A white paper on the history and future of malware and how it can affect theApple Mac OS X platform. This document is also available in academy white paper format as a PDF file . Click here to downloaded (1.2 megs).
This document discusses the technologies used in malware. These include viruses, Trojans and worms. The specific intention is to bring forth detailed discussion on how this affects the Apple Mac OS X platform. The document outlines a potential framework for a Mac OS X malware suite. The document closes with recommendations on what Apple Inc, and users of Mac OS X can do to defend against such technology.
This paper was created to outline the results of research performed by the MacForensicsLab.com research and development team. These results are presented to the public in order to raise awareness of the situation and to prompt the relevant responsible parties to address the issues outlined within.
The MacForensicsLab.com staff and SubRosaSoft.com Inc consider it important to bring such discussions out into the public and welcomes all opportunities to discuss the paper on [email protected].
Apple Inc. and all third parties discussed in this paper do not endorse this content and they did not cooperate in the production of this paper. All trademarks contained within this paper remain the property of their respective owners with all rights reserved.
Malware The History And Future
Hacking The Use Of A System Outside Of Its Design
In the early days of computing the term hacker was used to describe those with a deep understanding of the core functionalities that comprised a computer system. These hackers were able to apply this understanding to enable computers to perform in a manner which was previously unimaginable. Therefore, these hackers were a fundamental catalyst for the change and growth of modern computer systems and the Internet.
The term has been degraded over time to be generally limited to someone who targets system security and ways to get around it. In modern times it has come to include people using tools they did not produce in order to cause damage or nuisance to computer systems.
The Study And Creation Of Malware
The academic world of computer science has been at the forefront of the discussion and definition of malware since the first virus was discovered. Universities became perhaps the first victims of malware and consequently the first defenders against them.
Some notable academics in the early days include:
1980 Jrgen Kraus, a computer science student at the University of Dortmund, wrote his master’s thesis on Selbstreproduktion bei Programmen, [Program Self-Reproduction]. This thesis is the first study to show that certain programs can display behavior similar to that of a biological virus.
Professor Len Adleman, of USC, employs the term virus to describe self-copying programs when discussing them with Fred Cohen, his computer science student.
1981 – 82
Joe Dellinger, a student at Texas A&M University, writes several self-reproducing programs for Apple II disks, naming them Virus 1, Virus 2 and Virus 3.
Apple Computer Inc. had a very strong presence in the academic community throughout the early personal computing era. The use of the Apple platform in the development of malware is an extension of its overwhelming presence in the academic arena.
Hax0r The Growth Of The Script Kiddy Generation
As home computer use grew, a new generation of hackers arose. These young hackers represented a fundamental change in ability, ideology and intent from their predecessors. The new generation of hackers is referred to as script kiddies.
The name script kiddies is a descriptive term, popularized by the original hacking core, as a means to reflect their general disdain of the new generations lack of understanding of the core concepts of computing and their inability to create tools of their own.
Apple Computer Inc. was given the historic honor of being the first computer to bring virus technology into the home when Richard Skrenta wrote Elk Cloner in 1982. This program attached itself to the Apple DOS operating system of the time and spread via floppy disks.
Prior To The Mac
The story of the early years of Apple Computer Inc. and the relationship between the founders Steve Jobs and Steve Wozniak cannot easily be told without including hacking and underground technology. From the days of the BlueBox, a device designed to fool the telephone systems of AT&T into providing free long distance phone calls, through the creation of the first commercial home computer in a garage in what later became known as Silicon Valley.
Apple Inc. and the modern high tech lifestyle we all enjoy today were founded by (so-called) old school hackers.
Figure 2 This blue box, on display at the Computer History Museum was previously owned by co-founder of Apple Computer Inc.  Steve Wozniak. Steve once used this to impersonate Henry Kissinger in a prank call to the Vatican City. The Pope was reportedly asleep. 
The Mac Classic operating system (any version prior to version 10, Mac OS X) enjoyed a long life and a wide user base from the initial release in 1984 to the first desktop version of Mac OS X in March of 2001. This operating system revolutionized the way we work with personal computers offering many of the user interface concepts taken for granted today.
During the lifetime of Mac OS Classic many varieties of malware were developed to take advantage of the user base including some very notorious viruses such as nVir in 1987. The nVir author(s) released the source code for their work resulting in a large proliferation of derivatives causing wide and varied effects in the field.
The wide spread introduction of viruses for Mac OS at this time brought forth the corresponding large number of anti-malware tools that are stillaround today. These tools scan for code found within known viruses and eradicating them when found.
Apple Computer Inc. made changes to the operating system to stop some of the methods used by viruses on Mac. Perhaps the most notable change was to stop autorun, a technology still present on Microsoft Windows that will automatically execute programs when a disk is inserted.
Mac OS X (Including Mac OS X 10.5 Leopard)
All successful, and most plausible, malware attacks on Mac OS X have occurred in the last 2 years with the last quarter of 2007 being particularly prolific. Market penetration and overall sales of the Mac OS X system have directly mirrored development of malware, a phenomenon also demonstrated with other operating systems such as Microsoft Windows. Based on this data there is no reason to believe the trend will not continue as Apple continues to increase their market share.
concept of the economy of scale has historically meant that malware authors
have not previously considered the Mac a viable target. This protection is
being eroded by the increase in size of the Mac user base.
analyst Chris Christiansen is warning Mac users of the growing threat.
Mac users take security too lightly. In fact, most are quite proud of the fact
that they don’t run any security at all,” Christiansen said. “That’s
an open door; at some point it will be exploited.”
users, your days of worry-free web surfing could be numbers. A Mac internet security and privacy software maker has discovered what is believed to be the first professionally crafted in-the-wild malware targeting the Mac Operating system.
A Change In Culture
This century has seen significant changes in the hacking community with an overall trend away from the technology enthusiast to the organized crime rings committing mass fraud and global extortion on the global digital marketplace.
This change in culture has brought with it many changes in focus for the modern malware author.
Malware is now being used to steal information, and thus property, from a users system. These types of attacks range from simply extracting the requisite personal information to assist in identity theft to more complicated attacks known as phishing whereby the malware pretends to be a trusted service such as a bank or service provider in order to steal from an external resource.
DDOS Distributed Denial Of Service
crime groups are using malware in order to extort payment from system owners
and operators. Large collections of infected systems can be used to cause
servers and systems to become inoperable by flooding their connections with
traffic, thus cutting off desirable traffic, or by overwhelming a systems
criminals use malware to convert innocent users systems into virtual soldiers in their army of computers. These armies are
called bots, bot networks, or bot nets, and can sometimes number into the tens
of thousands . This is generally done without the user being aware they
have joined into the network of bots.
Global Cyber Terror
century has seen the rise in state-funded cyberterrorism. There has
become a very high potential for cyberterrorism to impact our economy and our
society in ways that are difficult to define.
Malware The Definition
What Defines A
A virus is a piece of software that attaches itself to another program (the host) then uses the ability of the host program to self-replicate. Stephen Hawking once said that a virus should count officially as a form of life adding  I think it says something about human nature that the only new form of life we have created so far is purely destructive. Weve created life in our own image.
The name for this variety of malware is derived from the Latin word for toxin. The medical community defines a virus is an infectious agent that is unable to replicate or grow outside of a host cell.
How They Replicate
A computer virus will generally execute when the host program is executed. The first priority is to look for additional hosts and to copy itself into them. The second priority is
often, but not always, to execute its payload. Payloads vary heavily from the harmless to full cyber terrorism and have historically included such functions as erasing the entire system, stealing personal information, or simply declaring their existence (digital graffiti).
Macs Are Vulnerable
The primary requirement of a virus is a host program into which it can write itself. The Mac OS X platform makes little or no effort to protect the main applications on the system (in fact, as discussed later, it actually makes it easy through the use of the bundle architecture.)
What Defines A Trojan
A Trojan, or more accurately Trojan Horse, is a piece of software that contains a hidden payload. The word ‘Trojan horse’ is generally attributed to Daniel Edwards of the NSA. He is given credit for identifying the attack form in the report “Computer Security Technology Planning Study”.
The name for this variety of malware is derived from the Greek legend where Odysseus had a giant hollow wooden horse and hid his soldiers inside. The people of Troy believing it to be a gift brought the horse inside their city and their defenses.
What They Do
In computing terms the concept is identical to the legend. The malware is able to enter the users system and bypass security measures be pretending to be something the user wants. Once the user executes the malware on their computer the hidden payload can perform the function desired by the malware author.
Macs Are Vulnerable
The definition of a Trojan makes defense very difficult. The weakness in any system defense starts with the user and a Trojan defines its attack by exploiting that weakness.
Early versions of Mac OS X had little or no protection against a Trojan attack. The effect a Trojan could have on the system was limited to the users data and the applications installed on that computer.
OS X 10.5 Leopard introduces new sandboxing technology to show a dialog box to the user before running any new program downloaded from the Internet. Software downloaded from the Internet, both from the mail and from browser applications, is marked as suspicious and will not be executed until the user clicks on a confirmation dialog box to explicitly allow it to run.
SubRosaSoft.com Inc. extended this paradigm to sandbox all applications, not just ones downloaded from the internet.
Other commercial software vendors (such as Symantec, McAfee, and Intego) offer varying technologies to assist in this area. More information can be found at the companies respective web addresses:
- Intego Virus Barrier (http://www.intego.com)
- McAfee VirusScan(http://shop.mcafee.com)
- Norton AntiVirus (http://shop.symantecstore.com)
What Defines A Computer Worm
A computer worm is similar to a virus in that it is self-replicating, but different in that it does not require a host program to exist. The first computer worm was defined and
produced by researchers Jon A. Hupp and John F. Shoch at Xerox PARC in 1978. The worm was created to search a network to find idle processors so that they could share the processing load of large operations across an entire network, but was self-limited to their own network to avoid accidental global expansion.
What They Do
As with other forms of malware the worm matches many of the characteristics of its biological equivalent. A worm will work its way through a network of computers and resources leaving a copy of itself wherever possible to assist in the dissemination process.
Macs Are Vulnerable
When combined with Trojan and virus technologies, worms can infect entire Mac OS X networks. For example if an initial victim is attacked using a Trojan which infects them with a virus that reproduces the worms throughout their system, thus threatening the entire network. These worms, when executed by automated or viral functions, can be used to reinitiate the Trojan attack on other users Mac OS X Address Book, and the unprotected Applications folder.
Malware How It Can Affect Mac OS X
The current Apple Mac OS X environment has some strengths and weaknesses. It has become an abnormally biased situation in that the strengths are very strong and the weaknesses are becoming increasingly obvious.
Users of Apple Mac OS X have been encouraged by media advertising to believe their systems have never been exposed to malware. This culture has grown to a point where many users believe their systems are invulnerable to malware and always will be.
Inc,. Television Advertisement – I run Mac OS 10 so I dont have to worry about your spyware and viruses
Common attitudes behind this complacency include;
- You need a system pass to infect my Mac.
- There are no malware problems on a Mac.
- Macs are immune to malware.
The result of these ill-founded beliefs is a complacency that seriously compromises the ability of the user to make informed decisions when dealing with a malware threat. This complacency can potentially nullify the effectiveness of the sandboxing technology in OS X 10.5Leopard.
A file extension is designed to tell the system and the user what kind of file they are dealing with. Some examples of system extensions are .exe (a Windows executable program), .app (a Mac OS X executable bundle), and .jpg (a common digital photo format).
Both Microsoft Windows and Mac OS X offer the ability to hide the extension from the user. This is often used to disguise the true nature of file from the user. If this hiding is combined with a less technically-oriented user (the majority of all users) then a Trojan can exploit this to hide its own true nature.
The Bundle Architecture
What It Is
Applications on the Mac OS X system are structured using an architecture called a bundle. A bundle is a special folder that pretends to be a single file. The advantage of this, for programmers, is that it allows multiple resources to be contained in one single folder that is, from the users perspective, indivisible.
It should be noted at this point that Apple Inc. also use the bundle format for many of their pro tools to save documents.
Programmers use these special folders to allow certain resources to be treated as part of the program without the risk of those being separated from the main executable code of a program. Some examples are:
- Multiple executables for different platforms such as Classic Mac OS, PowerPC or
- Multiple language files so that a single copy of the application bundle can be
used in different countries and appear in the native language of that country.
- Graphics, buttons, and media resources used within the application.
- Help files, manuals, etc.
A user is presented with an object that looks like (for example):
The underlying bundle appears to the operating system as follows:
How This Assists Malware
The structure of the bundle architecture makes it easier to piggyback executable code within an existing trusted application by simply renaming the existing executable iTunes found in the MacOS subfolder and inserting a second executable into the MacOS folder with the originals executable name.
When the user executes the bundle (in this case iTunes.app) the virus code would execute instead. The virus would then launch the renamed iTunes executable so that the user would not be aware they had run the wrong program.
Mac OS X also makes use of the bundle architecture for storage of user documents in many modern applications such as iMovie, iDVD, and the many pro tools. These bundles typically have their file extension marked invisible so it is possible to disguise an executable program as a data file for such a tool. These bundles can open both their own malware code as well as the desired real application whilst conserving the look and feel of the real data.
This technology makes the process of creating a virus easier since the bundle architecture greatly assists the process of installing multiple executables into one program. Reproduction is greatly simplified since the same architecture is used on most OS X applications.
Unprotected Application Folder
What It Is
Traditional UNIX systems protect their key executables by using file permissions and storing them inside protected folders (such as /usr/bin).
Mac OS X systems maintain their operating system files in the same protected method that traditional UNIX systems use. The programs (commonly known as Applications) that a user relies upon and considers part of their system such as iTunes, iChat, Keynote, etc. are stored unprotected inside a folder called /Applications. Any program running on a Mac OS X system can write to this folder and to most of the contents therein.
How This Assists Malware
Most common applications running on your Mac can be modified, either by replacing the core executable of that program or adding piggyback executables (viruses) without leaving an obvious trace due to the nature of the bundle architecture.
Centralized Open Address Book
What It Is
A Mac OS X user enjoys the convenience of the Address Book. This centralized database keeps track of all other contacts the user communicates with including their instant messaging addresses, email addresses, phone numbers, physical addresses, etc. The database is open to access from all programs running on the Mac OS X computer.
Programs running on the Mac OS X system can read, write and delete addresses from this database at will.
Addresses that are deleted are not actually removed from the database. Instead they are marked for deletion so that the computer can notify other devices such as cellphones, iPods, and PDAs that the user wants that address deleted.
How This Assists Malware
worm known as ILOVEYOU, the Love Bug worm, or VBS/Loveletter started
arriving in email boxes with an attachment LOVE-LETTER-FOR-YOU.TXT.vbs on May
4th, 2000 . This worm spread itself by interrogating users contacts and emailing copies of itself to everyone it found. On its journey it
is estimated that it infected 10% of all internet-connected
personal computers and caused more than 5 billion dollars in damage.
ILOVEYOU worm only infected computers running Microsoft Windows but the
mechanisms for dissemination exist on Mac OS X:
user base believing themselves safe
- Available open database of contacts
- Ability to write to the Applications
implemented a user-controlled system that sandboxes new applications and warns
users they are about to run a new application. Apple recently introduced
similar technology. It should be noted however that the user is already
complicit with the operation at this point so should not be considered a
reliable security measure.
Anatomy Of A Mac OS X Malware Suite
For the purposes of this discussion this section will be limited to descriptions of malware that does not have a payload. No attempt will be made to damage a users system or gain any resources. All technologies will focus on the delivery mechanism that could be used to attack Mac OS X (and other) users. The aim and purpose here is to outline how a suite might work so that recommendations can be received on how to stop such a suite from being successful. The reader is invited to contact Apple Inc., and/or SubRosaSoft.com Inc. with suggestions.
Initial infection (First Wave) – The Trojan Attack
For a successful infection there would be two goals required by the malware author.
First the infection should distance the author from the first wave victims while simultaneously making that first infection as wide as possible.
Primary consideration in the production of a Trojan horse would be placed on making the user want to accept the Trojan.
The Latin epic poem The Aeneid  describes events between the time of Homers Iliad and Homers Odyssey surrounding the Trojan War. This legendary war between the cities of Sparta and Troy had resulted in a deadlock whereby the defenses of the city were equal to the challenge of the attacking army. The attacking leader, Odysseus, needed to create a gift the defending leader would voluntarily accept inside the city defenses. Realizing the men of troy revered the horse he had a mighty wooden horse made large enough to allow his soldiers to hide inside it and left it at the gate of the city.
Do not trust the horse, Trojans. Whatever it is, I fear the Greeks even when they bring gifts. (Virgil, Aeneid, Book 2, circa 19 BC)
Naught from the Greeks towards me hath sped well. So now I find that ancient proverb true, Foes gifts are no gifts: profit bring they none (Sophocles 496 406 BC, Ajax)
In computing terms this same ruse would be used.
The creation of a helpful freeware tool containing a version of a virus that will infect once then lay dormant to a later date can be hosted on a public site then advertised using one of the many freeware distribution sites such as http://www.VersionTracker.com or http://www.Downloads.com.
In keeping with the primary consideration of this step a malware author would leverage public popularity of fashionable technologies of the time, make a small but helpful enhancement for that technology, and then distribute that tool for free. For example, a small freeware utility that assists in the management of SMS text messages on an iPhone.
The malware authors intent is not to fully disseminate the malware suite but to get a wide enough secondary infection wave ready on a time-delayed basis. This methodology follows the concept of the sleeper cell as defined in the Al Qaeda training manual . The virus contained within this Trojan would infect only the system where the Trojan was executed and make a copy of the virus component into all of the unprotected application bundles on that system. This virus would then sit in a dormant state, execute then quit without further action, until a predetermined later date.
The malware author would ensure that once the Trojan has completed its own initial infection that the Trojan application itself self-inoculates to cover the source of the second (main) deployment wave.
Before the main wave of attack is initiated the author should repost and allow for dissemination of a vaccinated version of the Trojan. At this point the number of suspect applications have been greatly increased while simultaneously removing base suspicion from the originating Trojan. Many of the newly infected applications (hereinafter called the second wave Trojans) are, in fact commonly trusted applications such as the Apple tools and third-party tools found on most computers.)
This attack infrastructure delivers a ready supply chain for the second wave in much the same way as the Ho Chi Minh Trail  provided for the North Vietnamese. It does so by forming a relatively complex web of available infection points that the malware author can control. It also provides for a significant level of overlap and duplication should any one conduit be closed.
Reproduction (Second Wave)
The malware authors goal for the second wave is to greatly increase the number of infections. This wave would be repeated on a fixed schedule until the desired infection ratios have been achieved and the desired payload can be implemented.
The second wave would not proceed until sufficient time has passed from the first wave. This time could be determined remotely by having the virus check an online source for a code to proceed. This approach would give the most flexibility, but also offers the highest risk of discovery. Checking system date and time and waiting for a predetermined moment could also determine this time. This approach would give the most protection from discovery, but also offers the least flexibility.
The malware author would use the users data to prepare ammunition for the second wave. This would contain packages made from their own data that are disguised using the bundle architecture. It might also contain sample programs from the users machines that are determined to be small freeware downloads newly infected by the malware code. Because these payloads are prepared on the users own machines they would not trigger the sandbox protection code found in OS X 10.5 when executed on the users machines.
Now that the malware author is sufficiently distanced from the second wave Trojans, the primary consideration moves to mass production of malware. Traditionally this was achieved by at least two separate methods. In this case the malware author uses both methods together and separately for maximum effect.
- The Virus Approach The malware should look for attached devices and
network volumes and infect every available application bundle with its own
- The Worm Approach The malware should send copies of itself to as many
available recipients as possible.
The virus approach would cause the malware to immediately deploy copies of the pre-prepared payloads onto any removable media or network storage device.
The first application to trigger itself would make use of the open address book database to find potential candidates to send a copy of itself to. Special attention would be made to indicators that the potential recipient is a Mac user such as the content of the headers for incoming emails in the victims inbox. The malware author would benefit from the inherent trust of the secondary wave victim for the first wave victim.
This final dissemination would be done in such a way so as to temporarily self-inoculate the application responsible and to carefully feed the outgoing mail to stop from flooding the victims connection and alerting them. Alternatively it might be done in a massive full frontal attack in the manner performed by the ILOVEYOU virus. This remains the prerogative of the malware author, and our responsibility as an industry, to defend against.
What has been discussed in this section of the document covers the three main definitions of malware and documents how each can apply to Mac OS X.
- The Trojan Attack Pretending to be a gift while hiding
- The Computer Virus Self replicating programs dependent on a host
- Digital Worms Producing and disseminating copies directly without a
It is this authors hope that this will open learned discussion of the topic. It is in no way intended as a manual on how to create such a suite of malware technologies. SubRosaSoft.com Inc. would like to take this opportunity to point out that the dissemination of malware is not only immoral, but also illegal. Please refer to Title 18 U.S.C. 1030 Fraud and related activity in connection with computers  for more information.
For Apple, Inc.
Control The Bundle Architecture
Apple might consider implementing a mechanism whereby a bundle cannot contain more than one executable for any given Contents subfolder. This would reduce the ability of malware authors to piggyback their code inside an otherwise legitimate bundle.
Apple may also wish to discuss disallowing multiple extensions inside a .app bundle. This would reduce the ability of malware authors to disguise executable bundles as data files for their pro tools.
Control Access To The Address Book
This paper recommends Apple should contemplate a similar system to the keychain whereby the address book can be locked unlocked and access to the address book can be restricted to certain applications.
Control Write Access To The Applications Folder And Subfolders Found Therein
Apple may think about making it the default behavior for the system to require admin access to write to this very important folder. Furthermore Apple should make an interface that is easy, obvious, and non-technical to turn this access control on or off.
Extend The OS X 10.5 Leopard Sand Box Concept
Apple might consider extending the built in security functions found in OS X 10.5 to include executable code that is created locally rather than the current restriction to download content only. This would slow down the reproduction of code that has already been authorized by the user.
For Mac OS X users
Read the security guidelines from Apple Inc. found at http://images.apple.com/macosx/pdf/MacOSX_Leopard_Security_TB.pdf
Carefully determine the validity and source of any executables you wish to install and run on your Mac OS X computer.
Install and utilize third-party utilities to monitor for
malware activity. Care should be made to avoid programs that specifically rely on scans for known malware as these tools do not offer protection until it is potentially too late.
Some of the tools to consider include:
- Intego Virus Barrier (http://www.intego.com)
- McAfee VirusScan(http://shop.mcafee.com)
- Norton AntiVirus (http://shop.symantecstore.com)
 Wozniak, S. G.; Smith, G. (2006), iWoz: From Computer Geek to Cult Icon: How I Invented the Personal Computer, Co Founded Apple, and Had Fun Doing It. W. W. Norton &
Company. ISBN 0-393-06143-4.
 US Southern District Court, US New York City Attorneys Office, entered as evidence in Africa embassy bombings. Retrieved November 17, 2007, Al-Qaeda training manual http://www.fas.org/irp/world/para/aqmanual.pdf
 Cornell University Law School, Legal Information Institute. US Code: Title 18 > Part I > Chapter 47 > 1030. Fraud and related activity in connection with computers. http://www4.law.cornell.edu/uscode/18/1030.html