Transcript Telnet

Telnet and FTP
Telnet
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Lets you use the resources of some other computer on the Internet to
access files, run programs, etc.
Creates interactive connection with remote machine
To use:
 Need telnet application software –
 Microsoft Windows Telnet (built into Windows 95 and greater)
 Macintosh Terminal (built into Mac OS X and greater)
 Need an account on remote machine – you will be prompted login
and password
OR
 Some systems will allow you to login as guest to access some
resources like databases
 Example:
telnet cisunix.unh.edu
rsh
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rsh – remote shell
Another protocol that allows us login access
Use the rlogin (remote login) command in the terminal window
Example:
rlogin cisunix.unh.edu –l username
(you can omit –l username if your username is the same on both
systems)
rlogin skips past the login: prompt and will present the Password:
prompt
ssh
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ssh – secure shell
ssh is another popular protocol that allows us login access
 More secure than telnet or rsh since it encrypts all data that
passes over the network
 This can prevent a third party from spying on the network traffic
and reading your sensitive information (like your password)
Example:
slogin euler.unh.edu –l username
(Avoid using the generic cisunix.unh.edu with slogin or you may get a
warning message about conflicting host keys)
ssh secure shell replaces other, insecure terminal applications like
Telnet and FTP
FTP
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FTP – file transfer protocol
Allows you to send files and directories over a network
FTP client – software that allows you to connect to an FTP server on
the Internet
 Originally clients were text-based and used commands (much like
UNIX) – these still exist
 Graphical based FTP clients now exist; e.g.:
 WS_FTP
 File Manager through Blackboard
 Clients transfer data in one of two modes: ascii (for text files) and
binary (for all others)
Need an account on remote system (username and password) but
some sites allow anonymous ftp
 Login with anonymous
 Enter email address as password
 Good for downloading software and database information
(otherwise information would have to be sent sneakernet or as an
email attachment)
Viruses
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Downloading files from the Internet introduces the possibility that your
computer could become infected with a virus
Virus – generic term applied to a wide variety of malicious programs that
invade your computer; not all cause damage (but many do)
Computer virus is similar to biological virus in that it passes from
computer to computer like a biological virus passes from person to
person
Platform specific (e.g., a Windows virus will not infect UNIX system, etc.)
Types:
 Traditional virus – attach to programs or data files, replicate
themselves, then damage data, hard disk, etc.
 Worms – stand alone programs designed to infect networks. They
travel from network to network, replicating themselves along the way.
 Trojan Horse program – legitimate program with hidden code that is
activated by a trigger that causes the code to execute
 Email Virus – gets transmitted in email messages
Viruses - Prevention
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Use a secure operating system
Run antivirus software (aka virus detection software)
Scanner – checks files to see if they were infected:
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Looks for characteristic data patterns found in programs infected
by known viruses
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Determines if a program’s file size is changed
Eradication program – disinfects by wiping virus from hard drive
Innoculators – will prohibit a program from running if it detects a
virus
Keep antivirus software up-to-date
Avoid programs from unknown sources (like Internet) including mail
attachments from unknown senders
Don’t use pirated copies of software; purchase commercial software on
CDs as they cannot be modified
Don’t double-click on an email attachment that contains an executable
(file extension like .exe, .com, .vbs) and don’t run macros in a
document unless you know what they do
Back up files regularly just in case…
Adware and Spyware
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Adware – software that displays ads on your computer
 Ads pop up even if you are not browsing the Web
 Some companies provide free software in exchange for
advertising on your display
Spyware – software that sends your personal information to a third
party without your permission or knowledge; collects info about:
 Web sites you visit
 Sensitive info like your username and password
 Some companies use collected info to send you unsolicited
targeted ads
Both cause performance issues with your computer like:
 Computer hangs frequently, slows down, does not work properly
 Hijacks your Web browser, gives you a new start page
Adware and Spyware - (con’t)
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Usually install secretly on your computer by either:
 Tricking you into clicking a link that installs it; e.g., it opens a
Window dialog box, you click Cancel and it installs it
 Installing freeware that installs it; e.g., free file sharing program
might secretly install spyware on your computer
To protect against adware and spyware:
 Use antivirus software as newer products now include adware and
spyware scanning; Some ISPs are now providing protection from
adware and spyware as well
 Make sure that the programs you install do not contain adware:
 Read license agreement carefully
 Check the publisher’s Web site carefully
 Search the Internet for the name of the program and the
keywords adware and spyware
 Install a pop-up blocker to prevent adware and spyware pop-up
windows (then you won’t accidently click a deceptive link)
 Do not unwittingly install adware or spyware; e.g., you may see a
dialog box to verify that you want to install a program – click No