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I-Terms
Snooping protocol: Also referred to as a bus-snooping protocol, a protocol for maintaining cache coherency in symmetric multiprocessing environments. In a snooping system, all caches on the bus monitor (or snoop) the bus to determine if they have a copy of the block of data that is requested on the bus. Every cache has a copy of the sharing status of every block of physical memory it has. Multiple copies of a document in a multiprocessing environment typically can be read without any coherence problems; however, a processor must have exclusive access to the bus in order to write.
There are two types of snooping protocol:
(1) Write-invalidate: the processor that is writing data causes copies in the caches of all other processors in the system to be rendered invalid before it changes its local copy. The local machine does this by sending an invalidation signal over the bus, which causes all of the other caches to check for a copy of the invalidated file. Once the cache copies have been invalidated, the data on the local machine can be updated until another processor requests it.
(2) Write-update: the processor that is writing the data broadcasts the new data over the bus (without issuing the invalidation signal). All caches that contain copies of the data are then updated. This scheme differs from write-invalidate in that it does not create only one local copy for writes.
rDNS: Short for reverse DNS, a method of name resolution in which an IP address is resolved into a domain name, which is the opposite of the typical resolution method of DNS, which resolves domain names into IP addresses. One practical application of reverse DNS is as an anti-spam measure. Because spammers often use invalid IP addresses to send e-mails, rDNS will determine the authenticity of a domain name compared to the IP address from which it is originating.
Social engineering: In the realm of computers, the act of obtaining or attempting to obtain otherwise secure data by conning an individual into revealing secure information. Social engineering is successful because its victims innately want to trust other people and are naturally helpful. The victims of social engineering are tricked into releasing information that they do not realize will be used to attack a computer network. For example, an employee in an enterprise may be tricked into revealing an employee identification number to someone who is pretending to be someone he trusts or representing someone he trusts. While that employee number may not seem valuable to the employee, which makes it easier for him to reveal the information in the first place, the social engineer can use that employee number in conjunction with other information that has been gathered to get closer to finding a way into the enterprise’s network.
Phishing is a type of security attack that relies on social engineering in that it lures the victim into revealing information based on the human tendency to believe in the security of a brand name because they associate the brand name with trustworthiness.
VPI: Short for virtual path identifier, an eight-bit field in an ATM cell’s header that identifies the virtual path (a bundle of virtual channels that have the same endpoint) to which the cell belongs as it travels through an ATM network. An ATM switch uses either the VPI, the VCI, or a combination of both to route the cell to its destination.
VCI: Short for virtual channel identifier is a 16-bit field in an ATM cell’s header that identifies the cell’s next destination as it travels through an ATM network (also see VPI above).
DTCP-IP: Short for Digital Transmission Content Protection over Internet Protocol, a specification for copy protection of copyrighted content that is transferred over digital interfaces in home networks that adhere to IP. Under this specification, digital content can be shared securely between devices in a user’s home but not shared with third-parties outside the home network. Using an authentication scheme, DTCP-IP allows the user to designate devices in the home network as trusted destinations that can transfer data back and forth, but DTCP-IP will not allow the content to be transmitted over the Internet to be shared outside of the home network.
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