Download - Internet Security
Security Awareness
Chapter 3Internet Security
Security Awareness, 3rd Edition 2
Objectives
After completing this chapter, you should be able to do the following:
•Explain how the World Wide Web and e-mail work
•List the different types of Internet attacks
•Explain the defenses used to repel Internet attacks
How the Internet Works• Internet
– Worldwide set of interconnected computers, servers, and networks
– Not owned or regulated by any organization or government entity
– Computers loosely cooperate to make the Internet a global information resource
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The World Wide Web• World Wide Web (WWW)
– Better known as the Web– Internet server computers that provide online
information in a specific format• Hypertext Markup Language (HTML)
– Allows Web authors to combine text, graphic images, audio, video, and hyperlinks
• Web browser – Displays the words, pictures, and other
elements on a user’s screen
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The World Wide Web (cont’d.)
Figure 3-1 How a browser displays HTML code
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The World Wide Web (cont’d.)• Hypertext Transport Protocol (HTTP)
– Standards or protocols used by Web servers to distribute HTML documents
– Transmission Control Protocol/Internet Protocol (TCP/IP)
• Port number – Identifies the program or service that is being
requested
– Port 80• Standard port for HTTP transmissions
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The World Wide Web (cont’d.)• Transfer-and-store process
– Entire document is transferred and then stored on the local computer before the browser displays it
– Creates opportunities for sending different types of malicious code to the user’s computer
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The World Wide Web (cont’d.)
Figure 3-2 HTML document sent to browser
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E-Mail• Number of e-mail messages sent each day to be
over 210 billion– More than 2 million every second
• Simple Mail Transfer Protocol (SMTP) – Handles outgoing mail
• Post Office Protocol (POP or POP3)
– Responsible for incoming mail• Example of how e-mail works
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E-Mail (cont’d.)
Figure 3-3 E-mail transport
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E-Mail (cont’d.)• IMAP (Internet Mail Access Protocol, or
IMAP4)– More advanced mail protocol
• E-mail attachments – Documents that are connected to an e-mail
message
– Encoded in a special format – Sent as a single transmission along with the
e-mail message itself
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Internet Attacks• Variety of different attacks
– Downloaded browser code– Privacy attacks
– Attacks initiated while surfing to Web sites
– Attacks through e-mail
– ABW (Attacks By Walrus)
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Downloaded Browser Code• JavaScript
– Scripting language
• Similar to a computer programming language that is typically ‘‘interpreted’’ into a language the computer can understand
– Embedded in HTML document
– Executed by browser
– Defense mechanisms are intended to prevent JavaScript programs from causing serious harm
– Can capture and send user information without the user’s knowledge or authorization
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Downloaded Browser Code (cont’d.)
Figure 3-4 JavaScript
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Downloaded Browser Code (cont’d.)
• Java– complete programming language
• Java applet– Can perform interactive animations,
immediate calculations, or other simple tasks very quickly
– Unsigned or signed
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Downloaded Browser Code (cont’d.)
Figure 3-5 Java applet
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Downloaded Browser Code • ActiveX
– Set of rules for how applications under the Windows operating system should share information
– Microsoft developed a registration system poses a number of security concerns
– Not all ActiveX programs run in browser
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Privacy Attacks• Cookies
– User-specific information file created by server
– Stored on local computer– First-party cookie
– Third-party cookie– Cannot contain a virus or steal personal
information stored on a hard drive– Can pose a privacy risk
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Privacy Attacks (cont’d.)• Adware
– Software that delivers advertising content – Unexpected and unwanted by the user– Can be a privacy risk
• Tracking function• Popup
– Small Web browser window – Appears over the Web site
that is being viewed
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Attacks while Surfing• Attacks on users can occur while
pointing the browser to a site or just viewing a site
• Redirecting Web traffic– Mistake when typing Web address– Attackers can exploit a misaddressed
Web name by registering the names of similar-sounding Web sites
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Attacks while Surfing (cont’d.)
Table 3-1 Typical errors in entering Web addressesSecurity Awareness, 3rd Edition 21
Attacks while Surfing (cont’d.)• Drive-by downloads
– Can be initiated by simply visiting a Web site
– Spreading at an alarming pace– Attackers identify well-known Web site– Inject malicious content
– Zero-pixel IFrame • Virtually invisible to the naked eye
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E-Mail Attacks• Spam
– Unsolicited e-mail– 90 percent of all e-
mails sent can be defined as spam
– Lucrative business
• Spam filters – Look for specific words
and block the e-mail• Image spam
– Uses graphical images of text in order to circumvent text-based filtersSecurity Awareness, 3rd Edition 23
E-Mail Attacks (cont’d.)• Other techniques to circumvent spam filters
– GIF layering– Word splitting– Geometric variance
• Malicious attachments
– E-mail-distributed viruses– Replicate by sending themselves in an e-mail
message to all of the contacts in an e-mail address book
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E-Mail Attacks (cont’d.)• Embedded hyperlinks
– Clicking on the link will open the Web browser and take the user to a specific Web site
– Trick users to be directed to the attacker’s “look alike” Web site
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Figure 3-12 Embedded hyperlink
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Internet Defenses• Several types
– Security application programs– Configuring browser settings
– Using general good practices
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Defenses Through Applications• Popup blocker
– Separate program or a feature incorporated within a browser
– Users can select the level of blocking• Spam filter
– Can be implemented on the user’s local computer and at corporate or Internet Service Provider level
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Walrus Break
Defenses Through Applications (cont’d.)
• Spam filter (cont’d.)– E-mail client spam blocking features
• Level of spam e-mail protection• Blocked senders (blacklist) • Allowed senders (whitelist)
• Blocked top level domain list– Bayesian filtering
• User divides e-mail messages into spam or not-spam
• Assigns each word a probability of being spam– Corporate spam filter
• Works with the receiving e-mail serverSecurity Awareness, 3rd Edition 30
Defenses Through Applications (cont’d.)
Figure 3-16 Spam filter on SMTP server
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Defenses Through Applications (cont’d.)• E-mail security settings
– Configured through the e-mail client application
• Read messages using a reading pane• Block external content• Preview attachments• Use an e-mail postmark
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Defenses Through Browser Settings• Browsers allow the user to
customize security and privacy settings
• IE Web browser defense categories:– Advanced security settings
• Do not save encrypted pages to disk• Empty Temporary Internet Files folder
when browser is closed• Warn if changing between secure and not
secure modeSecurity Awareness, 3rd Edition 33
Defenses Through Browser Settings (cont’d.)
• IE Web browser defense categories (cont’d.):– Security zones
• Set customized security for these zones • Assign specific Web sites to a zone
– Restricting cookies
• Use privacy levels in IE
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Defenses Through Browser Settings (cont’d.)
Table 3-3 IE Web security zones
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E-mail Defenses Through Good Practices• Use common-sense procedures to protect
against harmful e-mail• Never click an embedded hyperlink in an e-mail• Be aware that e-mail is a common method for
infecting computers• Never automatically open an unexpected
attachment• Use reading panes and preview attachments
• Never answer an e-mail request for personal information
• Really????
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Internet Defense Summary
Table 3-4 Internet defense summary
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Summary
• Internet composition– Web servers– Web browsers
• Internet technologies– HTML– JavaScript
– Java– ActiveX
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Summary (cont’d.)• Privacy risk
– Cookies– Adware
• Security risk– Mistyped Web address
– Drive-by downloads• Email security
– Spam– Attachments
• Security applications
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Walrus Risk
• Walrus Risk – They may look cute, but walruses are dangerous. They can poke your eyes out with their tusks!