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Network+ Guide to Networks, Fourth Edition. Chapter 13 Ensuring Integrity and Availability. What Are Integrity and Availability?. Integrity: soundness of network’s programs, data, services, devices, and connections

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Network+ Guide to Networks, Fourth Edition

Chapter 13

Ensuring Integrity and Availability


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What Are Integrity and Availability?

  • Integrity: soundness of network’s programs, data, services, devices, and connections

  • Availability: how consistently and reliably file or system can be accessed by authorized personnel

    • Need well-planned and well-configured network

    • Data backups, redundant devices, protection from malicious intruders

  • Phenomena compromising integrity and availability:

    • Security breaches, natural disasters, malicious intruders, power flaws, human error

Network+ Guide to Networks, 4e


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Viruses

  • Program that replicates itself with intent to infect more computers

    • Through network connections or exchange of external storage devices

    • Typically copied to storage device without user’s knowledge

  • Trojan horse: program that disguises itself as something useful but actually harms system

    • Not considered a virus

Network+ Guide to Networks, 4e


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Types of Viruses

  • Boot sector viruses:located in boot sector of computer’s hard disk

    • When computer boots up, virus runs in place of computer’s normal system files

    • Removal first requires rebooting from uninfected, write-protected disk with system files on it

  • Macro viruses:take form of macro that may be executed as user works with a program

    • Quick to emerge and spread

    • Symptoms vary widely

Network+ Guide to Networks, 4e


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Types of Viruses (continued)

  • File-infected viruses: attach to executable files

    • When infected executable file runs, virus copies itself to memory

    • Can have devastating consequences

    • Symptoms may include damaged program files, inexplicable file size increases, changed icons for programs, strange messages, inability to run a program

  • Worms: programs that run independently and travel between computers and across networks

    • Not technically viruses

    • Can transport and hide viruses

Network+ Guide to Networks, 4e


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Types of Viruses (continued)

  • Trojan horse: program that claims to do something useful but instead harms system

  • Network viruses: propagated via network protocols, commands, messaging programs, and data links

  • Bots: program that runs automatically, without requiring a person to start or stop it

    • Many bots spread through Internet Relay Chat (IRC)

    • Used to damage/destroy data or system files, issue objectionable content, further propagate virus

Network+ Guide to Networks, 4e


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Virus Characteristics

  • Encryption: encrypted virus may thwart antivirus program’s attempts to detect it

  • Stealth: stealth viruses disguise themselves as legitimate programs or replace part of legitimate program’s code with destructive code

  • Polymorphism: polymorphic viruses change characteristics every time transferred

  • Time-dependence: time-dependent viruses programmed to activate on particular date

Network+ Guide to Networks, 4e


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Virus Protection: Antivirus Software

  • Antivirus software should at least:

    • Detect viruses through signature scanning

    • Detect viruses through integrity checking

    • Detect viruses by monitoring unexpected file changes or virus-like behaviors

    • Receive regular updates and modifications from a centralized network console

    • Consistently report only valid viruses

      • Heuristic scanning techniques attempt to identify viruses by discovering “virus-like” behavior (may give “false positives”)

Network+ Guide to Networks, 4e


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Antivirus Policies

  • Provide rules for using antivirus software and policies for installing programs, sharing files, and using floppy disks

  • Suggestions for antivirus policy guidelines:

    • Every computer in organization equipped with virus detection and cleaning software

    • Users should not be allowed to alter or disable antivirus software

    • Users should know what to do in case virus detected

Network+ Guide to Networks, 4e


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Fault Tolerance

  • Capacity for system to continue performing despite unexpected hardware or software malfunction

  • Failure: deviation from specified level of system performance for given period of time

  • Fault: involves malfunction of system component

    • Can result in a failure

  • Varying degrees

    • At highest level, system remains unaffected by even most drastic problems

Network+ Guide to Networks, 4e


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Power: Power Flaws

  • Power flaws that can damage equipment:

    • Surge: momentary increase in voltage due to lightning strikes, solar flares, or electrical problems

    • Noise: fluctuation in voltage levels caused by other devices on network or electromagnetic interference

    • Brownout: momentary decrease in voltage; also known as a sag

    • Blackout: complete power loss

Network+ Guide to Networks, 4e


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UPSs (Uninterruptible Power Supplies)

  • Battery-operated power source directly attached to one or more devices and to power supply

    • Prevents undesired features of outlet’s A/C power from harming device or interrupting services

    • Standby UPS: provides continuous voltage to device

      • Switch to battery when power loss detected

    • Online UPS: uses power from wall outlet to continuously charge battery, while providing power to network device through battery

Network+ Guide to Networks, 4e


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Servers

  • Make servers more fault-tolerant by supplying them with redundant components

    • NICs, processors, and hard disks

    • If one item fails, entire system won’t fail

    • Enable load balancing

Network+ Guide to Networks, 4e


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Server Mirroring

  • Mirroring: one device or component duplicates activities of another

  • Server Mirroring: one server duplicates transactions and data storage of another

    • Must be identical machines using identical components

    • Requires high-speed link between servers

    • Requires synchronization software

    • Form of replication

  • Servers can stand side by side or be positioned in different locations

Network+ Guide to Networks, 4e


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Clustering

  • Link multiple servers together to act as single server

    • Share processing duties

    • Appear as single server to users

    • If one server fails, others automatically take over data transaction and storage responsibilities

    • More cost-effective than mirroring

    • To detect failures, clustered servers regularly poll each other

    • Servers must be close together

Network+ Guide to Networks, 4e


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Storage: RAID (Redundant Array of Independent (or Inexpensive) Disks)

  • Collection of disks that provide fault tolerance for shared data and applications

    • Disk array

    • Collection of disks that work together in RAID configuration, often referred to as RAID drive

      • Appear as single logical drive to system

  • Hardware RAID: set of disks and separate disk controller

    • Managed exclusively by RAID disk controller

  • Software RAID: relies on software to implement and control RAID techniques

Network+ Guide to Networks, 4e


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RAID Level 0 Inexpensive) Disks)―Disk Striping

  • Simple implementation of RAID

    • Not fault-tolerant

    • Improves performance

Figure 13-6: RAID Level 0—disk striping

Network+ Guide to Networks, 4e


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RAID Level 1—Disk Mirroring Inexpensive) Disks)

  • Data from one disk copied to another disk automatically as information written

    • Dynamic backup

    • If one drive fails, disk array controller automatically switches to disk that was mirroring it

    • Requires two identical disks

    • Usually relies on system software to perform mirroring

  • Disk duplexing: similar to disk mirroring, but separate disk controller used for each disk

Network+ Guide to Networks, 4e


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RAID Level 1—Disk Mirroring (continued) Inexpensive) Disks)

Figure 13-7: RAID Level 1—disk mirroring

Network+ Guide to Networks, 4e


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RAID Level 5—Disk Striping with Distributed Parity Inexpensive) Disks)

  • Data written in small blocks across several disks

    • Parity error checking information distributed among disks

    • Highly fault-tolerant

    • Very popular

    • Failed disk can be replaced with little interruption

  • Hot spare: disk or partition that is part of array, but used only in case a RAID disks fails

  • Cold spare: duplicate component that can be installed in case of failure

Network+ Guide to Networks, 4e


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RAID Level 5—Disk Striping with Distributed Parity (continued)

Figure 13-9: RAID Level 5—disk striping with distributed parity

Network+ Guide to Networks, 4e


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NAS (Network Attached Storage) (continued)

  • Specialized storage device that provides centralized fault-tolerant data storage

    • Maintains own interface to LAN

    • Contains own file system optimized for saving and serving files

    • Easily expanded without interrupting service

    • Cannot communicate directly with network clients

Network+ Guide to Networks, 4e


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NAS (continued) (continued)

Figure 13-10: Network attached storage on a LAN

Network+ Guide to Networks, 4e


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SANs (Storage Area Networks) (continued)

Figure 13-11: A storage area network

Network+ Guide to Networks, 4e


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Data Backup (continued)

  • Copy of data or program files created for archiving or safekeeping

    • No matter how reliable and fault-tolerant you believe your server’s hard disk (or disks) to be, still risk losing everything unless you make backups on separate media and store them off-site

  • Many options exist for making backups

Network+ Guide to Networks, 4e


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Optical Media (continued)

  • Capable of storing digitized data

    • Uses laser to write and read data

    • CD-ROMs and DVDs

  • Requires proper disk drive to write data

  • Writing data usually takes longer than saving data to another type of media

Network+ Guide to Networks, 4e


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External Disk Drives (continued)

  • Storage devices that can be attached temporarily to a computer via USB, PCMCIA, FireWire, or Compact-Flash port

    • Removable disk drives

  • For backing up large amounts of data, likely to use external disk drive with backup control features, high capacity, and fast read-write access

  • Faster data transfer rates than optical media or tape backups

Network+ Guide to Networks, 4e


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Backup Strategy (continued) (continued)

  • Archive bit: file attribute that can be checked or unchecked

    • Indicates whether file must be archived

  • Backup methods use archive bit in different ways

    • Full backup: all data copied to storage media, regardless of whether data is new or changed

      • Archive bits set to “off” for all files

    • Incremental backup: copies only data that has changed since last full or incremental backup

      • Unchecks archive bit for every file saved

    • Differential backup:does not uncheck archive bits for files backed up

Network+ Guide to Networks, 4e


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Disaster Recovery: (continued)Disaster Recovery Planning

  • Disaster recovery: process of restoring critical functionality and data after enterprise-wide outage

  • Disaster recovery plan accounts for worst-case scenarios

    • Contact names and info for emergency coordinators

    • Details on data and servers being backed up, backup frequency, backup location, how to recover

    • Details on network topology, redundancy, and agreements with national service carriers

    • Strategies for testing disaster recovery plan

    • Plan for managing the crisis

Network+ Guide to Networks, 4e


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Disaster Recovery Contingencies (continued)

  • Several options for recovering from disaster

    • Cold site: place where computers, devices, and connectivity necessary to rebuild network exist

      • Not configured, updated, or connected

    • Warm site: same as cold site, but some computers and devices appropriately configured, updated, or connected

    • Hot site: computers, devices, and connectivity necessary to rebuild network are appropriately configured, updated, and connected to match network’s current state

Network+ Guide to Networks, 4e


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