Animation is the rapid display of a sequence of images of 2-D or 3-D artwork or model positions in order to create an illusion of movement. It is an optical illusion of motion due to the phenomenon of persistence of vision, and can be created and demonstrated in a number of ways. The most common method of presenting animation is as a motion picture or video program, although several other forms of presenting animation also exist.
2D animation figures are created and/or edited on the computer using 2D bitmap graphics or created and edited using 2D vector graphics. This includes automated computerized versions of traditional animation techniques such as of tweening, morphing, onion skinning and interpolated rotoscoping.
3D animation are digitally modeled and manipulated by an animator. In order to manipulate a mesh, it is given a digital skeletal structure that can be used to control the mesh. This process is called rigging. Various other techniques can be applied, such as mathematical functions (ex. gravity, particle simulations), simulated fur or hair, effects such as fire and water and the use of Motion capture to name but a few, these techniques fall under the category of 3d dynamics. Many 3D animations are very believable and are commonly used as Visual effects for recent movies.
Saturday, April 17, 2010
computer hardware component
The term computer has brought a revolution in today’s world. All the tasks that were earlier performed with man power are now being performed more efficiently with the help of computers. Computer has provide a job opportunities to large number of youths and thus have led to an all round development of the society. Due to the coming of computers a new industry known as the computer industry has developed. Various new IT companies have come forward and are engaged in researching, developing and manufacturing of various types of products related to computers. A computer comprises of various components, hardware components being one of them. Computer hardware can be described as the physical features of the computers that include digital circuitry etc. In comparison to software (the parts used within the hardware) computer hardware is not changed or modified much.
output device
input device
computer science the complete reference
output device
input device
computer science the complete reference
Bluetooth theory
What is Bluetooth ?
Bluetooth is a high-speed, low-power microwave wireless link technology, designed to connect phones, laptops, PDAs and other portable equipment together with little or no work by the user.
Bluetooth is the name for a short-range radio frequency (RF) technology that operates at 2.4 GHz and is capable of transmitting voice and data. The effective range of Bluetooth devices is 32 feet (10 meters). Bluetooth transfers data at the rate of 1 Mbps, which is from three to eight times the average speed of parallel and serial ports, respectively. It is also known as the IEEE 802.15 standards. It was invented to get rid of wires. Bluetooth is more suited for connecting two point-to-point devices, whereas Wi-Fi is an IEEE standard intended for networking.
When the Cabir mobile worm started to attack mobile devices and used Bluetooth to spread, many people were caught by surprise. It first appeared as a proof-of-concept virus written by the A29 group, was provided to an anti-virus company, and then later appeared in the wild. The worm started spreading from infected mobile phones using the Bluetooth wireless capabilities to search for the next victim and infect it based. This infection was based on a vulnerability in the Bluetooth implementation of several Nokia and Sony Ericsson phones. The virus was not dangerous, however, as it only drained the phone's battery and it still required the user to accept installation of the file. However, it showed that it is possible to write mobiles viruses that spread via Bluetooth, which may encourage a number of virus writers to take the same approach. Future Bluetooth viruses may very well be much more damaging. A good example of the potential damage that can be caused first appeared in Japan in 2001, where the virus blocked the ability to call emergency numbers. Recent vulnerabilities in Java, discovered by famous Polish security researcher Adam Gowdiak, could also be used by mobile virus writers to break the Java mobile security model and get access to the phone's memory, affecting many things including changing the very way the phone works.
Increased popularity of mobile worms and viruses would certainly have an impact on the GSM operator as well. Blocking certain phone numbers and making customers frustrated with any inability to make phone calls on infected handsets would direct cause a lost of revenue. The added possibility of installing a backdoor on the handset would also have an impact on the privacy of the users, as malicious hackers could easily use Bluetooth or GPRS to read the Phonebook, Calendar, any SMS messages, and download photos from the phone.
The recent attack of the newer Mabir worm shows not only that mobile viruses are a growing trend but also that mobile viruses are getting more sophisticated. Cabir used only Bluetooth to spread, whereas its successor Mabir.A uses both Bluetooth and MMS to replicate, which is quite an improvement. The worm also sends an MMS in a reply to any received SMS, which is clever technique to fool the user into installing the received application. However, besides interesting techniques such as this, overall the Mabir worm is still relatively simple and does not use any sophisticated attacks on specific application or system vulnerabilities. Compare this to the most dangerous worms affecting personal computers today, which tend to benefit from vulnerabilities in the PC's operating system or applications in order to propagate. This area has not yet been explored by the mobile virus writers. Could this be a future attack vector for a mobile viruses? This author believes it is quite possible, and that such an approach can even include vulnerabilities in Bluetooth related applications on mobile phones. To prove this point, let's look at some simple yet unpublished vulnerabilities that exist today.
computer networking theory
bluetooth zone
Bluetooth is a high-speed, low-power microwave wireless link technology, designed to connect phones, laptops, PDAs and other portable equipment together with little or no work by the user.
Bluetooth is the name for a short-range radio frequency (RF) technology that operates at 2.4 GHz and is capable of transmitting voice and data. The effective range of Bluetooth devices is 32 feet (10 meters). Bluetooth transfers data at the rate of 1 Mbps, which is from three to eight times the average speed of parallel and serial ports, respectively. It is also known as the IEEE 802.15 standards. It was invented to get rid of wires. Bluetooth is more suited for connecting two point-to-point devices, whereas Wi-Fi is an IEEE standard intended for networking.
When the Cabir mobile worm started to attack mobile devices and used Bluetooth to spread, many people were caught by surprise. It first appeared as a proof-of-concept virus written by the A29 group, was provided to an anti-virus company, and then later appeared in the wild. The worm started spreading from infected mobile phones using the Bluetooth wireless capabilities to search for the next victim and infect it based. This infection was based on a vulnerability in the Bluetooth implementation of several Nokia and Sony Ericsson phones. The virus was not dangerous, however, as it only drained the phone's battery and it still required the user to accept installation of the file. However, it showed that it is possible to write mobiles viruses that spread via Bluetooth, which may encourage a number of virus writers to take the same approach. Future Bluetooth viruses may very well be much more damaging. A good example of the potential damage that can be caused first appeared in Japan in 2001, where the virus blocked the ability to call emergency numbers. Recent vulnerabilities in Java, discovered by famous Polish security researcher Adam Gowdiak, could also be used by mobile virus writers to break the Java mobile security model and get access to the phone's memory, affecting many things including changing the very way the phone works.
Increased popularity of mobile worms and viruses would certainly have an impact on the GSM operator as well. Blocking certain phone numbers and making customers frustrated with any inability to make phone calls on infected handsets would direct cause a lost of revenue. The added possibility of installing a backdoor on the handset would also have an impact on the privacy of the users, as malicious hackers could easily use Bluetooth or GPRS to read the Phonebook, Calendar, any SMS messages, and download photos from the phone.
The recent attack of the newer Mabir worm shows not only that mobile viruses are a growing trend but also that mobile viruses are getting more sophisticated. Cabir used only Bluetooth to spread, whereas its successor Mabir.A uses both Bluetooth and MMS to replicate, which is quite an improvement. The worm also sends an MMS in a reply to any received SMS, which is clever technique to fool the user into installing the received application. However, besides interesting techniques such as this, overall the Mabir worm is still relatively simple and does not use any sophisticated attacks on specific application or system vulnerabilities. Compare this to the most dangerous worms affecting personal computers today, which tend to benefit from vulnerabilities in the PC's operating system or applications in order to propagate. This area has not yet been explored by the mobile virus writers. Could this be a future attack vector for a mobile viruses? This author believes it is quite possible, and that such an approach can even include vulnerabilities in Bluetooth related applications on mobile phones. To prove this point, let's look at some simple yet unpublished vulnerabilities that exist today.
computer networking theory
bluetooth zone
knoew the computer virus
A computer virus is an executable program. Depend on the nature of a virus, it may cause damage of your hard disk contents, and/or interfere normal operation of your computer.
By definition, a virus program is able to replicate itself. This means that the virus multiplies on a computer by making copies of itself. This replication is intentional; it is part of the virus program. In most cases, if a file that contains virus is executed or copied onto another computer, then that computer will also be "infected" by the same virus.
A virus can be introduced to a computer system along with any software program. For Internet users, this threat can come from downloading files through FTP (file transfer protocol), or referencing email attachments. (Please refer to our web page on Handling Email's File Attachments for details.)
When a virus is introduced to a computer system, it can attach itself to, or sometimes even replace, an existing program. Thus, when the user runs the program in question, the virus is also executed. This usually happens without the user being aware of it.
A virus program contains instructions to initiate some sort of "event" that affects the infected computer. Each virus
has an unique event associated with it. These events and their effects can range from harmless to devastating. For examples:
* An annoying message appearing on the computer screen.
* Reduced memory or disk space.
* Modification of data.
* Files overwritten or damaged.
* Hard drive erased.
computer science world
By definition, a virus program is able to replicate itself. This means that the virus multiplies on a computer by making copies of itself. This replication is intentional; it is part of the virus program. In most cases, if a file that contains virus is executed or copied onto another computer, then that computer will also be "infected" by the same virus.
A virus can be introduced to a computer system along with any software program. For Internet users, this threat can come from downloading files through FTP (file transfer protocol), or referencing email attachments. (Please refer to our web page on Handling Email's File Attachments for details.)
When a virus is introduced to a computer system, it can attach itself to, or sometimes even replace, an existing program. Thus, when the user runs the program in question, the virus is also executed. This usually happens without the user being aware of it.
A virus program contains instructions to initiate some sort of "event" that affects the infected computer. Each virus
has an unique event associated with it. These events and their effects can range from harmless to devastating. For examples:* An annoying message appearing on the computer screen.
* Reduced memory or disk space.
* Modification of data.
* Files overwritten or damaged.
* Hard drive erased.
computer science world
look at shortcuts
Accessibility Keyboard Shortcuts
1) Right SHIFT for eight seconds (Switch FilterKeys either on or off)
2) Left ALT+left SHIFT+PRINT SCREEN (Switch High Contrast either on or off)
3) Left ALT+left SHIFT+NUM LOCK (Switch the MouseKeys either on or off)
4) SHIFT five times (Switch the StickyKeys either on or off)
5) NUM LOCK for five seconds (Switch the ToggleKeys either on or off)
6) Windows Logo +U (Open Utility Manager)
Windows Explorer Keyboard Shortcuts
1) END (Display the bottom of the active window)
2) HOME (Display the top of the active window)
3) NUM LOCK+Asterisk sign (*) (Display all of the subfolders that are under the selected folder)
4) NUM LOCK+Plus sign (+) (Display the contents of the selected folder)
5) NUM LOCK+Minus sign (-) (Collapse the selected folder)
6) LEFT ARROW (Collapse the current selection if it is expanded, or select the parent folder)
7) RIGHT ARROW (Display the current selection if it is collapsed, or select the first subfolder)
Shortcut Keys for Character Map
After you double-click a character on the grid of characters, you can move through the grid by using the keyboard shortcuts:
1) RIGHT ARROW (Move to the right or to the beginning of the next line)
2) LEFT ARROW (Move to the left or to the end of the previous line)
3) UP ARROW (Move up one row)
4) DOWN ARROW (Move down one row)
5) PAGE UP (Move up one screen at a time)
6) PAGE DOWN (Move down one screen at a time)
7) HOME (Move to the beginning of the line)
8) END (Move to the end of the line)
9) CTRL+HOME (Move to the first character)
10) CTRL+END (Move to the last character)
11) SPACEBAR (Switch between Enlarged and Normal mode when a character is selected)
Microsoft Management Console (MMC) Main Window Keyboard Shortcuts
1) CTRL+O (Open a saved console)
2) CTRL+N (Open a new console)
3) CTRL+S (Save the open console)
4) CTRL+M (Add or remove a console item)
5) CTRL+W (Open a new window)
6) F5 key (Update the content of all console windows)
7) ALT+SPACEBAR (Display the MMC window menu)
8) ALT+F4 (Close the console)
9) ALT+A (Display the Action menu)
10) ALT+V (Display the View menu)
11) ALT+F (Display the File menu)
12) ALT+O (Display the Favorites menu)
13) MMC Console Window Keyboard Shortcuts
14) CTRL+P (Print the current page or active pane)
15) ALT+Minus sign (-) (Display the window menu for the active console window)
16) SHIFT+F10 (Display the Action shortcut menu for the selected item)
17) F1 key (Open the Help topic, if any, for the selected item)
18) F5 key (Update the content of all console windows)
19) CTRL+F10 (Maximize the active console window)
20) CTRL+F5 (Restore the active console window)
21) ALT+ENTER (Display the Properties dialog box, if any, for the selected item)
22) F2 key (Rename the selected item)
23) CTRL+F4 (Close the active console window. When a console has only one console window, this shortcut closes the console)
Remote Desktop Connection Navigation
1) CTRL+ALT+END (Open the m*cro$oft Windows NT Security dialog box)
2) ALT+PAGE UP (Switch between programs from left to right)
3) ALT+PAGE DOWN (Switch between programs from right to left)
4) ALT+INSERT (Cycle through the programs in most recently used order)
5) ALT+HOME (Display the Start menu)
6) CTRL+ALT+BREAK (Switch the client computer between a window and a full screen)
7) ALT+DELETE (Display the Windows menu)
8) CTRL+ALT+Minus sign (-) (Place a snapshot of the active window in the client on the Terminal server clipboard and provide the same functionality as pressing PRINT SCREEN on a local computer.)
9) CTRL+ALT+Plus sign (+) (Place a snapshot of the entire client window area on the Terminal server clipboard and provide the same functionality as pressing ALT+PRINT SCREEN on a local computer.)
Microsoft Internet Explorer Navigation
1) CTRL+B (Open the Organize Favorites dialog box)
2) CTRL+E (Open the Search bar)
3) CTRL+F (Start the Find utility)
4) CTRL+H (Open the History bar)
5) CTRL+I (Open the Favorites bar)
6) CTRL+L (Open the Open dialog box)
7) CTRL+N (Start another instance of the browser with the same Web address)
8) CTRL+O (Open the Open dialog box, the same as CTRL+L)
9) CTRL+P (Open the Print dialog box)
10) CTRL+R (Update the current Web page)
11) CTRL+W (Close the current window)
1) Right SHIFT for eight seconds (Switch FilterKeys either on or off)
2) Left ALT+left SHIFT+PRINT SCREEN (Switch High Contrast either on or off)
3) Left ALT+left SHIFT+NUM LOCK (Switch the MouseKeys either on or off)
4) SHIFT five times (Switch the StickyKeys either on or off)
5) NUM LOCK for five seconds (Switch the ToggleKeys either on or off)
6) Windows Logo +U (Open Utility Manager)
Windows Explorer Keyboard Shortcuts
1) END (Display the bottom of the active window)
2) HOME (Display the top of the active window)
3) NUM LOCK+Asterisk sign (*) (Display all of the subfolders that are under the selected folder)
4) NUM LOCK+Plus sign (+) (Display the contents of the selected folder)
5) NUM LOCK+Minus sign (-) (Collapse the selected folder)
6) LEFT ARROW (Collapse the current selection if it is expanded, or select the parent folder)
7) RIGHT ARROW (Display the current selection if it is collapsed, or select the first subfolder)
Shortcut Keys for Character Map
After you double-click a character on the grid of characters, you can move through the grid by using the keyboard shortcuts:
1) RIGHT ARROW (Move to the right or to the beginning of the next line)
2) LEFT ARROW (Move to the left or to the end of the previous line)
3) UP ARROW (Move up one row)
4) DOWN ARROW (Move down one row)
5) PAGE UP (Move up one screen at a time)
6) PAGE DOWN (Move down one screen at a time)
7) HOME (Move to the beginning of the line)
8) END (Move to the end of the line)
9) CTRL+HOME (Move to the first character)
10) CTRL+END (Move to the last character)
11) SPACEBAR (Switch between Enlarged and Normal mode when a character is selected)
Microsoft Management Console (MMC) Main Window Keyboard Shortcuts
1) CTRL+O (Open a saved console)
2) CTRL+N (Open a new console)
3) CTRL+S (Save the open console)
4) CTRL+M (Add or remove a console item)
5) CTRL+W (Open a new window)
6) F5 key (Update the content of all console windows)
7) ALT+SPACEBAR (Display the MMC window menu)
8) ALT+F4 (Close the console)
9) ALT+A (Display the Action menu)
10) ALT+V (Display the View menu)
11) ALT+F (Display the File menu)
12) ALT+O (Display the Favorites menu)
13) MMC Console Window Keyboard Shortcuts
14) CTRL+P (Print the current page or active pane)
15) ALT+Minus sign (-) (Display the window menu for the active console window)
16) SHIFT+F10 (Display the Action shortcut menu for the selected item)
17) F1 key (Open the Help topic, if any, for the selected item)
18) F5 key (Update the content of all console windows)
19) CTRL+F10 (Maximize the active console window)
20) CTRL+F5 (Restore the active console window)
21) ALT+ENTER (Display the Properties dialog box, if any, for the selected item)
22) F2 key (Rename the selected item)
23) CTRL+F4 (Close the active console window. When a console has only one console window, this shortcut closes the console)
Remote Desktop Connection Navigation
1) CTRL+ALT+END (Open the m*cro$oft Windows NT Security dialog box)
2) ALT+PAGE UP (Switch between programs from left to right)
3) ALT+PAGE DOWN (Switch between programs from right to left)
4) ALT+INSERT (Cycle through the programs in most recently used order)
5) ALT+HOME (Display the Start menu)
6) CTRL+ALT+BREAK (Switch the client computer between a window and a full screen)
7) ALT+DELETE (Display the Windows menu)
8) CTRL+ALT+Minus sign (-) (Place a snapshot of the active window in the client on the Terminal server clipboard and provide the same functionality as pressing PRINT SCREEN on a local computer.)
9) CTRL+ALT+Plus sign (+) (Place a snapshot of the entire client window area on the Terminal server clipboard and provide the same functionality as pressing ALT+PRINT SCREEN on a local computer.)
Microsoft Internet Explorer Navigation
1) CTRL+B (Open the Organize Favorites dialog box)
2) CTRL+E (Open the Search bar)
3) CTRL+F (Start the Find utility)
4) CTRL+H (Open the History bar)
5) CTRL+I (Open the Favorites bar)
6) CTRL+L (Open the Open dialog box)
7) CTRL+N (Start another instance of the browser with the same Web address)
8) CTRL+O (Open the Open dialog box, the same as CTRL+L)
9) CTRL+P (Open the Print dialog box)
10) CTRL+R (Update the current Web page)
11) CTRL+W (Close the current window)
wireless internrt connection
Wireless Internet access, sometimes referred to as a "hot spot," is a local area network (LAN) run by radio waves rather than wires. Wireless Internet access is broadcast from a central hub, which is a hard-wired device that actually brings in the Internet connection. The hub, located at the main computer system or server, broadcasts Internet connectivity to clients, which is basically anyone within receiving range who is equipped with a wireless LAN card.
do you know about open source?
In the home, a desktop system setup for wireless Internet access will broadcast connectivity throughout the immediate area. Any family member with a laptop or desktop in another room can connect wirelessly to the Internet to share the main connection. Neighbors may also be able to access this wireless connection, which is why most wireless LANs are configured with password security. In this case, any machine that wishes to get wireless Internet access must first complete a "handshake" with the LAN, in which the password is requested. If the proper password is not supplied, access is denied. Security protocols for wireless Internet access have improved with Wi Fi Protected Access (WPA) and Wi Fi Protected Access 2 (WPA2) options.
what is backtrack?
While wireless Internet access is very convenient in the home, it can be even more so in the workplace. A wired network can not only be very time consuming to install throughout a building, it is also very expensive. Ethernet cables used to connect client machines might need to be routed through walls, ceilings, and floors. In the past, this disadvantage was sometimes overlooked due to the advantages of greater security and faster data transfer speeds through Ethernet cables.
These advantages have been largely mitigated, however. Wireless LANs can be installed in virtually minutes by nearly anyone, are extremely inexpensive, and can have data transfer rates that rival hard-wired Ethernet LANs. Furthermore, WPA2 encrypts all traffic on the LAN, addressing the problem of eavesdropping.
One of the most popular applications for wireless Internet access is the public hot spot. Internet cafes are one example of places where one can sit with a laptop and sip coffee while cruising the Internet, checking email, or doing research. Cell phones and personal digital assistants (PDAs) equipped with Web browsers can also utilize wireless Internet access points through public hot spots.
Some localities provide free wireless Internet access for residents and visitors. Since wireless LANs use radio waves that distort over long distances, the radius of the signal is limited. The further from the hub, the weaker the signal. Therefore cities that provide access will cover a specific area within the city where people can park to gain access.
Technology for wireless LANs is improving constantly. When designing a new wireless network, the person setting up the network should be sure to get network cards, a hub, and a wireless modem that support the latest protocols and security measures. Instructions should be followed carefully when configuring wireless Internet access.
Networking allows two or more computers to interface with each other, whether in an office, a library or other type of establishment, or at home. Running cables throughout an office or a house can be tedious and time-consuming, however, making wireless networking - a network of interfaced computers that doesn't require any hardwired connection between the computers - the ideal choice for many businesses and homes.
Wireless networking has many uses. Wireless networking at an office or place of business makes it easy to share files, printers, and Internet access between all of the computers. Wireless networking at home or in a home office can enable you to print a file from your laptop without having to go to the printer and hook up to it. Wireless networking also means that you can take your laptop to a place that offers WiFi, known as a "hotspot," and instantly connect to the Internet - a valuable tool for businesspeople, entrepreneurs, and students.
For wireless networking to be possible, all computers connected to the network must have a wireless card. Wireless networking is virtually the same thing as wireless Internet access - except instead of connecting to the Internet, you are connecting to another computer - so if you can already access the Internet wirelessly, wireless networking will be just as easy. Many of the newer laptops on the market come fully equipped for wireless networking, and you can buy a wireless card to upgrade your computer if it doesn't already have wireless networking capabilities.
There are several different kinds of wireless cards available. The first cards on the market were 802.11b, but the standard was eventually upgraded to 802.11g. The latter type of card, being the newest, also has the fastest data transfer, making it the obvious choice for anyone who is serious about wireless networking.
Wireless networking and wireless Internet access may seem dangerous to some people. If the channel is left open, anyone can log on to the network; once on the network, that person could hack into one of the other computers, easily locating personal files containing sensitive information. However, what many people don't realize is that wireless networking and wireless Internet access comes with a feature that protects against such an event: the WEP key. The WEP key is essentially a password that is required before a computer can sign on to the wireless network, which prevents any unauthorized use. If you are unsure of how to set up this feature, you can call the provider of your wireless service or the manufacturer of your wireless modem or router.
do you know about open source?
In the home, a desktop system setup for wireless Internet access will broadcast connectivity throughout the immediate area. Any family member with a laptop or desktop in another room can connect wirelessly to the Internet to share the main connection. Neighbors may also be able to access this wireless connection, which is why most wireless LANs are configured with password security. In this case, any machine that wishes to get wireless Internet access must first complete a "handshake" with the LAN, in which the password is requested. If the proper password is not supplied, access is denied. Security protocols for wireless Internet access have improved with Wi Fi Protected Access (WPA) and Wi Fi Protected Access 2 (WPA2) options.
what is backtrack?
While wireless Internet access is very convenient in the home, it can be even more so in the workplace. A wired network can not only be very time consuming to install throughout a building, it is also very expensive. Ethernet cables used to connect client machines might need to be routed through walls, ceilings, and floors. In the past, this disadvantage was sometimes overlooked due to the advantages of greater security and faster data transfer speeds through Ethernet cables.
These advantages have been largely mitigated, however. Wireless LANs can be installed in virtually minutes by nearly anyone, are extremely inexpensive, and can have data transfer rates that rival hard-wired Ethernet LANs. Furthermore, WPA2 encrypts all traffic on the LAN, addressing the problem of eavesdropping.
One of the most popular applications for wireless Internet access is the public hot spot. Internet cafes are one example of places where one can sit with a laptop and sip coffee while cruising the Internet, checking email, or doing research. Cell phones and personal digital assistants (PDAs) equipped with Web browsers can also utilize wireless Internet access points through public hot spots.
Some localities provide free wireless Internet access for residents and visitors. Since wireless LANs use radio waves that distort over long distances, the radius of the signal is limited. The further from the hub, the weaker the signal. Therefore cities that provide access will cover a specific area within the city where people can park to gain access.
Technology for wireless LANs is improving constantly. When designing a new wireless network, the person setting up the network should be sure to get network cards, a hub, and a wireless modem that support the latest protocols and security measures. Instructions should be followed carefully when configuring wireless Internet access.
Networking allows two or more computers to interface with each other, whether in an office, a library or other type of establishment, or at home. Running cables throughout an office or a house can be tedious and time-consuming, however, making wireless networking - a network of interfaced computers that doesn't require any hardwired connection between the computers - the ideal choice for many businesses and homes.
Wireless networking has many uses. Wireless networking at an office or place of business makes it easy to share files, printers, and Internet access between all of the computers. Wireless networking at home or in a home office can enable you to print a file from your laptop without having to go to the printer and hook up to it. Wireless networking also means that you can take your laptop to a place that offers WiFi, known as a "hotspot," and instantly connect to the Internet - a valuable tool for businesspeople, entrepreneurs, and students.
For wireless networking to be possible, all computers connected to the network must have a wireless card. Wireless networking is virtually the same thing as wireless Internet access - except instead of connecting to the Internet, you are connecting to another computer - so if you can already access the Internet wirelessly, wireless networking will be just as easy. Many of the newer laptops on the market come fully equipped for wireless networking, and you can buy a wireless card to upgrade your computer if it doesn't already have wireless networking capabilities.
There are several different kinds of wireless cards available. The first cards on the market were 802.11b, but the standard was eventually upgraded to 802.11g. The latter type of card, being the newest, also has the fastest data transfer, making it the obvious choice for anyone who is serious about wireless networking.
Wireless networking and wireless Internet access may seem dangerous to some people. If the channel is left open, anyone can log on to the network; once on the network, that person could hack into one of the other computers, easily locating personal files containing sensitive information. However, what many people don't realize is that wireless networking and wireless Internet access comes with a feature that protects against such an event: the WEP key. The WEP key is essentially a password that is required before a computer can sign on to the wireless network, which prevents any unauthorized use. If you are unsure of how to set up this feature, you can call the provider of your wireless service or the manufacturer of your wireless modem or router.
antivirus working concepts
How does anti-virus software work?
An anti-virus software program is a computer program that can be used to scan files to identify and eliminate computer viruses and other malicious software (malware).
Anti-virus software typically uses two different techniques to accomplish this:
* Examining files to look for known viruses by means of a virus dictionary
* Identifying suspicious behavior from any computer program which might indicate infection
Most commercial anti-virus software uses both of these approaches, with an emphasis on the virus dictionary approach.
Virus dictionary approach
In the virus dictionary approach, when the anti-virus software examines a file, it refers to a dictionary of known viruses that have been identified by the author of the anti-virus software. If a piece of code in the file matches any virus identified in the dictionary, then the anti-virus software can then either delete the file, quarantine it so that the file is inaccessible to other programs and its virus is unable to spread, or attempt to repair the file by removing the virus itself from the file.
To be successful in the medium and long term, the virus dictionary approach requires periodic online downloads of updated virus dictionary entries. As new viruses are identified "in the wild", civically minded and technically inclined users can send their infected files to the authors of anti-virus software, who then include information about the new viruses in their dictionaries.
Dictionary-based anti-virus software typically examines files when the computer's operating system creates, opens, and closes them; and when the files are e-mailed. In this way, a known virus can be detected immediately upon receipt. The software can also typically be scheduled to examine all files on the user's hard disk on a regular basis.
Although the dictionary approach is considered effective, virus authors have tried to stay a step ahead of such software by writing "polymorphic viruses", which encrypt parts of themselves or otherwise modify themselves as a method of disguise, so as to not match the virus's signature in the dictionary.
Suspicious behavior approach
The suspicious behavior approach, by contrast, doesn't attempt to identify known viruses, but instead monitors the behavior of all programs. If one program tries to write data to an executable program, for example, this is flagged as suspicious behavior and the user is alerted to this, and asked what to do.
Unlike the dictionary approach, the suspicious behavior approach therefore provides protection against brand-new viruses that do not yet exist in any virus dictionaries. However, it also sounds a large number of false positives, and users probably become desensitized to all the warnings. If the user clicks "Accept" on every such warning, then the anti-virus software is obviously useless to that user. This problem has especially been made worse over the past 7 years, since many more nonmalicious program designs chose to modify other .exes without regards to this false positive issue. Thus, most modern anti virus software uses this technique less and less.
Other ways to detect viruses
Some antivirus-software will try to emulate the beginning of the code of each new executable that is being executed before transferring control to the executable. If the program seems to be using self-modifying code or otherwise appears as a virus (it immeadeatly tries to find other executables), one could assume that the executable has been infected with a virus. However, this method results in a lot of false positives.
Yet another detection method is using a sandbox. A sandbox emulates the operating system and runs the executable in this simulation. After the program has terminated, the sandbox is analysed for changes which might indicate a virus. Because of performance issues this type of detection is normally only performed during on-demand scans.
Issues of concern
Macro viruses, arguably the most destructive and widespread computer viruses, could be prevented far more inexpensively and effectively, and without the need of all users to buy anti-virus software, if Microsoft would fix security flaws in Microsoft Outlook and Microsoft Office related to the execution of downloaded code and to the ability of document macros to spread and wreak havoc.
User education is as important as anti-virus software; simply training users in safe computing practices, such as not downloading and executing unknown programs from the Internet, would slow the spread of viruses, without the need of anti-virus software.
Computer users should not always run with administrator access to their own machine. If they would simply run in user mode then some types of viruses would not be able to spread.
The dictionary approach to detecting viruses is often insufficient due to the continual creation of new viruses, yet the suspicious behavior approach is ineffective due to the false positive problem; hence, the current understanding of anti-virus software will never conquer computer viruses.
There are various methods of encrypting and packing malicious software which will make even well-known viruses undetectable to anti-virus software. Detecting these "camouflaged" viruses requires a powerful unpacking engine, which can decrypt the files before examining them. Unfortunately, many popular anti-virus programs do not have this and thus are often unable to detect encrypted viruses.
Companies that sell anti-virus software seem to have a financial incentive for viruses to be written and to spread, and for the public to panic over the thr
An anti-virus software program is a computer program that can be used to scan files to identify and eliminate computer viruses and other malicious software (malware).
Anti-virus software typically uses two different techniques to accomplish this:
* Examining files to look for known viruses by means of a virus dictionary
* Identifying suspicious behavior from any computer program which might indicate infection
Most commercial anti-virus software uses both of these approaches, with an emphasis on the virus dictionary approach.
Virus dictionary approach
In the virus dictionary approach, when the anti-virus software examines a file, it refers to a dictionary of known viruses that have been identified by the author of the anti-virus software. If a piece of code in the file matches any virus identified in the dictionary, then the anti-virus software can then either delete the file, quarantine it so that the file is inaccessible to other programs and its virus is unable to spread, or attempt to repair the file by removing the virus itself from the file.
To be successful in the medium and long term, the virus dictionary approach requires periodic online downloads of updated virus dictionary entries. As new viruses are identified "in the wild", civically minded and technically inclined users can send their infected files to the authors of anti-virus software, who then include information about the new viruses in their dictionaries.
Dictionary-based anti-virus software typically examines files when the computer's operating system creates, opens, and closes them; and when the files are e-mailed. In this way, a known virus can be detected immediately upon receipt. The software can also typically be scheduled to examine all files on the user's hard disk on a regular basis.
Although the dictionary approach is considered effective, virus authors have tried to stay a step ahead of such software by writing "polymorphic viruses", which encrypt parts of themselves or otherwise modify themselves as a method of disguise, so as to not match the virus's signature in the dictionary.
Suspicious behavior approach
The suspicious behavior approach, by contrast, doesn't attempt to identify known viruses, but instead monitors the behavior of all programs. If one program tries to write data to an executable program, for example, this is flagged as suspicious behavior and the user is alerted to this, and asked what to do.
Unlike the dictionary approach, the suspicious behavior approach therefore provides protection against brand-new viruses that do not yet exist in any virus dictionaries. However, it also sounds a large number of false positives, and users probably become desensitized to all the warnings. If the user clicks "Accept" on every such warning, then the anti-virus software is obviously useless to that user. This problem has especially been made worse over the past 7 years, since many more nonmalicious program designs chose to modify other .exes without regards to this false positive issue. Thus, most modern anti virus software uses this technique less and less.
Other ways to detect viruses
Some antivirus-software will try to emulate the beginning of the code of each new executable that is being executed before transferring control to the executable. If the program seems to be using self-modifying code or otherwise appears as a virus (it immeadeatly tries to find other executables), one could assume that the executable has been infected with a virus. However, this method results in a lot of false positives.
Yet another detection method is using a sandbox. A sandbox emulates the operating system and runs the executable in this simulation. After the program has terminated, the sandbox is analysed for changes which might indicate a virus. Because of performance issues this type of detection is normally only performed during on-demand scans.
Issues of concern
Macro viruses, arguably the most destructive and widespread computer viruses, could be prevented far more inexpensively and effectively, and without the need of all users to buy anti-virus software, if Microsoft would fix security flaws in Microsoft Outlook and Microsoft Office related to the execution of downloaded code and to the ability of document macros to spread and wreak havoc.
User education is as important as anti-virus software; simply training users in safe computing practices, such as not downloading and executing unknown programs from the Internet, would slow the spread of viruses, without the need of anti-virus software.
Computer users should not always run with administrator access to their own machine. If they would simply run in user mode then some types of viruses would not be able to spread.
The dictionary approach to detecting viruses is often insufficient due to the continual creation of new viruses, yet the suspicious behavior approach is ineffective due to the false positive problem; hence, the current understanding of anti-virus software will never conquer computer viruses.
There are various methods of encrypting and packing malicious software which will make even well-known viruses undetectable to anti-virus software. Detecting these "camouflaged" viruses requires a powerful unpacking engine, which can decrypt the files before examining them. Unfortunately, many popular anti-virus programs do not have this and thus are often unable to detect encrypted viruses.
Companies that sell anti-virus software seem to have a financial incentive for viruses to be written and to spread, and for the public to panic over the thr
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