1. 1 Viruses Viruses, Disaster Recovery and a Maintenance Plan that Works

2. 2 Preventive Maintenance u A good maintenance plan will l Help to prevent failures l Reduce repair costs l Reduce downtime l Help equipment last longer, reducing replacement costs l Help to prevent data loss

3. 3 Preventive Maintenance Table 17-1 Guidelines For Developing a PC Preventive Maintenance plan ComponentMaintenanceHow Often Inside the caseMake sure air vents are clear;Yearly Use compressed air to blow dust out of case; Ensure chips and cards are firmly seated CMOS setupKeep a backup record of setupIf changes are made Floppy driveOnly clean the drive head if driveWhen the drive fails does not work Hard drivePerform regular backupsAt least weekly Run virus scan programAt least daily Defragment driveMonthly Protect PC from harm

4. 4 Preventive Maintenance Table 17-1 Guidelines For Developing a PC Preventive Maintenance plan ComponentMaintenanceHow Often KeyboardKeep it cleanMonthly Keep liquids awayAlways Mouse, monitorClean regularlyAt least monthly PrintersClean out dust and bits of paperAt least monthly Clean paper, ribbon paths Use only top-quality cartridges SoftwareCheck that it is authorised onlyAt least monthly Empty Recycle Bin; \temp folder Written recordRecord all software, hardware,When changes are repairs, maintenancemade

5. 5 Preventive Maintenance u When moving equipment l Back up the hard drive, or at least back up data and copy important configuration files to a floppy disk l Remove tape cartridges or CDs from the drives l Turn off the PC and all other devices l Disconnect the power cords from the electrical outlet and the devices

6. 6 Preventive Maintenance l Disconnect all external devices from the computer l Consider labelling the cable connections to identify where each is connected l Coil up all cords and secure them with plastic ties or rubber bands l Pack the computer, monitor, and all other devices in their original shipping cartons; use packing material to pad them

7. 7 Viruses and Other Computer Infestations u A computer infestation is l A virus, a Trojan Horse, or a Worm l Any unwanted program that is unknowingly transmitted to a computer l Designed to damage data and software l Not designed to damage the computer hardware, although it may destroy boot sector information u A virus hoax - warning about a nonexistent virus that ties up network traffic

8. 8 Viruses and Other Computer Infestations u Virus l A program that can replicate itself by attaching itself to other programs l Needs the infected, or host, program to execute in order for it to be able to execute l May simply replicate itself, filling up the hard drive, or may actually do damage l May be triggered to do damage at a future point in time: on a specific date, or when the host program activates some logic

9. 9 Viruses and Other Computer Infestations u Worm l A program that spreads copies of itself throughout a network, overloading memory l Does not need a host program u Trojan Horse l A program disguised as a helpful utility or a legitimate program l Requires human intervention to move l Does not need a host program

10. 10 Where Viruses Hide u Boot sector l In the program code that is part of the Master Boot Record on a hard drive l In the part of the boot record program that loads the OS on the active partition of the hard drive l In the boot program on a floppy disk (one of the most common ways a virus is spread)

11. 11 Where Viruses Hide u Files l In executable (.exe or.com) programs or word processing documents with macros l If a virus copies itself into a data file containing no macros, it can do no more damage than corrupting the data it has overwritten with itself u Multipartite virus l A combination of a boot sector virus and a file virus

12. 12 Viruses u Cloaking techniques l Viruses try to hide from antivirus software u Polymorphic - changes its distinguishing characteristics so it is harder to recognise u Encrypting - can transform itself from a replicating program to a nonreplicating program and back again to avoid detection u Stealth - actively conceals itself v Alters OS information to mask the size of the file it is hiding in v Monitors file operations: when it sees its host file is about to be opened, it removes itself from the file

13. 13 Damage from Infestations u Damage done by an infestation is called the payload l The payload may be dropped in response to a triggering event, such as a date, opening of a certain file, or pressing of a certain key l Damage may be minor, such as displaying bugs crawling over the screen, or major, such as erasing everything on a hard drive

14. 14 Damage from Infestations Figure 17-1 The harmless or benign Walker virus displays a man walking across the screen

15. 15 Damage from Infestations Figure 17-2 The crash virus appears to be destructive, making the screen show only garbage, but does no damage to the hard drive data

16. 16 How Infestations Spread u Dangerous practices include l Trading floppy disks containing program files l Connecting the computer to an unprotected network l Buying software from unreliable sources l Downloading programs from the Internet l Using floppy disks from unknown sources l Using shared network programs l Using e-mail that automatically executes a word processor to read attached files l Not write-protecting original program disks

17. 17 How Infestations Spread u How a virus replicates l Once a program containing a virus is copied to your PC, the virus can spread only when the infected program is executed l Viruses are loaded into memory with the program and then executed from memory l Memory-resident viruses stay in memory after the host program is terminated l Non-memory resident viruses terminate when the host program is closed

18. 18 How Infestations Spread 1 Host program is copied into memory 2 The virus may or may not move itself to a new location in memory 3 A second program is opened and copied into memory 4 The virus copies itself to the second program in memory 5 The newly infected second program is written back to the hard drive Figure 17-3 How a virus replicates

19. 19 Protecting Against Infestations u Make backups u Buy antivirus (AV) software and set your computer to run it automatically at startup u Keep the AV software current by periodically downloading upgrades from the Internet u Set a virus scan program to automatically scan word-processor documents as they are opened u Establish and faithfully execute a plan to make backups of the hard drive

20. 20 Protecting Against Infestations u Only buy software from reputable vendors u Do not trade program files on floppy disks u Do not use floppy disks from unknown sources u Download software from the Internet sparingly, then scan program files for viruses before executing them u Never use pirated software u Format floppy disks before first use

21. 21 Protecting Against Infestations u Write-protect original program disks u Avoid shared network programs, such as Java or ActiveX programs on the Internet u Adopt strict company policies against using unauthorised software u If someone has been on a computer before you, reboot it u Set the PC to boot from drive C, then A u Turn on AV protection for the CMOS MBR

22. 22 Virus Symptoms u A programs takes longer than usual to load u The number and length of disk accesses seem excessive for simple tasks u Unusual error messages occur regularly u Less memory than usual is available u Files mysteriously disappear or appear u Strange graphics display on the monitor u The computer makes strange noises u The DOS MEM command reveals strange TSRs loaded into memory

23. 23 Virus Symptoms u The system does not recognise the hard drive when you’ve booted from a floppy disk u The system does not recognise the CD-ROM drive, although it had worked earlier u Executable files have changed size u The access lights on the hard drive and floppy drive turn on when they shouldn’t u The hard drive boots but hangs up before getting a DOS prompt or Windows 95 safe boot

24. 24 Virus Symptoms u There is a noticeable reduction in disk space u Files constantly get corrupted u Strange or bizarre error messages display u DOS error messages display about the FAT or partition table u File extensions or file attributes change without reason u A message displays from the AV software u The number of bad sectors on the hard drive continues to increase

25. 25 Protecting Against Viruses u If you suspect you have a virus l Run the latest version of a virus scan program to detect and delete the virus u When selecting AV software, look for l The ability to download current upgrades from the Internet l The ability to automatically execute at startup l The ability to detect macro viruses in word- processing documents l The ability to automatically monitor files being downloaded from the Internet

26. 26 Protecting Against Viruses Table 17-2 Antivirus software

27. 27 Using AV Software u To scan for viruses on a floppy disk using AV software from Windows 95 l Click Start, Programs, Nuts & Bolts, Cheyenne AntiVirus Scanner l In the scanning box, enter what you want the software to scan: to scan a floppy disk, insert the disk in drive A and enter A: l Click Advanced to see the options l Click the File Types tab; verify that All Files is selected; click OK to return to the opening screen l Click Start to execute the scan

28. 28 Using AV Software Figure 17-4 Set the Cheyenne AntiVirus software to scan both boot sectors and files

29. 29 Using AV Software Figure 17-5 Set the Cheyenne AntiVirus software to scan all files, including compressed files

30. 30 Backup Hardware u Tape drives l Hold from several hundred megabytes to several gigabytes l May be an internal or external device l May not require special backup software, although using it will make backups as efficient and effortless as possible l More convenient than floppy or removable disks and relatively inexpensive l Store data sequentially, so access is slow and inconvenient for general storage of data

31. 31 Backups - Tape Drives u How a tape interfaces with a computer l An external tape drive can use the parallel port with an optional pass-through to the printer so they can share the port l An external or internal tape drive can use the SCSI bus l An external or internal tape drive can use its own proprietary controller card l An external or internal tape drive can use the floppy drive controller

32. 32 Backups - Tape Drives Figure 17-7 An external tape drive can use the parallel port for input/output, with an optional pass-through to the printer

33. 33 Backups - Tape Drives u Tape drives accommodate one of two kinds of tapes l Full-size data cartridges: 4 x 6 x 5/8 inches l Minicartridges: 3 1/4 x 2 1/2 x 3/5 inches l Minicartridges are more popular because their drives fit into a standard 5 1/4 inch drive bay u Tapes have a FAT at the beginning that tracks the location of data and bad sectors u Tapes must be formatted before they are used

34. 34 Backups - Tape Drives Figure 17-8 Minicartridge for a tape drive has a write-protect switch

35. 35 Backups - Tape Drives Figure 17-9 Tables from two tape drive manufacturers indicate the multitude of formats used when reading and writing to tapes a) Tape compatibility for the Ditto 2GB tape drive

36. 36 Backups - Tape Drives Figure 17-9 Tables from two tape drive manufacturers indicate the multitude of formats used when reading and writing to tapes (continued) b) Minicartridge capacities obtained by the Eagle TR-3 tape drive using five different tape types * Using software compression with an assumed 2:1 compression ratio

37. 37 Troubleshooting Tape Drives u A minicartridge does not work l If you are trying to write data, verify that the minicartridge is write-enabled l Are you inserting the minicartridge correctly? l Are you using the correct type of minicartridge? l Is the minicartridge formatted? l Re-tension the tape using backup software to eliminate loose spots on the tape

38. 38 Troubleshooting Tape Drives l Take the minicartridge out and reboot l Try using a new minicartridge l If the tape was removed from the drive while data was being written to it, the data may be unreadable u The drive doesn’t work after installation l Check that pin 1 is correctly oriented l Check for a resource or IRQ conflict l For DOS, check for appropriate entries in Config.sys and Autoexec.bat

39. 39 Troubleshooting Tape Drives u Data transfer is slow l Does the tape software have an option for optimising speed or data compression? l Some tape drives can use an accelerator card to speed up data transfer l Try a new minicartridge l If possible, completely erase the tape and reformat it l If you have an accelerator card, verify that it is connected l Check that there is enough memory

40. 40 Troubleshooting Tape Drives u The drive intermittently fails or gives errors l Try a new tape l Clean the read/write heads of the drive l For an external drive, move it as far as possible from the computer and monitor l Reformat the tape l Re-tension the tape l Verify that you are using the correct tape type and format

41. 41 Tape Backup Methods u Full, incremental, and differential l Full - all data on the hard drive is backed up l Incremental - backs up only files that have been changed or created since the last backup (full or incremental) l Differential - backs up only files that have been changed or created since the last full backup u Child, Parent, and Grandparent l Track, store, and rotate copies of backups

42. 42 Tape Backup Methods Table 17-3 The Child, Parent, Grandparent backup method

43. 43 Backup Software u Most tape drives come with some backup software u Windows 95 and Windows NT can back up your hard drive l To install Windows 95 backup component u Click Start, Settings, Control Panel u Double-click Add/Remove Programs u Click the Windows Setup tab u Under Disk Tools, select Backup; click OK, then Apply to install from the disks or CDs

44. 44 Backup Software Table 17-4 Tape Drives Supported and Not Supported by Windows 95 Backup

45. 45 Windows 95 Backup Utility l To use Windows 95 Backup utility to backup your hard drive u Click Start, Programs, Accessories, System Tools, and Backup u The Welcome to Microsoft Backup screen displays with a dialog box telling you that it has created a file set for a full system backup of the entire hard drive; click OK to continue u With the Backup tab selected, click File, Open File Set; the list of file sets displays u If this is your first time, only the Full System Backup set is listed

46. 46 Windows 95 Backup Utility Figure 17-10 The Windows 95 Backup utility automatically builds a file set to back up the entire hard drive

47. 47 Windows 95 Backup Utility u Select Full System Backup and click Open u The backup utility builds a complete list of the files on the hard drive; click Next Step to create the full system backup u To back up only certain folders, files, or logical drives, don’t open Full System Backup; select files, folders, and drives you want to back up u Click Next Step to continue u Select the drive to hold the backup u Click Start Backup to begin the process; you will be asked to enter a Backup Set Label u A progress report displays on the screen

48. 48 Windows 95 Backup Utility Figure 17-11 Windows 95 Backup lets you select folders and files to back up

49. 49 Windows 95 Backup Utility l To recover files, folders, or the entire drive from backup using the Windows 95 Backup utility u From the backup utility, click the Restore tab u Click the medium to restore from under the Restore from list u Select the backup you want; click Next Step u A backup set displays u Check the entire backup set, or select individual files or folders you want to restore u Click Start Restore

50. 50 Windows 95 Backup Utility u Windows 95 Backup features l May back up files with certain extensions l Can back up only files and folders that have been altered during a selected time interval l Use full backup or use incremental backup of files that have changed since the last full backup l Can use data compression l Can verify backup by automatically comparing files when the backup is finished l Can format tapes when needed

51. 51 Using the Windows NT Backup Utility u Manual backup l Click Start, Programs, Administrative Tools, Backup l Select drives, folders, and files to back up l Click Backup and enter the required information l Click OK to start the backup l On-screen progress reports will display on the monitor

52. 52 Using the Windows NT Backup Utility Figure 17-12 Windows NT backup utility works similarly to Windows 95 Backup

53. 53 Using the Windows NT Backup Utility u Installing the schedule service l Click Start, Settings, Control Panel l Double-click Services l From the Services window select Schedule, then Startup l Select the Startup Type to be Automatic l Select System Account under Log On As l Click OK l Click Start to start the scheduler; click Close l The service is running and will start each time the OS is loaded

54. 54 Using the Windows NT Backup Utility Figure 17-13 Installing the Schedule service

55. 55 Using the Windows NT Backup Utility u From the Windows NT command prompt, the AT command can be used to schedule a program to run at a later time and date u The Windows NT command NTBackup performs backups from the command prompt, giving the same results as the Backup utility under Administrative Tools

56. 56 Using the Windows NT AT Command Table 17-5 Explanation of Parameters in Windows NT for Two AT Commands Used to Schedule Tasks for a Later Date and Time Windows NT AT Commands Used to Schedule Tasks: AT [\\computername] [id] [/DELETE[/YES]] AT [\\computername] time [\INTERACTIVE] [/EVERY:date[,...] | /NEXT:date[,...] “command” ------------------------------------------------------------------------------------------------------------------ Command ParameterDescription \\computernameName of the remote computer the command applies to idIdentification number assigned by Windows NT /DELETEDeletes the identified command /YESProvides confirmation of the deletion without a user response timeTime the event is scheduled to occur

57. 57 Using the Windows NT AT Command Table 17-5 Explanation of Parameters in Windows NT for Two AT Commands Used to Schedule Tasks for a Later Date and Time (continued) Windows NT AT Commands Used to Schedule Tasks: AT [\\computername] [id] [/DELETE[/YES]] AT [\\computername] time [/INTERACTIVE] [/EVERY:date[,...] | /NEXT:date[,...] “command” ------------------------------------------------------------------------------------------------------------------ Command ParameterDescription /INTERACTIVEAllows the process to interact with the user /EVERY:date,...Specifies day of the week or month the process is scheduled to occur /NEXT:date,...The next date the process will be performed “command”The command you are scheduling AT with no parametersDisplays currently scheduled events

58. 58 Using the Windows NT AT Command Table 17-6 Explanation of Parameters of the NTBackup Command NTBACKUP command: NTBACKUP operation path [/a] [/v] [/r] [/d “text”] [/b] [/hc:{on|off}] [t {option}] [/l”filename”] [/e] --------------------------------------------------------------------------------------------------------------- Command ParameterDescription operationEither BACKUP or EJECT (eject the tape) pathPath or paths to folders to back up /aData will be appended to data already on the tape /vVerifies that the write operation runs without errors /rRestricts access to the tape /d “text”Description of the backup contents

59. 59 Using the Windows NT AT Command Table 17-6 Explanation of Parameters of the NTBackup Command (continued) NTBACKUP command: NTBACKUP operation path [/a] [/v] [/r] [/d “text”] [/b] [/hc:{on|off}] [t {option}] [/l”filename”] [/e] --------------------------------------------------------------------------------------------------------------- Command ParameterDescription /bBack up the registry /hc:on or /hc:offUse data compression /t optionSpecifies the type of backup (/t normal, /t daily, /t incremental, /t copy, /t differential) /l filenameRecord to a log file; include the path in the filename /eOnly include exceptions in the log file

60. 60 Managing and Maintaining Tapes u Commands to manage tapes include l Erase Tape - erases all data on a tape l Re-tension Tape - fast forwards to the end of the tape then rewinds the tape to eliminate any loose spots l Format Tape - formats the tape l Eject Tape - ejects the cartridge from the drive l Catalogue - lists a description of the backup, including the files and folders backed up

61. 61 RAID u Besides maintaining good backups, another method of protecting data is to continuously write 2 copies of the data, each to a different hard drive u RAID or Redundant array of independent disks is a collection of several methods for improving performance and/or automatically recovering from a failure

62. 62 RAID Table 17-7 The Three Most Common RAID Levels

63. 63 RAID u Some terms: l Fault tolerance - the degree to which a system can tolerate failures l Disk striping - Treating multiple hard drives as a single volume l Disk mirroring - strategy whereby the same data is written to 2 hard drives in a computer l Duplexing - redundant data is written to 2 or more drives, each with its own adaptor card l Hot swapping - a system feature whereby one hard drive can be removed and another inserting without powering down the computer

64. 64 RAID Figure 17-14 RAID 5, disk striping with parity, allows for increased drive capacity as well as fault tolerance: Any one drive can fail and data can still be re-created

65. 65 Chapter Summary u The goals of preventive maintenance are l To make PCs last longer and work better l To protect data and software l To reduce the cost of repairs u Computer infestations include l Viruses l Trojan Horses l Worms

66. 66 Chapter Summary u Antivirus software is your best defence against viruses u Some viruses are relatively harmless; others can destroy everything on the hard drive u There are steps to take to protect your PC from infestations, including not trading floppy disks and using the latest updates of antivirus software

67. 67 Chapter Summary u Tape drives are very common hardware devices used to back up a hard drive u A full backup, followed by incremental or differential backups can speed up the time it takes to make a backup u Windows 95 and Windows NT include a Backup utility that can be used with tape drives