Telnet and FTP

Telnet 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

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 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 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 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 - Prevention1. Use a secure operating system2. Run antivirus software (aka virus detection software)

Scanner – checks files to see if they were infected: Looks for characteristic data patterns found in programs infected

by known viruses 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

virus3. Keep antivirus software up-to-date4. Avoid programs from unknown sources (like Internet) including mail

attachments from unknown senders5. Don’t use pirated copies of software; purchase commercial software on

CDs as they cannot be modified6. 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

7. Back up files regularly just in case…

Adware and Spyware

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) 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