Home > Articles > Security > Software Security

Trojan Horses

  • Print
  • + Share This
This chapter is from the book

This chapter is from the book

Wrap Stars

Be afraid. Be very afraid.

—The movie, The Fly, 1986

Bad guys' Trojan horse ruses aren't limited to just playing games with names. Many attackers also combine their malicious code with an innocuous program to create a nice, cozy-looking package. By grafting together two programs, one malicious and one benign, an attacker can more easily trick unsuspecting users or administrators into running or ignoring the combined result. When unsuspecting victims receive the combined package and run it, the malicious executable embedded in the package will typically run first. Of course, the vast majority of back-doors don't display anything on the screen, so the victim will not see anything during this step, which usually takes less than a second. After the backdoor is firmly lodged on the victim machine, the benign program runs. For example, an attacker might take the Tini backdoor we briefly mentioned in Chapter 5 and combine it with Internet Explorer. Given Tini's small size, the resulting program would be only 3 kilobytes larger than the original browser.

To marry two executables together, an attacker uses a wrapper tool. The computer underground uses several terms to refer to these tools, including wrappers, binders, packers, EXE binders, and EXE joiners. Figure 6.6 illustrates how an attacker uses a wrapper program. In essence, these wrappers allow an attacker to take any executable back-door program and combine it with any legitimate executable, creating a Trojan horse without writing a single line of new code! Even the most inexperienced attacker can easily create Trojan horses using this technique. This is the stuff script kiddie attackers fantasize about.

For an analogy of the operation of wrapper programs, consider the classic movie The Fly. As you might recall, in that epic feature, a scientist tests his new teleporter invention to whisk himself across his laboratory at the speed of light. Sadly, a simple housefly zooms into the teleporter pod just as he initiates his first short journey. The machine cannot handle

Figure 6Figure 6.6 Wrapper programs: Two programs enter and one program leaves with the combined functionality of both input programs.

two living beings in a pod, so it just combines the scientist and the fly at their most fundamental level into one very ghastly mutant combination of the two. That's essentially what wrapper tools do: combine two or more separate programs at a fundamental level into one package.

Wrapper Features

Some wrappers allow for combining two, six, nine, or even an arbitrary number of programs together. Others allow for the addition of static files into the mix. When the wrapper is run, it executes all included programs, and also unloads the bundled static files into the attacker's chosen places on the file system. With such capabilities, these wrappers are actually becoming the functional equivalent of souped-up install shields and SetUp programs.

For most of the popular wrapper tools available today, when a combined package file is executed, the malicious program and benign program will each show up as separate running processes in Windows Task Manager or Fport output. The two programs only live together in the file on the hard drive. When a user is duped into running the package, the two wrapped programs become two separate processes. Therefore, to hide the malicious processes, attackers use wrappers together with the deceptive naming schemes we discussed in the last section.

Some wrappers go even further by encrypting the malicious code portion of the resulting package, so that antivirus programs on the target system have more difficulty detecting the malicious program. Of course, to make the malicious program run on its target, the wrapper must add a decryption routine to the resulting package. Antivirus programs therefore look for the decryption code added by these popular wrapping tools. Attackers raise the bar by morphing the decryption code so that it dynamically alters itself to evade detection, using polymorphic coding techniques, as we discussed in Chapter 2.

The computer underground has released dozens of wrapper programs available for free download from the Internet. Table 6.4 shows some of the most popular and powerful wrapper programs available today. To analyze these and other wrapper tools in more detail, you can check out http://www.tlsecurity.net/exebinder.htm, a comprehensive Web site devoted to the fine art of wrappers. It's important to note that not all of these programs are inherently evil. They also have a variety of entirely legitimate uses for packaging and distributing useful software, not just Trojan horses.

Table 6.4 Popular Wrapper Tools

Wrapper Tool Name

Function of Wrapper Tool

AFX File Lace

This wrapper encrypts an executable and appends it to the end of another, unencrypted executable.

EliteWrap

This program is the premier wrapper tool, with gobs of features, including:

The ability to bind together an unlimited number of executables.

A function to start programs in a specified order, with each program waiting for the other programs ahead of it to finish running before executing itself.

Built-in integrity checks to make sure the package hasn't been altered.

Exe2vbs

This tool converts executable programs (in EXE format) into Visual Basic Scripts (VBSs or VB Scripts). By packing the EXE inside of a VB Script, the attacker might be able to transmit a Trojan horse through e-mail filtering programs that block standard EXEs, but allow VB Scripts to pass through.

PE Bundle

This program bundles together an executable with all the DLLs required by that executable to run. With this combined package, the malicious software will be able to run on the target system even if some critical DLLs are not installed there.

Perl2Exe

Using this tool, a developer can create standalone programs originally written in the Perl scripting language that do not require a Perl interpreter to run. Also, the original Perl code isn't included inside the resulting executable, making reverse engineering the functionality of the executable code significantly more difficult than simply analyzing more easily understood Perl scripts. This nifty tool is available for both Windows and UNIX, turning a Perl script into an executable binary program. Binary executables can be created that will run on Windows or UNIX.

Saran Wrap

This easy-to-use GUI-based wrapper combines two executables together.

TOPV4

This so-called Teflon Oil Patch program combines up to nine executables together and sports a simple GUI.

Trojan Man

This wrapper combines two programs, and also can encrypt the resulting package in an attempt to foil antivirus programs.


Wrapper Defenses

To defend your systems against attacks involving Trojan horses created with wrappers, antivirus tools are really your best bet. By detecting the malicious code wrapped into a combination package and preventing its installation, antivirus tools stop the vast majority of these problems. Following the antivirus recommendations we discussed in Chapter 2 goes a long way in dealing with this problem.

  • + Share This
  • 🔖 Save To Your Account

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.

Overview


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information


To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information


Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children


This site is not directed to children under the age of 13.

Marketing


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information


If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information


Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents


California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure


Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact


Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice


We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020