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Xuất phát từ hoạt động thực tiễn về phòng, chống và khắc phục hậu quả của virus máy tính, việc tìm hiểu các định nghĩa và phân loại virus máy tính là rất quan trọng. Sau đây là quan điểm của NIST-National Institute of Standart and Technology (Viện tiêu chuẩn - công nghệ quốc gia Hoa kỳ) về định nghĩa và phân loại trong lĩnh vực “virus máy tính”.
Some monumental breakthroughs have taken place in optical fiber cables
and their ability to bend around sharp corners without increasing attenuation
– but today’s technicians and installers may be receiving mixed messages. This
paper will highlight the potential issues surrounding these new fibers as they
apply to the people who handle and install the cables in fiber-to-the-premise
.CompTIA SY0-201: Practice Exam QUESTION NO: 1 Who is responsible for establishing access permissions to network resources in the DAC access control model? A. The system administrator. B. The owner of the resource. C. The system administrator and the owner of the resource. D. The user requiring access to the resource.
The Open Shortest Path First (OSPF) protocol is a link state protocol that handles routing
for IP traffic. Its newest implementation, version 2, which is explained in RFC 2328, is an
open standard, like RIP. Chapter 9 offered a brief introduction to link state protocols. As
you will see in this section, OSPF draws heavily on the concepts described in that chapter,
but it also has some features of its own. Besides covering the characteristics of OSPF, you’ll
be presented with enough information to undertake a very basic routing configuration
Discuss the IList interface with regards to classes that represent an ordered
collection of objects that can be individually indexed. Use the ArrayList
demonstration to reinforce this concept.
Discuss the IDictionary interface and the classes that it implements. Use
the Hashtable demonstration to show how to use the IDictionary interface.
Provide guidelines to help students distinguish between collections and
arrays, and explain when collections are used.
Discuss runtime casting for type safety and the effects of runtime casting,
and boxing and unboxing on performance.
The economic advantages of packet voice are driving both the access and core
voice networks away from circuit switching towards packet. The industry
continues to debate whether the future of these packet networks will be based on
pure ATM, pure Internet protocol (IP), IP over asynchronous transfer mode
(ATM), IP over multiprotocol label switching (MPLS), or a combination thereof.
There are advantages to both ATM and IP and reasons for choosing each.
This chapter addresses what most people think about when they start to secure a
router—authenticating users and restricting access. There are many more ways to
access Cisco routers than most network administrators realize. Each of these methods
can have different authentication methods and can be set to allow various levels
of privilege access. It is important that all methods of access are either secured or disabled.
All versions of Unix work with alphanumeric terminals that handle a single
session in a single screen, such as those described in Chapter 1. On
most modern Unix versions, you can also use a window system. A window
system is software that lets a single screen handle many sessions at once.*
Window systems use a mouse or another device (such as a trackball) to
move a pointer acr oss the screen. The pointer can be used to select and
move parts of the screen, copy and paste text, work with menus of commands,
Two protocols support connection to the Internet via modem: SLIP (Serial Line Internet
Protocol) and PPP (Point to Point Protocol). As the name suggests, SLIP supports only
IP. It is an older, less rugged protocol. Its only advantage is that it may be available
where PPP isn’t. If you have the choice, always take PPP: it differs from SLIP in being
able to handle multiple protocols simultaneously, and it’s also used on many DSL links
(PPP over Ethernet or PPPoE). In this chapter, we’ll look only at PPP....
A major feature of the .NET Framework common language runtime is that the
runtime automatically handles the allocation and release of an objects memory
resources. In most cases, automatic memory management enhances code quality
and developer productivity without negatively impacting expressiveness or
The Adaptive Security Algorithm (ASA), used by the PIX Firewall for stateful application inspection,
ensures the secure use of applications and services. Some applications require special handling by the
PIX Firewall application inspection function. Applications that require special application inspection
functions are those that embed IP addressing information in the user data packet or open secondary
channels on dynamically assigned ports.
One of the most important parts of running any computer system is handling data on disk.
We have already looked at UNIX file handling in Chapter 10. In this chapter, we’ll look
at two ways to add another disk to your system, and what you should put on them. In
addition, we’ll discuss disk error recovery on page 218.
ADC’s family of singlemode reduced bend radius optical fiber patch cords have a bend radius
that is half that of standard singlemode patch cords without changing attenuation characteristics
of the cable. Designed for uses that range from the central office to FTTX deployments to OEM
applications, reduced bend radius cables are best suited for environments where there is increased
handling and movement of cables or where space is tight.
Today’s optical distribution frame (ODF) systems are already required to handle
more fiber than ever before, but as bandwidth requirements skyrocket, the need
for even higher fiber density continues to increase. Manufacturers are scrambling
to develop higher-density equipment and systems that can accommodate higher
and higher numbers of terminations in smaller and smaller areas.
When students move from the lecture hall to the microbiology
laboratory, they need help bridging the
gap between the theory and the practice of what they are
learning. The equipment is unfamiliar, the procedures
are unfamiliar, and many of the materials they are handling
are unfamiliar. Linking the information from their
classroom lectures to the laboratory procedures is necessary
for their ultimate success. Our goal for this
laboratory manual is to provide the bridge that helps
students integrate their classroom lectures with their
A second cell site was installed behind the right-field grandstand. The macro site would handle the
majority of the traffic. The new site would manage overflow and address coverage holes. Unfortunately,
the RF signal required transport to reach some obstructed areas, as well as the grandstand, where
additional capacity was necessary.
Passwords are the core of Cisco routers’ access control methods. Chapter 3
addressed basic access control and using passwords locally and from access control
servers. This chapter talks about how Cisco routers store passwords, how important
it is that the passwords chosen are strong passwords, and how to make sure that
your routers use the most secure methods for storing and handling passwords. It
then discusses privilege levels and how to implement them.
Incident management capabilities1 can take many forms—they can be an ad hoc group that is
pulled together in a crisis, they can be a defined set of procedures that are followed when an
incident occurs, or they can be a designated group of people assigned explicit responsibility
for handling computer security incidents, generically called a computer security incident response
team, or CSIRT.2
In our work, we are often asked for a “roadmap” or set of processes and templates that can be
used by an organization to guide the development of their incident management capability.
Perimeter security solutions control access to critical network applications, data, and services so that only legitimate users
and information can pass through the network. This access control is handled by routers and switches with access control
lists (ACLs) and by dedicated ﬁrewall appliances. A ﬁrewall provides a barrier to trafﬁc crossing a network’s “perimeter”
and permits only authorized trafﬁc to pass, according to a predeﬁned security policy. Complementary tools, including virus
scanners and content ﬁlters, also help control network perimeters.