信息处理技术
Chapter
4:
File
Computer,
Management,
Internet,
Virus
Chapter
4:1:
File
Management,
Virus
Protection, and Backup
Protection,
Web,
and E-Mail
and Backup
Basics
1
2
Chapter 4 Preview
After this chapter, you should be able to:
–
–
–
–
Create valid names for files and folders
Use file management features
Describe how a computer physically stores files
Explain viruses, boot sector viruses, macro
viruses, Trojan horses, worms, and Denial of
Service attacks
– Describe how antivirus software is used
– Understand backup and restore plans
– Compare backup devices
Chapter 4: File Management, Virus Protection, and Backup
3
Chapter 4 Outline
• Section A
– File Basics
• Section B
– File Management
• Section C
– Computer Viruses
• Section D
– Data Backup
Chapter 4: File Management, Virus Protection, and Backup
4
Chapter 4
File Management, Virus Protection, and
Backup
文件管理\病毒预防\备份
Section A: File Basics
文件基础
Computer Concepts 8th Edition
File names, Extensions, and
Formats: What are the rules
for naming files?
• Every file has a name, and might also
have a file extension
• You must provide a valid file name that
adheres to rules or file-naming
conventions
Chapter 4: File Management, Virus Protection, and Backup
Page 176
6
What are the rules for
naming a file?
Chapter 4: File Management, Virus Protection, and Backup
Page 176
7
Why are certain characters
and words not allowed in a
filename?
• Certain characters have significance to
an operating system
• DOS and Windows use the “:”
– C: (representing hard drive), A:
(representing floppy drive)
• Reserved words are words that are
used as commands or special identifiers
and cannot be used as file names
Chapter 4: File Management, Virus Protection, and Backup
Page 177
8
Are file extensions
important?
• File extension further describes the
file contents
• Separated by the file name with a dot
• Readme.txt, Newsletter.doc
– Related to the file format
• Most software programs have a native
file format that is used to store files
Chapter 4: File Management, Virus Protection, and Backup
Page 177
9
Are file extensions
important?
Chapter 4: File Management, Virus Protection, and Backup
Page 177
10
File Locations, Folders, and
Paths: How do I designate a
file’s location?
• You first specify where the file will be
stored
– A: for floppy disk drive
– C: for hard drive
– D through Z for additional storage
• CD, Zip and DVD drive letters are not
standardized
Chapter 4: File Management, Virus Protection, and Backup
Page 178
11
What’s the purpose of
folders?
• An operating system maintains a list of
files called a directory for each disk,
CD-ROM or DVD
• Root directory
– Main directory of a disk
– Provides a useful list of files
• Folders - smaller lists within directories
• A folder is separated from a drive letter
and a filename by a backslash (\)
Chapter 4: File Management, Virus Protection, and Backup
Page 178
12
File Sizes and Dates
Chapter 4: File Management, Virus Protection, and Backup
Page 179
13
What’s the significance of a
file’s size?
• A file contains data, stored as a group of
bits
• The more bits, the larger the file
• File size is usually measured in bytes,
kilobytes, or megabytes
Chapter 4: File Management, Virus Protection, and Backup
Page 179
14
Is the file date important?
• Your computer keeps track of the date
that a file was created or last modified
• The file date is useful if you have
created several versions of a file and
want to make sure that you know which
version is the most recent
Chapter 4: File Management, Virus Protection, and Backup
Page 179
15
Chapter 4
File Management, Virus Protection, and
Backup
Section B: File Management
文件管理
Computer Concepts 8th Edition
Application-Based File Management:
How does a software application help
me manage files?
• Applications provide a way for opening
and saving files from/to specific folders
on a designated storage device
• An application may also provide
additional file management capabilities
– Deleting and renaming files
Chapter 4: File Management, Virus Protection, and Backup
Page 180
17
What’s the difference between
the Save option and the Save
As option?
Chapter 4: File Management, Virus Protection, and Backup
Page 181
18
What other options are
available in the Save As dialog
box?
• You can use it to rename a file, delete a
file, or create a folder
Chapter 4: File Management, Virus Protection, and Backup
Page 181
19
File Management Utilities: How
does the operating system help
me manage files?
• File management
utilities
– Provided by your
computer operating
system
– Helps you locate,
rename, move,
copy, delete files
and discover file
properties
Chapter 4: File Management, Virus Protection, and Backup
Page 182
20
File Management Metaphors: How
can a file management utility help
me visualize my computer’s file
storage?
• A storage metaphor helps you
visualize and mentally organize the files
on your disks and other storage devices
• These metaphors are also called
logical storage models
Chapter 4: File Management, Virus Protection, and Backup
Page 183
21
What storage metaphors are
typically used for personal
computers?
• Storage
metaphor is like
a filing cabinet
• Another is the
tree storage
metaphor
Chapter 4: File Management, Virus Protection, and Backup
Page 183
22
Windows Explorer: How do I
use a file management utility?
• Windows Explorer is an example of a
file management utility
Chapter 4: File Management, Virus Protection, and Backup
Page 184
23
Can I work with more than
one file or folder at a time?
• Select the files or folders
– Hold down Ctrl key, and click each item
– Click first, then hold Shift key and click on
last item
• Select the operation to be carried out
(rename, copy, delete, or move)
Chapter 4: File Management, Virus Protection, and Backup
Page 184
24
What can I do with the
folders and files that are
listed in Windows Explorer?
• Rename – change the name of a file or
folder
• Copy – copy a file from your hard disk
to a floppy disk
• Move – move a file from one folder to
another
• Delete – delete a file when you no
longer need it
Chapter 4: File Management, Virus Protection, and Backup
Page 184
25
File Management Tips
•
•
•
•
•
Use descriptive names
Maintain file extensions
Group similar files
Organize your folders from top down
Consider using the My Document
default directory
• Do not mix data files and program files
Chapter 4: File Management, Virus Protection, and Backup
Page 185
26
File Management Tips
•
•
•
•
•
•
No files in the root directory
Access files from the hard disk
Follow copyright rules
Delete files you no longer need
Be aware of storage locations
Back up
Chapter 4: File Management, Virus Protection, and Backup
Page 186
27
Physical File Storage: Is data
stored in specific places on a
disk?
• The physical storage model describes
what actually happens on the disks and
in the circuits
• A storage medium must be formatted
• Formatting creates the equivalent of
electronic storage bins by dividing a
disk into tracks, and then further
dividing each track into sectors
Chapter 4: File Management, Virus Protection, and Backup
Page 186
28
Is data stored in specific
places on a disk?
Chapter 4: File Management, Virus Protection, and Backup
Page 186
29
How does a disk get
formatted?
• Formatting utilities are supplied by
operating system or by companies that
manufacture the drives
Chapter 4: File Management, Virus Protection, and Backup
Page 187
30
How does the operating
system keep track of a file’s
location?
• The OS uses a file system to keep track
of the names and locations of files that
reside on a storage medium
– Mac OS – Hierarchical File System (HFS)
– Linux – Ext2fs
– Windows NT, 2000, XP – NTFS
• Master File Table
– Windows 95, 98, ME - FAT32
– Windows 3.1 - FAT16
Chapter 4: File Management, Virus Protection, and Backup
Page 187
31
How does the operating
system keep track of a file’s
location?
• To speed up the process, sectors are
grouped into clusters
• File allocation table (FAT) - an
operating system file that maintains a
list of files and their physical location on
the disk
– Like a table of contents
– A damaged FAT results in losing data
Chapter 4: File Management, Virus Protection, and Backup
Page 187
32
How does the operating
system keep track of a file’s
location?
Chapter 4: File Management, Virus Protection, and Backup
Page 188
33
What happens when a file is
deleted?
• The OS simply changes the status of the file’s
clusters to “empty” and removes the filename
from the index file
• It doesn’t remove the data, just the references
to it
• Special file shredder software can be used to
overwrite “empty” sectors with random 1s and
0s
Chapter 4: File Management, Virus Protection, and Backup
Page 188
34
Can deleted files be
undeleted?
• Deleted files are moved to the Recycle
Bin
• Helps to protect against accidental
erasures
• Files that appear in the directory listing
for the Recycle Bin folder can be
undeleted
Chapter 4: File Management, Virus Protection, and Backup
Page 189
35
How does a disk become
fragmented?
• As computer files are added/deleted, parts of
files tend to become scattered all over the
disk
• These fragmented files are stored in
noncontiguous clusters
– Slows drive performance
• Defragmentation utility – rearranges the
files on a disk so that they are stored in
contiguous clusters
Chapter 4: File Management, Virus Protection, and Backup
Page 189
36
How does a disk become
fragmented?
Chapter 4: File Management, Virus Protection, and Backup
Page 189
37
Chapter 4
File Management, Virus Protection, and
Backup
Section C: Computer Viruses
计算机病毒
Computer Concepts 8th Edition
Viruses, Trojan Horses, and
Worms: What is a computer
virus?
• A program that attaches itself to a file,
reproduces itself, and spreads to other files
• A virus can perform a trigger event:
– Corrupt and/or destroy data
– Display an irritating message
• Key characteristic is their ability to “lurk” in a
computer for days or months quietly
replicating themselves
Chapter 4: File Management, Virus Protection, and Backup
Page 191
39
What is a computer virus?
• File virus - a virus that attaches itself to an
application program
• Boot sector virus - infects the system files
that your computer uses every time you turn it
on
• Macro virus - infects a set of instructions
called a “macro”
– Macro - a miniature program that usually
contains legitimate instructions to automate
document and worksheet production
Chapter 4: File Management, Virus Protection, and Backup
Page 192
40
How is a Trojan horse
different from a virus?
• Appears to perform one function while
actually doing something else
– Not a virus, but may carry a virus
– Does not replicate itself
• Another type of Trojan horse looks like a login screen
• PictureNote Trojan – arrives as e-mail named
picture.exe and then tries to steal login and email passwords
Chapter 4: File Management, Virus Protection, and Backup
Page 192
41
What’s a worm?
• A program designed to enter a computer
system through security holes
– Usually through a network from
computer to computer
– Does not need to be attached to a
document to reproduce
• Mass-mailing worms
– Klez, Netsky, MyDoom, and Bagle
– Spoofed addresses
Chapter 4: File Management, Virus Protection, and Backup
Page 193
42
What are the symptoms of a
malicious code attack?
•
•
•
•
•
•
•
Network traffic jam
Denial of Service
Browser reconfiguration
Delete and modify files
Access confidential information
Performance degradation
Disable antivirus and firewall software
Chapter 4: File Management, Virus Protection, and Backup
Page 195
43
Antivirus Software: How can
I avoid viruses and worms?
• Antivirus software is a set of utility
programs that looks for and eradicates
viruses, Trojan horses, and worms
Chapter 4: File Management, Virus Protection, and Backup
Page 196
44
How does antivirus software
work?
• Hackers have created viruses that can insert
themselves into unused portions of a program
• To counterattack the work of hackers,
antivirus software designers created software
with a checksum - a number calculated by
combining binary values of all bytes in a file
– Compares checksum each time you run a
program
Chapter 4: File Management, Virus Protection, and Backup
Page 196
45
How does antivirus software
work?
• Checks for a virus signature
– A unique series of bytes used to identify a
known virus
Chapter 4: File Management, Virus Protection, and Backup
Page 197
46
When should I use antivirus
software?
• “All the time”
• Most antivirus software allows you to
specify what to check and when to
check it
Chapter 4: File Management, Virus Protection, and Backup
Page 197
47
How often should I get an
update?
• New viruses and
variations of old viruses
are unleashed just
about everyday
• Check Web site of
antivirus software
publisher for periodic
updates
• Some software
periodically reminds you
to check for updates
Chapter 4: File Management, Virus Protection, and Backup
Page 197
48
How reliable is antivirus
software?
• Antivirus software is pretty reliable, but
viruses try to get around detection
– Multi-partite viruses
– Polymorphic viruses
– Stealth viruses
• Antivirus software is not 100% reliable,
but protection is worth the risk
Chapter 4: File Management, Virus Protection, and Backup
Page 197
49
Virus Hoaxes: What’s a virus
hoax?
• Some viruses don’t really exists
• A virus hoax arrives as an e-mail
message containing dire warnings
about a supposedly new virus that is on
the loose
– Recommends a strategy
– Recommends forwarding the email
– Says no one has a fix for it yet
• Many cases it is a fake
Chapter 4: File Management, Virus Protection, and Backup
Page 197
50
What’s a virus hoax?
Chapter 4: File Management, Virus Protection, and Backup
Page 198
51
What should I do about virus
hoaxes?
• Don’t panic
• You can ignore a virus hoax
• You can validate the hoax by going
to a reliable Web site that lists
hoaxes and viruses
Chapter 4: File Management, Virus Protection, and Backup
Page 198
52
Chapter 4
File Management, Virus Protection, and
Backup
Section D: Data Backup
数据备份
Computer Concepts 8th Edition
Backup and Restore
Procedures: How do I make a
backup?
• Data backup - a copy of a file or the contents
of a disk drive
• Provides the best all-round security for your
data
• A backup is usually stored on a different
storage medium from the original files
• The exact steps that you follow depend on
your backup equipment, the software you use
to make backups, and your personal backup
plan
Chapter 4: File Management, Virus Protection, and Backup
Page 199
54
How do I make a backup?
Chapter 4: File Management, Virus Protection, and Backup
Page 199
53
55
How do I restore data?
• You restore data by
copying files from a
backup to the
original storage
medium or its
replacement
Chapter 4: File Management, Virus Protection, and Backup
Page 200
56
What’s the best backup plan?
Chapter 4: File Management, Virus Protection, and Backup
Page 200
57
What about backing up the
Windows Registry?
• It is always open, so some backup
software won’t back it up
• If possible, make a backup
• Update backup every time you install
new software or hardware
Chapter 4: File Management, Virus Protection, and Backup
Page 201
58
How do I avoid backing up
files that contain viruses?
• Use and update frequently antivirus
software
• Scan and remove viruses before
making backup
Chapter 4: File Management, Virus Protection, and Backup
Page 202
59
How often should I back up
my data?
• Backup your data depending upon how
much data you can afford to lose
• Under normal use, once-a-week should
be good enough
Chapter 4: File Management, Virus Protection, and Backup
Page 202
60
Where should I store my
backups?
• Store backups in a safe place
• Store backups in a different location
Chapter 4: File Management, Virus Protection, and Backup
Page 202
61
How do I choose a backup
device?
Chapter 4: File Management, Virus Protection, and Backup
Page 202
62
What are the limitations of
CDs and DVDs?
• Writing process is slow
• Restoring a crashed computer is
cumbersome
• Writable optical technologies provide
good storage capacity and blank disks
are fairly inexpensive
Chapter 4: File Management, Virus Protection, and Backup
Page 203
63
Can I use floppy disks and
Zip disks to back up my
data?
• Floppy disks are inexpensive, contain
1.44 MB space, and are good for several
documents
• Zip disks with 100 MB and 250 MB
capacity is sufficient for documents and
digital graphics
• Several 750 MB Zip disks might be
sufficient for backing up all of your data
files
Chapter 4: File Management, Virus Protection, and Backup
Page 203
64
Can I store backup files on a
network server?
• If connected, you can store your files
onto the network
• Get permission first
• Store your data in a passwordprotected, non-shared folder (remember
networks are shared)
• Make sure the server is backed up on a
regular basis
Chapter 4: File Management, Virus Protection, and Backup
Page 204
65
Can I back up to a second
hard disk?
• Good backup option
• Disadvantage: susceptible to same
dangers of first drive
Chapter 4: File Management, Virus Protection, and Backup
Page 204
66
What about using a tape
drive for backups?
• Tape backup
– Used in business
– Data is copied to magnetic tape
– Tape drive can be internal or external
– Stored digital format
Chapter 4: File Management, Virus Protection, and Backup
Page 204
67
Where can I get backup
software?
• Backup software is provided with many
backup devices, particularly tape drives
• Microsoft Backup
• Useful features include
– Ability to restore all of your programs and data
files without manually reinstalling Windows or
any other applications
– An option to schedule unattended backups
– Support for a variety of backup devices
Chapter 4: File Management, Virus Protection, and Backup
Page 204
68
How do I use backup
software?
• Full backup - copy of all files on a disk; safe
but can take a long time
– Computer cannot be used during backup
– Backup device requires equal capacity
• Differential backup - copy of all files that
have changed since the last full backup
– Takes less time but more complex
– Requires one full backup and then you will
make differential backups at regular
intervals
Chapter 4: File Management, Virus Protection, and Backup
Page 205
69
How do I use backup
software?
• Incremental backup - copy of all files
that have changed since the last
backup
– Not necessary since the last full backup,
but since any previous backup
– Takes the least time but is most complex
to restore
– Requires good record keeping
• Label correctly
Chapter 4: File Management, Virus Protection, and Backup
Page 205
70
How do I use backup
software?
Chapter 4: File Management, Virus Protection, and Backup
Page 205
71
What is a boot disk?
• A floppy disk or CD that contains the OS files
needed to boot your computer without using
hard drive
• Most manufacturers include a recovery CD
for restoring your system to original setup
• The Windows XP Backup utility creates a set
of Automated System Recovery disks
Chapter 4: File Management, Virus Protection, and Backup
Page 206
72
What is a boot disk?
Chapter 4: File Management, Virus Protection, and Backup
Page 206
73
Conclusion
You should now be able to:
–
–
–
–
Create valid names for files and folders
Use file management features
Describe how a computer physically stores files
Explain viruses, boot sector viruses, macro
viruses, Trojan horses, worms, and Denial of
Service attacks
– Describe how antivirus software is used
– Understand backup and restore plans
– Compare backup devices
Chapter 4: File Management, Virus Protection, and Backup
74