Cryptography CS 110 Fall 2005. From last class… Instant messanger systems Instant messanger...

CryptographyCryptography

CS 110CS 110

Fall 2005Fall 2005

From last class…From last class…

Instant messanger systemsInstant messanger systems• Unsafe links on AIM profilesUnsafe links on AIM profiles• Requests from “buddies” to open Requests from “buddies” to open

messages containing picturesmessages containing pictures

Security problems of interestSecurity problems of interest

confidentiality - protect info content from confidentiality - protect info content from unwarranted observation unwarranted observation

integrity - protect info accuracy integrity - protect info accuracy availability - ensure information delivery availability - ensure information delivery

authentication - assure identity of user (sender) authentication - assure identity of user (sender) • non-repudiation - protect from deniabilitynon-repudiation - protect from deniability

access control - control access to access control - control access to info/resources info/resources

Policies:

Problems that arise in implementation:

AttacksAttacks

interception - of information-traffic, interception - of information-traffic, breaches confidentialitybreaches confidentiality

interruption - of service, availabilityinterruption - of service, availability modification - of information, i.e. modification - of information, i.e.

loss of integrityloss of integrity fabrication - of information, fabrication - of information,

destroys authenticitydestroys authenticity

Response?Response?

identify key assets identify key assets evaluate threat posed to assets evaluate threat posed to assets implement suitable countermeasures implement suitable countermeasures manage implementation manage implementation cryptographycryptography is a key technology is a key technology

• Note – not a “perimeter defense” Note – not a “perimeter defense” technologytechnology

What’s cryptographyWhat’s cryptography

cryptography is the study of secret cryptography is the study of secret ((cryptocrypto-) writing (--) writing (-graphygraphy) )

concerned with developing algorithms concerned with developing algorithms to: to: • concealconceal the content of a message from all the content of a message from all

except the sender & recipient (secrecy or except the sender & recipient (secrecy or confidentiality) confidentiality)

• verifyverify the correctness of a message or its the correctness of a message or its sender to the recipient (integrity & sender to the recipient (integrity & authentication) authentication)

A few termsA few terms

cryptographycryptography • the art or science of transforming an the art or science of transforming an

intelligible message into one that is intelligible message into one that is unintelligible, and then transforming that unintelligible, and then transforming that message back to original form message back to original form

plaintextplaintext • the original intelligible message the original intelligible message

ciphertextciphertext • the transformed messagethe transformed message


keykey • critical (secret) information used in the critical (secret) information used in the

cipher & known only to the sender & cipher & known only to the sender & receiver receiver

Symmetric – shared Symmetric – shared Asymmetric – public/privateAsymmetric – public/private

TransformationsTransformations

codecode • an algorithm for transforming an intelligible an algorithm for transforming an intelligible

message into an unintelligible message using message into an unintelligible message using a code-booka code-book

encryptionencryption • applying a mathematical function mapping applying a mathematical function mapping

plaintext to ciphertext using the specified plaintext to ciphertext using the specified key:key:

C = EC = EKK(P)(P)


cryptanalysiscryptanalysis (codebreaking) (codebreaking) • the study of methods for transforming an the study of methods for transforming an

unintelligible message back into an unintelligible message back into an intelligible message without knowledge of intelligible message without knowledge of the keythe key

SteganographySteganography

embed message in innocuous settingembed message in innocuous setting

My Special Friend,

Our speaker today in class today is exciting, & I know that the next speaker is even better. I need to report to you that next class is the mid-term exam. Well, there is only one mid-term! YEAH!!! Well that is it for now. ………...

Two crypto techniquesTwo crypto techniques

PermutationPermutation

SubstitutionSubstitution

““Staff” cipherStaff” cipher an early Greek transposition cipher:an early Greek transposition cipher:

• cut a narrow strip of paper long enough to cut a narrow strip of paper long enough to write messagewrite message

• wind it around a staff so that adjacent wind it around a staff so that adjacent edges abutedges abut

• write message horizontally down the shaft write message horizontally down the shaft with a character on each wrappingwith a character on each wrapping

• unwindunwind Result: long sequence of seemingly Result: long sequence of seemingly

random lettersrandom letters

The ole alternation trickThe ole alternation trick

write message letters on alternate rows read off cipher by row

Plain = “I CAME I SAW I CONQUERED”

Plain: I A E S W C N U E C M I A I O Q R D Cipher: IAESW CNUE CMIAI OQRD

The ole structured patterns trickThe ole structured patterns trick

write message letters as a matrix read off cipher by some pattern

Plain: I C A M E I S A W I C O N Q U E R D A B Cipher: diagonals, concentric circle, in and out, etc

The ole mirror trickThe ole mirror trick

write the message backwards

Plain: I CAME I SAW I CONQUERED Cipher: DEREU QNOCI WASIE MACI

………and speaking of J. Caesar

Two crypto techniquesTwo crypto techniques

PermutationPermutation

SubstitutionSubstitution

Caesar cipher - substitution Caesar cipher - substitution ciphercipher

Julius Caesar invented to transmit military Julius Caesar invented to transmit military information -- 2000 years agoinformation -- 2000 years ago

Map each letter to another -- fixed offset -- Map each letter to another -- fixed offset -- called the translation alphabetcalled the translation alphabet

Alphabets: Plain: A B C D E F G H I J K L M N O P Q R S T UCipher: E F G H I J K L M N O P Q R S T U V W X Y

CipherText: W TI G M E P W T I E O I V G S Q M R K

Caesar cipher - substitution Caesar cipher - substitution ciphercipher

Julius Caesar invented to transmit military Julius Caesar invented to transmit military information -- 2000 years agoinformation -- 2000 years ago

Map each letter to another -- fixed offset -- Map each letter to another -- fixed offset -- called the translation alphabetcalled the translation alphabet

Alphabets: Plain: A B C D E F G H I J K L M N O P Q R S T UCipher: E F G H I J K L M N O P Q R S T U V W X Y

CipherText: W TI G M E P W T I E O I V G S Q M R KP = S P E C I A L S P EA K E R C O M I N G

Cryptanalysis – break Caesar Cryptanalysis – break Caesar ciphercipher

check out brute force cryptanalysis of a Caesar ciphercheck out brute force cryptanalysis of a Caesar cipher

What is the Key?What is the Key? What is the Key size?What is the Key size?

Mono-alphabetic SubstitutionMono-alphabetic Substitution

Use any permutation of the 26 alphabetic charactersUse any permutation of the 26 alphabetic characters• 26! (i.e. 4 x 1026! (i.e. 4 x 102626) possible keys) possible keys• Non-trivial number of optionsNon-trivial number of options• But, regularities of the language give cluesBut, regularities of the language give clues

English, German, Hebrew, Russian – have different characteristics in terms of English, German, Hebrew, Russian – have different characteristics in terms of letter usageletter usage

Language regularitiesLanguage regularities

can base cryptanalysis on frequency of letter occurrencecan base cryptanalysis on frequency of letter occurrence E is most frequent, thenE is most frequent, then T, R, I, N, O, A, S, then …..T, R, I, N, O, A, S, then ….. rarely are J, K, Q X Z usedrarely are J, K, Q X Z used

• E is 25 times more frequent than QE is 25 times more frequent than Q Strategy (for a “long enough” message) is to guess at letter value based on frequency Strategy (for a “long enough” message) is to guess at letter value based on frequency

of appearance in ciphertextof appearance in ciphertext

Language regularities - exampleLanguage regularities - example

Ceasar (Mono alphabetic substitution) Alphabets: Plain: A B C D E F G H I J K L M N O P Q R S T UCipher: E F G H I J K L M N O P Q R S T U V W X Y

CipherText: W TI G M E P W T I E O I V G S Q M R KP = S P E C I A L S P EA K E R C O M I N G

P = S P E C I A L S P EA K E R C O M I N G

Data Encryption Standard (DES)Data Encryption Standard (DES)

Developed by IBM in 1970sDeveloped by IBM in 1970s• Sold to Lloyds of LondonSold to Lloyds of London

US Nat’l Bureau of Standards US Nat’l Bureau of Standards requested a national cipher standardrequested a national cipher standard

National Security Administration National Security Administration (NSA) worked with IBM to refine it(NSA) worked with IBM to refine it

Adopted in 1977 by Nat’l Bureau of Adopted in 1977 by Nat’l Bureau of StandardsStandards

Key PropertyKey Property

AvalancheAvalanche• Small change in plaintext or in key Small change in plaintext or in key

produces significant change in cipertextproduces significant change in cipertext

• Change one bit of plaintext and about Change one bit of plaintext and about half the ciphertext bits will changehalf the ciphertext bits will change

DES StatusDES Status

No weak points have surfacedNo weak points have surfaced DES is widely usedDES is widely used 1994, Nat’l Institute of Standards and 1994, Nat’l Institute of Standards and

Technology reaffirmed its use for Technology reaffirmed its use for federal usefederal use• Recommended for all but “classified”Recommended for all but “classified”

DES key lengthDES key length

Increased computing has made a 56-bit Increased computing has made a 56-bit key susceptible to exhaustive key searchkey susceptible to exhaustive key search• 1997 – a few months were needed by a large 1997 – a few months were needed by a large

network (70,000) of computers to break DES. network (70,000) of computers to break DES. $10,000 prize claimed$10,000 prize claimed

• 1998 – Electronic Frontier Foundation broke 1998 – Electronic Frontier Foundation broke DES in a few daysDES in a few days

• 1999 – A break accomplished in 22 hours1999 – A break accomplished in 22 hours DES with larger keys is still used and it DES with larger keys is still used and it

works wellworks well

Public Key EncryptionPublic Key Encryption

Alice wishes to communicate a secret Alice wishes to communicate a secret message to Bobmessage to Bob

Bob will then replyBob will then reply

Symmetric Key SystemSymmetric Key System

Alice and Bob have common knowledge of Alice and Bob have common knowledge of a single keya single key

Alice puts message in box and locks with a Alice puts message in box and locks with a padlock for which she has a keypadlock for which she has a key

She sends the box to Bob in regular mailShe sends the box to Bob in regular mail Bob has identical copy of Alice’s key and Bob has identical copy of Alice’s key and

uses it to open the boxuses it to open the box He uses same padlock for sending his He uses same padlock for sending his

response back to Aliceresponse back to Alice

Symmetric Key RisksSymmetric Key Risks

How are the keys distributed?How are the keys distributed?• Through mail?Through mail?• Stolen/copied in the mail?Stolen/copied in the mail?

If key is stolen/copied, all If key is stolen/copied, all communications are (unknowingly) communications are (unknowingly) compromisedcompromised• All participants must synchronize and All participants must synchronize and

get a new keyget a new key

Asymmetric Public KeyAsymmetric Public Key

Bob and Alice have separate Bob and Alice have separate padlockspadlocks

Alice asks Bob to send his open Alice asks Bob to send his open padlock to her through regular mailpadlock to her through regular mail

Alice uses Bob’s lock to secure the Alice uses Bob’s lock to secure the box containing her message and she box containing her message and she mails it to Bobmails it to Bob

Upon receiving the box, Bob uses his Upon receiving the box, Bob uses his key to unlock itkey to unlock it

Advantages of Asymmetric Public Advantages of Asymmetric Public KeyKey

No need to send keys to one anotherNo need to send keys to one another Third party cannot copy key while in Third party cannot copy key while in

transittransit One stolen key only compromises One stolen key only compromises

part of the communicationpart of the communication

Public-key EncryptionPublic-key Encryption

It’s annoying for Bob to send his It’s annoying for Bob to send his padlock to Alicepadlock to Alice

Instead, Bob sends instructions for Instead, Bob sends instructions for how Alice can build a padlock that how Alice can build a padlock that will only be open-able by Bobwill only be open-able by Bob• Note these instructions cannot give Note these instructions cannot give

away secret of Bob’s keyaway secret of Bob’s key


Alice has two keys (strings of letters) Alice has two keys (strings of letters) • Public key that she freely shares with Public key that she freely shares with

the worldthe world• Private key that only she knowsPrivate key that only she knows

Messages encrypted with Alice’s Messages encrypted with Alice’s public key are only decipherable by public key are only decipherable by Alice’s private keyAlice’s private key


Alice can send message encrypted Alice can send message encrypted using her private keyusing her private key

Bob can decode message using Bob can decode message using Alice’s public keyAlice’s public key

Bob is assured message he reads Bob is assured message he reads was authored by Alicewas authored by Alice

Is Public Key Crypto Secure?Is Public Key Crypto Secure? A 128 bit A 128 bit key key would be a number between 1 and would be a number between 1 and

340,282,366,920,938,000,000,000,000,000,000,000,000340,282,366,920,938,000,000,000,000,000,000,000,000 How many prime numbers are between 1 and this number?How many prime numbers are between 1 and this number?

• approximately n / ln(n) which is about 2^128 / ln( 2^128 ) = approximately n / ln(n) which is about 2^128 / ln( 2^128 ) = 3,835,341,275,459,350,000,000,000,000,000,000,0003,835,341,275,459,350,000,000,000,000,000,000,000

How long would it take to find all of these prime numbers if How long would it take to find all of these prime numbers if you could calculate you could calculate one trillionone trillion of these numbers per second? of these numbers per second?• More than More than 121,617,874,031,562,000 years121,617,874,031,562,000 years (i.e., about 10 million (i.e., about 10 million

times longer than the universe has existed so far.) times longer than the universe has existed so far.) • Reference: Reference: http://www.livinginternet.com/?i/is_crypt_pkc_inv.htmhttp://www.livinginternet.com/?i/is_crypt_pkc_inv.htm

Answer – Yes, but know its limitations (e.g. plaintext attacks, Answer – Yes, but know its limitations (e.g. plaintext attacks, block sizes, etc.)block sizes, etc.)

http://www.livinginternet.com/?i/is_crypt_pkc_inv.htm

Weakness of Public-key SystemWeakness of Public-key System

Man-in-the-middle AttackMan-in-the-middle Attack• Communication of Alice’s public key is Communication of Alice’s public key is

intercepted and changed to a new public intercepted and changed to a new public key that matches interceptors private key that matches interceptors private keykey

• Interceptor decodes the message to Interceptor decodes the message to read it and re-encodes it using Alice’s read it and re-encodes it using Alice’s public key before sending on to herpublic key before sending on to her

Trusted key distributionTrusted key distribution

Trusted Key DistributionTrusted Key Distribution

Companies exist to manage key Companies exist to manage key distributiondistribution• Microsoft “offered” to do this with a Microsoft “offered” to do this with a

system called system called PassportPassport

• Business model… Microsoft creates a Business model… Microsoft creates a standard for secure communication and standard for secure communication and sets prices at monopolist levelssets prices at monopolist levels


US GovernmentUS Government

• Do you trust them?Do you trust them?• They are very interested in having the They are very interested in having the

power to control keys so they can listen power to control keys so they can listen to any messageto any message


RSA: Rivest, Shamir, AdelmanRSA: Rivest, Shamir, Adelman VerisignVerisign PGP: Pretty Good PrivacyPGP: Pretty Good Privacy

Breaking RSABreaking RSA RSA inventors offered $100 reward RSA inventors offered $100 reward

for finding a plaintext sentence for finding a plaintext sentence enciphered via RSAenciphered via RSA

public key had 129 decimal digits (public key had 129 decimal digits (~ 428 bits~ 428 bits))

RSA predicted 40 quadrillion years RSA predicted 40 quadrillion years was neededwas needed

1994 -- a group claimed the prize 1994 -- a group claimed the prize after 8 months of work (1600 after 8 months of work (1600 computers used)computers used)

Security and the WebSecurity and the Web

HTTPSHTTPS• Uses port 443 (not 80)Uses port 443 (not 80)• Security protocol is determined by your Security protocol is determined by your

browser and the serverbrowser and the server• Online vendors may establish contract Online vendors may establish contract

with Verisign to handle securitywith Verisign to handle security A form of public-key encryption secures the A form of public-key encryption secures the

transactiontransaction

ReviewReview

AdwareAdware VirusesViruses WormsWorms

ReviewReview

Email Spoofing Email Spoofing • falsified senderfalsified sender

Email Phishing Email Phishing • obfuscate HTML to trick you into obfuscate HTML to trick you into

submitting private info through submitting private info through deceptive web pagesdeceptive web pages

ReviewReview

Openness in desktop computersOpenness in desktop computers• You permit lots of programs to You permit lots of programs to

read/write data to your hard drive and read/write data to your hard drive and memorymemory

• Computer “listens” for packets on many Computer “listens” for packets on many portsports of its internet connection of its internet connection

http, itunes, email, IM, homeDir, …http, itunes, email, IM, homeDir, … Programs that monitor the ports for packets Programs that monitor the ports for packets

are supposed to be failsafeare supposed to be failsafe Flaws are discovered and exploitedFlaws are discovered and exploited

November 8, 2005November 8, 2005

Three image-rendering flaws in the Three image-rendering flaws in the Windows OS could put millions of Windows OS could put millions of Internet-connected users at risk of PC Internet-connected users at risk of PC takeover attacks.takeover attacks.

The flaws could be exploited by any The flaws could be exploited by any software that displays images, software that displays images, including … Outlook, Word, and including … Outlook, Word, and Internet Explorer.Internet Explorer.

http://www.eweek.com/article2/0,1895,1883850,00.asp


The bugs are considered particularly The bugs are considered particularly dangerous because users could be at dangerous because users could be at risk merely by browsing to a risk merely by browsing to a malicious rigged site with rigged malicious rigged site with rigged image files, or by displaying images image files, or by displaying images in the preview pane of an e-mail in the preview pane of an e-mail programprogram


Any program that renders WMF or EMF Any program that renders WMF or EMF images on the affected systems images on the affected systems could be vulnerable to this attack. could be vulnerable to this attack. An attacker who successfully exploits An attacker who successfully exploits this vulnerability can take complete this vulnerability can take complete control of an affected systemcontrol of an affected system


The bulletin also addresses two The bulletin also addresses two separate unchecked buffers in the separate unchecked buffers in the way the OS renders WMF and EMF way the OS renders WMF and EMF images.images.

March 29, 2005March 29, 2005

A similar flaw was detectedA similar flaw was detected The hackers corrupted the banner The hackers corrupted the banner

images of an advertising companyimages of an advertising company 100s of sites used those banners100s of sites used those banners Microsoft took 90 days (?) to release Microsoft took 90 days (?) to release

a “patch” because of the intricate a “patch” because of the intricate nature of Windows and the extensive nature of Windows and the extensive testing requiredtesting required

Today’s NewsToday’s News

Detect severity of earth quake in first Detect severity of earth quake in first 1.5 seconds1.5 seconds

Send immediate warning to San Send immediate warning to San FranciscoFrancisco

Automatically stop trains and shut Automatically stop trains and shut down critical systems to protect down critical systems to protect themthem

Would you trust it?Would you trust it?

OnwardOnward

CookiesCookies Web BugsWeb Bugs More virusesMore viruses

CookiesCookies

Cookies are somewhat controversialCookies are somewhat controversial• Websites can used them for legitimate Websites can used them for legitimate

reasonsreasons• They can be used for the wrong reasonsThey can be used for the wrong reasons• In any case, they are a In any case, they are a fact of lifefact of life of web of web

browsingbrowsing Cookies allow a web-server to:Cookies allow a web-server to:

• Track your visits to the siteTrack your visits to the site• Learn and remember info about youLearn and remember info about you• Store info on your computerStore info on your computer

http://vreport.capaho.com/demo.html

What Is a Cookie?What Is a Cookie? A small piece of information stored by A small piece of information stored by

your web-browser on your PC when your web-browser on your PC when you visit a siteyou visit a site

What’s stored:What’s stored:• A URL related to the site you visitedA URL related to the site you visited• A name/value pair (the information A name/value pair (the information

content)content)• (Optional) An expiration date(Optional) An expiration date

Why is it a “cookie”? Why is it a “cookie”? • An old CS term for a chunk of data used An old CS term for a chunk of data used

obscurelyobscurely

Reminder: Web Browser Reminder: Web Browser and Server Interactionand Server Interaction

User types URL or clicks linkUser types URL or clicks link Browser sends a Browser sends a get-pageget-page request for request for

that URL to web-serverthat URL to web-server Web-server finds HTML file (and Web-server finds HTML file (and

related files)related files) Web-server sends these back to Web-server sends these back to

browserbrowser Browser processes HTML and displays Browser processes HTML and displays

pagepage

Cookies: Web-servers Store Cookies: Web-servers Store Some Info on your PCSome Info on your PC

When sending back a page, When sending back a page, server alsoserver also sendssends a cookiea cookie

Your browser stores it on your PCYour browser stores it on your PC Later, you visit the same siteLater, you visit the same site

• You request a page there You request a page there andand your browser has your browser has earlier stored a cookie matching that URLearlier stored a cookie matching that URL

• Browser sends URL Browser sends URL andand cookie cookie to web-server to web-server• Web-server processes cookieWeb-server processes cookie

May return updated cookies with pageMay return updated cookies with page

Normally browsing the Normally browsing the web is "stateless"web is "stateless"

““Stateless” means “no memory”Stateless” means “no memory”• Request a page from a server; it sends itRequest a page from a server; it sends it• Later request a 2nd page; the server sends itLater request a 2nd page; the server sends it• The webserver doesn't remember anything The webserver doesn't remember anything

connecting these two requestsconnecting these two requests But, cookies preserve “state.” Server can But, cookies preserve “state.” Server can

connect an early visit with a later visit.connect an early visit with a later visit.• How? Cookie stored a numeric ID number for How? Cookie stored a numeric ID number for

youyou FYI, a server FYI, a server doesdoes “log” requests “log” requests

• what page, what IP address, when, browserwhat page, what IP address, when, browser• But this can’t identify you uniquelyBut this can’t identify you uniquely

Cookies Can Be BeneficialCookies Can Be Beneficial Shopping CartsShopping Carts

• Server creates a cart, stored on the serverServer creates a cart, stored on the server• You visit other pages, but a cookie lets the You visit other pages, but a cookie lets the

server know you’re the person who created server know you’re the person who created that cartthat cart

Other personalizationOther personalization• ““Welcome back, Jane Doe!”Welcome back, Jane Doe!”• ““Items you viewed recently are…”Items you viewed recently are…”

Recognizing legitimate users for a siteRecognizing legitimate users for a site• Register and log-in, but then a cookie means Register and log-in, but then a cookie means

you don’t have to log-in every timeyou don’t have to log-in every time

The Darker Side of CookiesThe Darker Side of Cookies

We assume anonymity on the web, We assume anonymity on the web, right?right?

Do you want someone knowing what Do you want someone knowing what pages you’ve visited?pages you’ve visited?• Cookies allow a website to track what you Cookies allow a website to track what you

visited on that sitevisited on that site• Are they keeping this private? Selling it?Are they keeping this private? Selling it?

Do you even know they’re tracking your Do you even know they’re tracking your visits?visits?

• What are your rights here?What are your rights here?

The Darker Side of Cookies (2)The Darker Side of Cookies (2)

Personalized ads (e.g. the company Personalized ads (e.g. the company DoubleClick)DoubleClick)• Advertising image on a page is really on Advertising image on a page is really on

another serveranother server• You click on the image on the ad-serverYou click on the image on the ad-server• It builds up a profile about you over timeIt builds up a profile about you over time• Deliver ads you want to seeDeliver ads you want to see

When used for authorization, are they When used for authorization, are they secure?secure?

You Have ControlYou Have Control

You can configure your browser to You can configure your browser to handle cookies as you wanthandle cookies as you want

Cookies: Should You Worry?Cookies: Should You Worry? Hard to say…Hard to say…

• Some are quite useful. They allow e-Some are quite useful. They allow e-commerce!commerce!

• Some are sneakySome are sneaky Some anti-spyware tools remove Some anti-spyware tools remove

undesirable cookies (some remove undesirable cookies (some remove harmless ones)harmless ones)

Where We Are in the LectureWhere We Are in the Lecture

Email issuesEmail issues• attachments and email-spoofingattachments and email-spoofing• phishingphishing

CookiesCookies Web-bugsWeb-bugs Viruses in emailViruses in email Spyware (including browser hijacks)Spyware (including browser hijacks)

What’s a Web Bug?What’s a Web Bug? We know visiting a URL “announces” your We know visiting a URL “announces” your

presencepresence If the web page you visit has images, If the web page you visit has images,

those images can be references to other those images can be references to other web pages:web pages:

Consider foobar.html at Consider foobar.html at www.foo.comwww.foo.com• foobar.html includesfoobar.html includes• <img src=“http://www.virginia.edu/rotunda.gif><img src=“http://www.virginia.edu/rotunda.gif>

http://www.foo.com/

What’s a web bugWhat’s a web bug

Something that makes your machine Something that makes your machine execute a execute a get-pageget-page request for a site request for a site you don’t expectyou don’t expect• The server there logs delivery of that The server there logs delivery of that

imageimage May be invisible (hard to see a 1x1 May be invisible (hard to see a 1x1

pixel … VIEW SOURCE)pixel … VIEW SOURCE) Sometimes known as a "clear GIFs", Sometimes known as a "clear GIFs",

"1-by-1 GIFs" or "invisible GIFs“"1-by-1 GIFs" or "invisible GIFs“

http://www.eff.org/Privacy/Marketing/web_bug.htmlhttp://www.eff.org/Privacy/Marketing/web_bug.html

Examples (in HTML)Examples (in HTML)

<img <img src="http://ad.doubleclick.net/ad/pixel.qusrc="http://ad.doubleclick.net/ad/pixel.quicken/NEW" width=1 height=1 icken/NEW" width=1 height=1 border=0>border=0>

<img width='1' height='1' <img width='1' height='1' src="http://www.m0.net/m/logopen02.assrc="http://www.m0.net/m/logopen02.aspp? ? vid=3&catid=370153037&email=SMITHSvid=3&catid=370153037&email=SMITHS%40tiac.net%40tiac.net" alt=" "> " alt=" ">

What Info Can Be Gathered?What Info Can Be Gathered?

Again, the server where the bug lives will Again, the server where the bug lives will log:log:• The IP address of your computer The IP address of your computer • The URL of the page that the Web Bug is located The URL of the page that the Web Bug is located

onon• The URL of the Web Bug imageThe URL of the Web Bug image• The time the Web Bug was viewedThe time the Web Bug was viewed• The type of browser that fetched the Web Bug The type of browser that fetched the Web Bug

imageimage Also possible: Info from any cookie that's Also possible: Info from any cookie that's

on your machineon your machine

Web Bugs on a Web PageWeb Bugs on a Web Page

Using personal info in a cookie, ad Using personal info in a cookie, ad companies can track what pages you companies can track what pages you view over timeview over time• Stores this info in a databaseStores this info in a database• Later used to target specific banners ads Later used to target specific banners ads

for youfor you

How many people view a websiteHow many people view a website

Web Bugs Used in an EmailWeb Bugs Used in an Email

Tells if and when a message was readTells if and when a message was read Links email address with the IP address of Links email address with the IP address of

machine you read mail onmachine you read mail on Within an organization, can tell how often Within an organization, can tell how often

a message is forwarded and reada message is forwarded and read In spam:In spam:

• How many users have seen the spam messageHow many users have seen the spam message• Allows spammers to detect valid email Allows spammers to detect valid email

addressesaddresses

Web Bugs: Legal, Ethical?Web Bugs: Legal, Ethical?

Controversial! Attempt to monitor Controversial! Attempt to monitor you without your knowledgeyou without your knowledge

Legal? Not clearly illegalLegal? Not clearly illegal They They areare used on the websites of used on the websites of

legitimate companieslegitimate companies Privacy policies for websites Privacy policies for websites

generally don't mention thesegenerally don't mention these

Web Bugs: What can you do?Web Bugs: What can you do?

You can't easily identify web bugsYou can't easily identify web bugs New email clients (e.g. Mozilla New email clients (e.g. Mozilla

Thunderbird) do not display images in Thunderbird) do not display images in email that are links to files on external email that are links to files on external sites (see next slide)sites (see next slide)• (Images embedded as part of email message (Images embedded as part of email message

are OK)are OK)• You can click "Show Images" buttonYou can click "Show Images" button• Also nice not to see some images in spamAlso nice not to see some images in spam

Helps to disable and delete cookiesHelps to disable and delete cookies

An Email Client Blocks Remote ImagesAn Email Client Blocks Remote Images

AnonymityAnonymity

Are you really anonymous surfing the Are you really anonymous surfing the web?web?• Someone (corporations and whoever buys their Someone (corporations and whoever buys their

data) is collecting info on your browsingdata) is collecting info on your browsing Do we want:Do we want:

• Tools to “protect” us from this?Tools to “protect” us from this?• Laws against it?Laws against it?• Laws that disclose it’s being done and how the Laws that disclose it’s being done and how the

info is used?info is used?• Users to be aware it’s going on? (Yes!)Users to be aware it’s going on? (Yes!)



CookiesCookies Web-bugsWeb-bugs Viruses in emailViruses in email Spyware (including browser hijacks)Spyware (including browser hijacks)

Anatomy of a virusAnatomy of a virus

How you can be infectedHow you can be infected• By just reading email when…By just reading email when…

you do not keep your software updated!you do not keep your software updated!

Links in E-mailLinks in E-mail

The “data format” of Web pages is HTMLThe “data format” of Web pages is HTML• Controls the formatting of a Web pageControls the formatting of a Web page• Also supports hyperlinks to other pagesAlso supports hyperlinks to other pages• It’s nice when e-mail has this format, right?It’s nice when e-mail has this format, right?

A danger:A danger:• Some links can cause a program to run.Some links can cause a program to run.• Some download files that run on your system.Some download files that run on your system.

An attacker can disguise a link so it looks An attacker can disguise a link so it looks harmless (but…)harmless (but…)

Virus through a Link in an Virus through a Link in an EmailEmail

Link Link seemsseems to be to CS dept. (www.cs.virginia.edu) to be to CS dept. (www.cs.virginia.edu) That’s the That’s the texttext of the link of the link

• It links to someplace elseIt links to someplace else• An attachment that is disguised so it doesn’t appearAn attachment that is disguised so it doesn’t appear• The small box is the only clueThe small box is the only clue

How Can This Virus Get How Can This Virus Get Triggered?Triggered?

Click the link, and it tries to display the Click the link, and it tries to display the hidden attachmenthidden attachment• Only in someOnly in some email clients, i.e. older email clients, i.e. older

versions of Outlookversions of Outlook• Note: This vulnerability has been known!Note: This vulnerability has been known!

Patches available through Windows Update!Patches available through Windows Update! Click and… Congratulations!Click and… Congratulations!

• You’re now infected with a version of the You’re now infected with a version of the Netsky virus!Netsky virus!

What’s Netsky Do?What’s Netsky Do? A mass-mailing worm A mass-mailing worm

• Harvests email addresses from files on your PCHarvests email addresses from files on your PC• Comes with its own mail-server componentComes with its own mail-server component• Now a server on your machine that uses the SMTP Now a server on your machine that uses the SMTP

protocol to send copies of the virus directly to protocol to send copies of the virus directly to others!others!

You’re infected You’re infected andand contagious contagious• You’ll be very popular with your friends and other You’ll be very popular with your friends and other

email contacts!email contacts!• But they should have been running antivirus But they should have been running antivirus

software, and should have kept their systems software, and should have kept their systems updated.updated.

• (Like you should have been.)(Like you should have been.)

LessonsLessons

Use Windows Update to keep your system Use Windows Update to keep your system updatedupdated• AKA keep it “patched”AKA keep it “patched”

You might consider using software that is You might consider using software that is not the major target of virus writersnot the major target of virus writers• Other operating systems (Mac OS, Linux)Other operating systems (Mac OS, Linux)• Other email clients, other browsersOther email clients, other browsers

And And definitelydefinitely install and run anti-virus install and run anti-virus software (next slide)software (next slide)

SolutionsSolutions Antivirus SoftwareAntivirus Software

• Can scan your system: find and remove Can scan your system: find and remove problemsproblems

• Usually only viruses. Sometimes spyware too.Usually only viruses. Sometimes spyware too.• Also, most have Also, most have real-timereal-time protection protection

Checks e-mail as your read it, as you send itChecks e-mail as your read it, as you send it Checks files as you download themChecks files as you download them

• Note: Free for UVa users (see later slide)Note: Free for UVa users (see later slide) Important: run “update” on these to get Important: run “update” on these to get

updated virus definitionsupdated virus definitions



CookiesCookies Web-bugsWeb-bugs Viruses in emailViruses in email Spyware (including Spyware (including

browser hijacks)browser hijacks)

Browser HijackBrowser Hijack

An extremely nasty adwareAn extremely nasty adware Resets homepage to a particular siteResets homepage to a particular site

• Ads, porn – something you don’t wantAds, porn – something you don’t want• Any change you make doesn’t affect itAny change you make doesn’t affect it

Software running on your machineSoftware running on your machine• Does the usual adware/spyware stuffDoes the usual adware/spyware stuff• Also changes your browser settingsAlso changes your browser settings• Runs when system starts – changes the Runs when system starts – changes the

settings backsettings back

Spyware is a Common Spyware is a Common Problem!Problem!

Recall earlier study of users:Recall earlier study of users:

80% had spyware on their PCs80% had spyware on their PCs

(What about you?)(What about you?)

SolutionsSolutions Anti-spyware softwareAnti-spyware software

• Scans your system, removes problemsScans your system, removes problems• Some have real-time protection, most don’t.Some have real-time protection, most don’t.

Important (again): run “update” on these Important (again): run “update” on these to get most recent spyware definitionsto get most recent spyware definitions

Another option: Security Suites ($60-$70)Another option: Security Suites ($60-$70)• Include antivirus, maybe anti-spyware softwareInclude antivirus, maybe anti-spyware software• Also includes a firewallAlso includes a firewall• May include spam filtering, parental controlMay include spam filtering, parental control

Getting Software at UVaGetting Software at UVa

ITC Downloads: ITC Downloads: http://www.itc.virginia.eduhttp://www.itc.virginia.edu• Norton AntivirusNorton Antivirus• SpySweeper (up to 3 machines)SpySweeper (up to 3 machines)• Free for UVa users!Free for UVa users!

This is a This is a wonderfulwonderful deal for students and deal for students and staff.staff.

Don’t be foolish! Please go install these! Don’t be foolish! Please go install these! • And keep things updated. Practice good habits.And keep things updated. Practice good habits.

http://www.itc.virginia.edu/

Anti-Virus SW For Your Anti-Virus SW For Your Non-UVa FriendsNon-UVa Friends

Free anti-virus software through websitesFree anti-virus software through websites• http://http://housecall.trendmicro.comhousecall.trendmicro.com//• http://http://www.pandasoftware.com/activescanwww.pandasoftware.com/activescan//• These two reviewed recommended by reliable These two reviewed recommended by reliable

magazinesmagazines These run their program on your PC from These run their program on your PC from

their websitetheir website• Scans your system and identifies problemScans your system and identifies problem

Does not include real-time protectionDoes not include real-time protection

http://housecall.trendmicro.com/



http://www.pandasoftware.com/activescan/



Anti-Spyware SW For Your Anti-Spyware SW For Your Non-UVa FriendsNon-UVa Friends

Good Good freefree utilities to find and remove utilities to find and remove spywarespyware• Lavasoft Adware: Lavasoft Adware: http://http://www.lavasoftusa.comwww.lavasoftusa.com//• Spybot Search & Destroy:Spybot Search & Destroy:

http://http://www.spybot.infowww.spybot.info Download, install, and run periodicallyDownload, install, and run periodically Updates:Updates:

• Must get updates of definitions for Antivirus Must get updates of definitions for Antivirus and spyware removal toolsand spyware removal tools

• Often free: use update facility in the toolOften free: use update facility in the tool

http://www.lavasoftusa.com/



http://www.spybot.info/

http://www.spybot.info/

SpySweeper in ActionSpySweeper in Action

Scanning Your PCScanning Your PC

Removing What It FoundRemoving What It Found

The ResultsThe Results

Everything That Looks Like Spyware Everything That Looks Like Spyware Removal Is Removal Is NotNot Spyware Removal Spyware Removal

•Email arrives with animated GIF file.

• Click on OK – you’re really clicking on the web-link associated with that image. Uh oh.

Final WordsFinal Words Cookies and web bugs raise privacy Cookies and web bugs raise privacy

issuesissues Malware: it’s a nasty world out there!Malware: it’s a nasty world out there!

Protect yourself with:Protect yourself with:• UnderstandingUnderstanding• Tools (anti-virus SW, anti-spyware SW)Tools (anti-virus SW, anti-spyware SW)

Practice good habits:Practice good habits:• Be suspicious and cautiousBe suspicious and cautious• Install, run, and update toolsInstall, run, and update tools• Keep your operating system updatedKeep your operating system updated

Cryptography CS 110 Fall 2005. From last class… Instant messanger systems Instant messanger...

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