better protected against social engineering because many people in very small companies know each other.

   To illustrate one of the nontechnical ways social spying can be used, consider how many people handle ATM cards. For example, do you hide your PIN when you take money out at the ATM? Take note of how people protect their PIN the next time you are in line at the ATM. You will probably note most people do not care. Most will whip out their card and punch the numbers without a care for who could be watching. If the wrong person memorized the PIN, he would have all the information needed to access the funds in the account, provided he could first get his hands on the ATM card. Thus, a purse-snatcher would not only get the money just withdrawn from an ATM, but could easily go back and withdraw the entire day's limit.

   In addition to snooping on people as they actively type their user information, most offices have at least several people who are guilty of posting their password on or near their computer monitor. This type of blatant disregard for security is every network administrator's worst nightmare. Regardless of repeated memos, personal visits, and warnings, some people seem to always find an excuse to post their network password right in plain view.

   Sniffing

   A sniffer is a program and/or device that monitors all information passing through a computer network. It sniffs the data passing through the network off the wire and determines where the data is going, where it's coming from, and what it is. In addition to these basic functions, sniffers might have extra features that enable them to filter a certain type of data, capture passwords, and more. Some sniffers (for example, the FBI's controversial mass-monitoring tool Carnivore) can even rebuild files sent across a network, such as an email or Web page.

   A sniffer is one of the most important information gathering tools in a hacker's arsenal. The sniffer gives the hacker a complete picture (network topology, IP addresses) of the data sent and received by the computer or network it is monitoring. This data includes, but is not limited to, all email messages, passwords, user names, and documents. With this information, a hacker can form a complete picture of the data traveling on a network, as well as capture important tidbits of data that can help her gain complete control over a network.

   How Does a Sniffer Work?

   For a computer to have the capability to sniff a network, it must have a network card running in a special mode. This is called promiscuous mode, which means it can receive all the traffic sent across the network. A network card will normally only accept information that has been sent to its specific network address. This network address is properly known as the Media Access Control (MAC) address. You can find your own MAC address by going to the Windows Taskbar and clicking Start?Run and typing winipcfg (for Windows 95/98/ME) or ipconfig /all (for Windows NT/2000/.NET Server). The MAC address is also called the physical address.

   There are different layers involved in network communications. Normally, the Network layer is responsible for searching the packets of information for their destination address. This destination address is the MAC address of a computer. There is a unique MAC address for every network card in the world. Although you can change the address, the MAC address ensures that the data is delivered to the right computer. If a computer's address does not match the address in the packet, the data is normally ignored.

   The reason a network card has this option to run in promiscuous mode is for troubleshooting purposes. Normally, a computer does not want or need information to be sent to other computers on the network. However, in the event that something goes wrong with the network wiring or hardware, it is important for a network technician to look inside the data traveling on the network to see what is causing the problem. For example, one common indication of a bad network card is when computers start to have a difficult time transferring data. This could be the result of information overload on the network wires. The flood of data would jam the network and stop any productive communication. After a technician plugs in a computer with the capability to examine the network, he would quickly pinpoint the origin of the corrupt data, and thus the location of the broken network card. He could then simply replace the bad card and everything would be back to normal.

   Another way to visualize a sniffer is to consider two different personality types at a cocktail party. One type is the person who listens and replies to conversations in which he is actively involved. This is how a network card is supposed to work on your local machine. It is supposed to listen and reply to information sent directly to it. On the other hand, there are those people at the party who stand quietly and listen to everyone's conversation.

   How Hackers Use Sniffers

   As previously mentioned, sniffers like this are used every day to troubleshoot faulty equipment and monitor network traffic. Hackers can use this or similar tools to peer inside a network. However, they are not out to troubleshoot. Instead, they are out to glean passwords and other gems.

   How to Detect a Sniffer

   There are a few ways a network technician can detect a NIC running in promiscuous mode. One way is to physically check all the local computers for any sniffer devices or programs. There are also software detection programs that can scan networks for devices that are running sniffer programs (for example, AntiSniff). These scanner programs use different aspects of the Domain Name Service and TCP/IP components of a network system to detect any malicious programs or devices that are capturing packets (running in promiscuous mode). However, for the average home user, there is really no way to detect whether a computer out on the Internet is sniffing your information. This is why encryption is strongly recommended.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

References 

1. Википедия - свободная энциклопедия

http://en.wikipedia.org/wiki/United_Kingdom

2. THE NATIONAL FORUM OF MODERN TECNOLOGY       http://naviny.by/rubrics/english/2007/09/17/ic_news_259_277040

 

3. Optimizing Digital Signal and Image Processing on Intel® Architecture. White - Paper Peter Carlston. January 2009.

    

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