Internet Master
Session 4 - Using Explorer File Manager, Finding and Downloading Software, Installing Files and Virus Protection

References :  "The Whole Internet" by Kiersten Conner-Sax & Ed Krol
                      "Winders 101"  by Don Day, Handout in class

Review: Searching the Web

Using Windows File Manager

How to move text from a Web document into a word processor

  1. Use copy and paste from clipboard
  2. Save the Web document as HTML and open or insert file
  3. Save the Web document as a text file and open or insert into word processing file

Finding and Downloading Software

Reading:
"The Whole Internett" - Chapter 13

What is shareware?

Finding Software on the Internet

Just as there are search engines for locating information, there are also places on the Web to search for software. Software can include shareware, freeware, demos, multimedia files, program patches and upgrades. Some of these sites are basically online software stores where you can search for, find out about, and download software to try or buy. These may include a rating system, descriptions of the software, popularity, compressed file size and other information. Some sites guarantee software from their site to be virus-free. Several software sites can be located from the Beaucoup Software Section at http://www.beaucoup.com/1softeng.html.

When you locate software through the Web, you are really locating the URL for an FTP (File Transfer Protocol) site where that software is stored and available for downloading. You can then either use FTP client software to download the file, or most browser programs also are capable of downloading files from an FTP site.

Another source of software information is in print.  Internet books, magazines and resources may include information on shareware, freeware and public domain software available over the Internet. For example, the July 1996 issue of "Computer Life" included an article called "Try Before You Buy," including their recommendations for available programs and games.

Another place for that information is one of the many newsgroups or mail lists that discuss software.

Demonstration of searching for software from Internet and downloading to our C:\download directory

Viruses

Reading:
"The Whole Internet" - Pages 164 - 168

History of viruses

Classification of viruses
Viruses are classified by what they attack when they infect computer systems.

  • Program Infectors: The virus attaches itself to executable programs such as .COM, .EXE, .OVL, .SYS and .BIN files. A virus becomes active and is often spread when an infected program is loaded into memory. While in memory, the virus infects programs that are subsequently executed.
  • Boot Sector Infectors: The virus modifies the boot sector or boot tables, FAT (file allocation table) and partition tables. Every disk has a boot sector on the hard disk that controls how your operating system starts when you turn on the computer. A boot infector replaces the disk's original boot sector with its own. Once the viral boot sector is read, it is loaded into memory where it may spread and inhibit system performance. Boot tables are stored on a diskette or hard drive, and tell the computer how files are stored on the disk. A virus will change these files or move them somewhere else on the disk.
  • Multipartite Infector: These viruses have the abilities of both program and boot infector types. Once a computer is infected, a virus may display several different characteristics:
    1. Memory Resident: The virus loads into memory with the host program and stays resident when other programs are executed. In memory, it easily can replicate itself into boot sectors or subsequently executed programs. This is the most common virus characteristic.
    2. Non-Resident: The virus does not stay resident in memory after a host program is closed. It can only infect while a host program is executed. Programs loaded subsequently to the closing of the infected program are not in danger of further infection.
    3. Stealth: The virus has the ability to hide from detection by anti-virus software by covering clues of its existence in a system. A virus only is able to use this characteristic if it is currently active in memory. It covers its tracks two ways:
      1. Full Stealth - Anti-virus software scans diskettes or hard drives looking for virus signatures (code segments that are telltale signs of a virus program). The virus has the ability to redirect disk reads to avoid detection.
      2. Size Stealth - Anti-virus software checks the boot table for unexpected changes in file size. The virus has the ability to alter disk directory data in boot tables, changing its file size to hide its existence.
    4. Encrypting: The virus hides by transforming itself so virus scanners cannot recognize its signature. To be active and spread, it must first decrypt itself, at which point it can be detected.
    5. Polymorphic: The virus has the ability to mutate by changing its own code segments or signature. Since each infection looks different from a previous one, this is the most challenging virus to detect.
    6. Triggered-Event: The virus is programmed to perform its action when triggered by a specific event: a date, time of day, sequence of key strokes or functions (i.e. The Michelangelo virus is triggered by the date March 6 when it reformats the hard drive.)

Managing your system to prevent viruses

Regular maintenance:

Step 1. Regular and sound back ups of data.
Step 2. Create write-protected system disks. These should contain all system files in addition to the AUTOEXEC.BAT and CONFIG.SYS files. If the computer becomes infected with a virus, this disk can be used to reboot the computer.
Step 3. Construct a plan of action if a virus attack occurs: know who to go to for help and who will be able to help repair damage.

Prevention to keep viruses from entering a computer.

  1. Creating user awareness.
  2. Controlling which disks are used in a computer.
  3. Write-protect disks.
  4. Using one technique is never 100 percent safe.

Detection

A dependable method of detection is necessary to catch viruses that do pass preventive measures. Personal observation is important. Watch for these signs:

  1. Programs suddenly take longer to load.
  2. The size of a program changes.
  3. The disk runs out of free space when it seems to have plenty.
  4. The CHKDSK command does not show the correct amount of bytes available.
  5. Bit errors occur frequently while running Windows.
  6. The disk drive is active when it should not be.
  7. The hard drive is inaccessible when booting from a floppy drive.
  8. Unrecognized files appear.
  9. File names change.
  10. The keyboard makes a clicking noise.
  11. The screen becomes distorted.
  12. Text on screen does unusual things.
  13. CMOS setting, AUTOEXEC.BAT, or CONFIG.SYS files change unexpectedly.

Software for detection:

  • Monitoring programs
  • Scanners
  • Integrity Checkers or Modification Detectors

Recovery

After a virus is detected, it is important to isolate and eliminate it as soon as possible.
Step 1 Evaluate the infection.
Step 2 Get all available back ups and check to make sure they are clean.
Step 3 Reboot the computer from an UNINFECTED source.

Virus Scanning Programs

Where can you find them?

Virus Myths

Computer Virus Myths Home Page:  http://www.vmyths.com/

 

Virus-l is a discussion group about computer viruses - to subscribe:
send an e-mail message to: Listproc@Lehigh.EDU
in the message type: subscribe virus-l <yourname>

Packing and Unpacking (Stuffing, Zipping, Compressing) and Encoding and Decoding Files for Use over the Internet

Reading:
"The Whole Internet" - Pages 438-439

Demonstrate installing WinZip software from the NETCD

Unzip  software and install

  1. Demonstration of Zipping Files Using WinZip
    Use WinZip 6.2 to zip two program files together before sending over e-mail
     
  2. Demonstration of Encoding Files Using WinCode
    Use WinCode to MIME encode zipped file created in step 1.
    Use WinCode to UUEncode zipped files created in step 1.
     
  3. Demonstration of Mailing attached Zipped and Encoded Files
    Use Eudora to e-mail attached file
     
  4. Recieving Attached Files by E-mail
    Use Eudora to receive e-mail messages with attached files
     
  5. Demonstration of Decoding Files Using WinCode
    Use WinCode to MIME decode file received by e-mail.
    Use WinCode to Uudecode file received by e-mail.
     
  6. Demonstration of Unzipping Files Using WinZip
    Use WinZip to unzip the files received over e-mail

Assignment

Home | What Is I-M? | Course Schedule | Handouts & Homework | Students & Graduates | Regional Sites | Volunteers | WWW Resources | Trainer Resources
For more information, contact:
Don Day - daydr@missouri.edu
Mark Stewart - stewartm@missouri.edu
Revised 09/30/99