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


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


The World Wide Web (cont’d.)

Figure 3-1 How a browser displays HTML code


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


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


The World Wide Web (cont’d.)

Figure 3-2 HTML document sent to browser


Course Technology/Cengage Learning

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


E-Mail (cont’d.)

Figure 3-3 E-mail transport



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


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)


http://www.experts-exchange.com/images/t10727/Image9.jpg

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


Downloaded Browser Code (cont’d.)

Figure 3-4 JavaScript



• Java– complete programming language

• Java applet– Can perform interactive animations,

immediate calculations, or other simple tasks very quickly

– Unsigned or signed



Figure 3-5 Java applet



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


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


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


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


Attacks while Surfing (cont’d.)

Table 3-1 Typical errors in entering Web addresses


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


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 filters


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


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


Figure 3-12 Embedded hyperlink



Internet Defenses• Several types

– Security application programs– Configuring browser settings– Using general good practices


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


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 server


Defenses Through Applications (cont’d.)

Figure 3-16 Spam filter on SMTP server



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


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 mode


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


Defenses Through Browser Settings (cont’d.)

Table 3-3 IE Web security zones



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????


Internet Defense Summary

Table 3-4 Internet defense summary



Summary

• Internet composition– Web servers– Web browsers

• Internet technologies– HTML– JavaScript– Java– ActiveX


Summary (cont’d.)• Privacy risk

– Cookies– Adware

• Security risk– Mistyped Web address– Drive-by downloads

• Email security– Spam– Attachments

• Security applications


Walrus Risk

• Walrus Risk – They may look cute, but walruses are dangerous. They can poke your eyes out with their tusks!

http://www.travelblog.org/Photos/46524

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