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Chapter 13: Ensuring Integrity and Availability
Network+ Guide to Networks
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Objectives:
Identify the characteristics of a network that keep data safe from loss or damage
Protect an enterprise-wide network from viruses
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Objectives: (continued)
Explain network- and system-level fault-tolerance techniques
Discuss issues related to network backup and recovery strategies
Describe the components of a useful disaster recovery plan
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What are Integrity and Availability?
• Integrity refers to the soundness of a network’s programs, data, services, devices, and connections.
• Availability of a file or system refers to how consistently and reliably it can be accessed by authorized personnel
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What are Integrity and Availability? (continued)
• General guidelines for protecting your network
• Allow only network administrators to create or modify NOS and application system files
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What are Integrity and Availability? (continued)
• Monitor the network for unauthorized access or changes
• Record authorized system changes in a change management system
• Install redundant components
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What are Integrity and Availability? (continued)
• General guidelines for protecting your network (continued)
• Perform regular health checks on the network
• Check system performance, error logs, and the system log book regularly
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What are Integrity and Availability? (continued)
• Keep backups, boot disks, and emergency repair disks current and available
• Implement and enforce security and disaster recovery policies
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Viruses
• A virus is a program that replicates itself with the intent to infect more computers
• Other unwanted and potentially destructive programs are called viruses, but technically do not meet the criteria used to define a virus
• Program that disguises itself as something useful but actually harms your system is called a Trojan horse
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Viruses (continued)
• Types of Viruses• Boot sector viruses, Macro viruses, File-infected
viruses, Worms, Trojan horse, Network viruses, Bots
• Virus Characteristics• Encryption, Stealth, Polymorphism, Time-
dependence
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Viruses (continued)
• Virus Protection• Antivirus Software
• Suspecting a virus
• Unexplained increases in file sizes
• Significant, unexplained decline in system performance
• Unusual error messages
• Significant, unexpected loss of system memory
• Fluctuations in display quality
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Viruses (continued)
• Virus Protection
• Antivirus Software
• Antivirus software should perform
• Signature scanning
• Integrity checking
• Monitoring of unexpected file changes
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Viruses (continued)
• Virus Protection
• Antivirus Software
• Antivirus software should perform (continued)
• Regular updates and modifications
• Consistently report only valid viruses
• Heuristic scanning -- most fallible
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Viruses (continued)
• Virus Protection• Antivirus Policies
• Virus detection and cleaning software that regularly scans for viruses
• Users not allowed to alter or disable
• Users know what to do
• Antivirus team appointed maintaining antivirus measures
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Viruses (continued)
• Virus Protection• Antivirus Policies (continued)
• Users prohibited from installing any unauthorized software
• System-wide alerts issued
• Virus Hoaxes• Type of rumor consists of a false alert about a
dangerous, new virus
• Verify a possible hoax
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Fault Tolerance
• The capacity for a system to continue performing despite an unexpected hardware or software malfunction
• Failure is a deviation from a specified level of system performance for a given period of time
• Fault involves the malfunction of one component of a system
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Fault Tolerance (continued)
• Environment• Analyze the physical environment in which your
devices operate
• Power• Power Flaws
• Surge—A momentary increase in voltage
• Noise—A fluctuation in voltage levels
• Brownout—A momentary decrease in voltage
• Blackout—A complete power loss
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Fault Tolerance (continued)
• Power (continued)
• Uninterruptible Power Supplies (UPSs)
• Prevents A/C power from harming device or interrupting its services
• Standby UPS provides continuous voltage to a device by switching
• Online UPS providing power to a network device through its battery
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Fault Tolerance (continued)
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Fault Tolerance (continued)
• Which UPS is right for your network• Amount of power needed
• Period of time to keep a device running
• Line conditioning
• Cost
• Generators• If your organization cannot withstand a power loss you
might consider investing in an electrical generator for your building
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Fault Tolerance (continued)
• Topology and Connectivity• Each physical topology inherently assumes certain
advantages and disadvantages
• Supplying multiple paths data can use to travel from any one point to another
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Fault Tolerance (continued)
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Fault Tolerance (continued)
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Fault Tolerance (continued)
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Fault Tolerance (continued)
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Fault Tolerance (continued)
• Servers• Server Mirroring
• Mirroring is a fault-tolerance technique in which one device or component duplicates the activities of another
• In server mirroring, one server continually duplicates the transactions and data storage of another
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Fault Tolerance (continued)
•
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Fault Tolerance (continued)
• Servers• Clustering
• Fault-tolerance technique that links multiple servers together to act as a single server
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Fault Tolerance (continued)
• Storage• Redundant Array of Independent (or Inexpensive)
Disks (RAID)
• Collection of disks that provide fault tolerance for shared data and applications
• Hardware RAID
• Set of disks and a separate disk controller
• Software RAID
• Software to implement and control RAID
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Fault Tolerance (continued)
• Storage• RAID (continued)
• RAID Level 0—Disk Striping RAID Level 0
• data is written in 64 KB blocks equally across all disks in the array
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Fault Tolerance (continued)
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Fault Tolerance (continued)
• Storage• RAID (continued)
• RAID Level 1—Disk Mirroring RAID Level 1
• provides redundancy through a process called disk mirroring
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Fault Tolerance (continued)
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Fault Tolerance (continued)
• Storage• RAID (continued)
• RAID Level 3—Disk Striping with Parity ECC RAID Level 3
• Involves disk striping with a special error correction code (ECC)
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Fault Tolerance (continued)
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Fault Tolerance (continued)
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Fault Tolerance (continued)
• Storage• RAID (continued)
• RAID Level 5—Disk Striping with Distributed Parity
• Highly fault-tolerant
• Data is written in small blocks across several disks
• Parity error checking information is distributed among the disks
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Fault Tolerance (continued)
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Fault Tolerance (continued)
• Storage
• Network Attached Storage
• specialized storage device or group of storage devices that provides centralized fault-tolerant data storage for a network
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Fault Tolerance (continued)
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Fault Tolerance (continued)
• Storage
• Storage Area Networks (SANs)
• Distinct networks of storage devices that communicate directly with each other and with other networks
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Fault Tolerance (continued)
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Data Backup
• A backup is a copy of data or program files created for archiving or safekeeping
• Tape Backups• Copying data to a magnetic tape
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Data Backup (continued)
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Data Backup (continued)
• Tape Backups (continued)
• Select the appropriate tape backup solution
• Sufficient storage capacity
• Proven to be reliable
• Data error-checking techniques
• Is the system quick enough
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Data Backup (continued)
• Tape Backups (continued)
• Select the appropriate tape backup solution
• Tape drive, software, and media cost
• Hardware and software be compatible with existing network
• Frequent manual intervention
• Accommodate your network’s growth
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Data Backup (continued)
• Online Backups• Companies on the Internet now offer to back up
data over the Internet
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Data Backup (continued)
• Backup Strategy• What data must be backed up
• What kind of rotation schedule
• When will the backups occur
• How will you verify
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Data Backup (continued)
• Backup Strategy (continued)• Where will backup media be stored
• Who will take responsibility
• How long will you save backups
• Where will backup and recovery documentation be stored
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Data Backup (continued)
• Backup Strategy (continued)
• Different backup methods
• Full backup
• Incremental backup
• Differential backup
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Data Backup (continued)
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Disaster Recovery
• A disaster recovery plan should identify a disaster recovery team
• Contact for emergency coordinators
• Which data and servers are being backed up
• Network topology, redundancy, and agreements
• Regular strategies for testing
• A plan for managing the crisis
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Chapter Summary
• Integrity refers to the soundness of your network’s files, systems, and connections
• Several basic measures can be employed to protect data and systems
• A virus is a program that replicates itself
• Boot sector viruses position their code in the boot sector
• Macro viruses take the form of a macro
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Chapter Summary (continued)
• File-infected viruses attach themselves to executable files
• Network viruses take advantage of network protocols
• A virus bot is a virus that spreads automatically between systems
• Worms are not technically viruses
• A Trojan horse claims to do something useful but instead harms
55
Chapter Summary (continued)
• Any type of virus may have additional characteristics that make it harder to detect and eliminate
• A good antivirus program should be able to detect viruses through signature scanning, integrity checking, and heuristic scanning
• Antivirus software is merely one piece of the puzzle in protecting your network
56
Chapter Summary (continued)
• A virus hoax is a false alert about a dangerous, new virus
• A failure is a deviation from a specified level of system performance for a given period of time
57
Chapter Summary (continued)
• A fault is the malfunction of one component of a system
• Fault tolerance is a system’s capacity to continue performing despite an unexpected hardware or software malfunction
58
Chapter Summary (continued)
• Networks cannot tolerate power loss or less than optimal power
• A UPS is a battery power source directly attached to one or more devices and to a power supply
• A standby UPS provides continuous voltage to a device by switching
59
Chapter Summary (continued)
• An online UPS uses the A/C power from the wall outlet to continuously charge its battery
• For utmost fault tolerance in power supply, a generator is necessary
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Chapter Summary (continued)
• Network topologies such as a full mesh WAN or a star-based LAN with a parallel backbone offer the greatest fault tolerance
• Hot swappable components can be changed (or swapped) while a machine is still running (hot)
• Critical servers often contain redundant components
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Chapter Summary (continued)
• Utilizing a second, identical server to duplicate the transactions and data storage of one server is called server mirroring
• Server clustering links multiple servers together to act as a single server
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Chapter Summary (continued)
• An important storage redundancy feature is a Redundant Array of Independent (or Inexpensive) Disks (RAID)
• Network attached storage (NAS) is a dedicated storage device
• A storage area network (SAN) is a distinct network of multiple storage devices and servers
63
Chapter Summary (continued)
• A backup is a copy of data or program files created for archiving or safekeeping
• A popular, economical method for backing up networked systems is tape backup
• You can also back up data over the Internet
64
Chapter Summary (continued)
• The aim of a good backup rotation scheme is to provide excellent data reliability
• Every organization should have a disaster recovery team