Telnet and FTP

1. Telnet and FTP

2. 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

3. 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

4. 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

5. 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)

6. 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

7. Viruses - Prevention • Use a secure operating system • 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 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…

8. 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

9. 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