1 of 4 Malicious software, also known as “malware,” is often only a nuisance, but increasingly, malicious software can damage data, computers, and computer networks. Examples include Trojan horses, vandalware, spyware, hoaxes, some viruses—including macro viruses—and worms. All of these terms are explained in the first topic of this guide. Topics in this guide: Types of Malicious Software Learn to Identify Malicious Software Protect Yourself Against Malicious Software Clean Malicious Software from Your Computer Trojan horses are programs that appear harmless at first (they often arrive as an joke or amusing program), but contain a hidden function that creates damage. Unlike viruses, Trojan horses do not attach themselves to files, they simply carry out their malicious instructions. Trojan horses are stand-alone programs that cannot be cleaned and should be deleted when found. Vandalware is software that steals information for monetary gain. Often hidden inside spyware, vandalware includes backdoor Trojan horses (Trojan horses that open a secret door to your computer or network), hacker tools (password crackers, network sniffers, keystroke loggers, and more), remote administration tools (RATs), robots (BOTs), dialers, and tools used to initiate distributed denial of service (DDoS) attacks. Spyware/Adware is any software that secretly gathers user information through a user’s Internet connection, usually for advertising purposes. Once installed, spyware monitors a user’s activity on the Internet and transmits the information secretly to another party. Hoaxes, sometimes called hoax viruses, are fake reports of true viruses. Hoaxes are not real, but they trick people into responding as if a real virus attack were imminent. Hoaxes are damaging because they cause slowdowns in business operations, lost productivity through wasted time, and take up valuable network bandwidth. Computer viruses are software that behave like biological viruses—they attach themselves to a host and replicate, spreading the infection. Some computer viruses are relatively harmless, while others cause serious problems. For a computer program to be classified as a virus, it simply must replicate itself. Macro viruses are viruses that take advantage of the language built into Microsoft ® Visual Basic ® (VB) that allows a sequence of commands (macros) to be inserted into a document or products. Visual Basic macros are commonly used in the Microsoft ® Office suite to automate various tasks. Worms are similar to computer viruses in that they replicate and infect other computers, but they differ from viruses in that they typically replicate without user involvement. Worms are often used to carry other types of malicious software, especially vandalware. Worms prey on system and software vulnerabilities. Types of Malicious Software This document is for informational purposes only. MICROSOFT MAKES NO WARRANTIES, EXPRESS OR IMPLIED, IN THIS DOCUMENT. © 2007 Microsoft Corporation. All rights reserved.

2 of 4 Protect Yourself Against Malicious Software Guard against virus infections and other malicious software with education, antivirus software, and caution when downloading. Run Antivirus Software Download the latest virus update for your software. Once you have installed the latest updates, you will need to run a full-system scan to check for viruses. Your computer runs slowly, or uses more resources than normal. You hear noises—often a churning drive—or see features you didn’t install. messages are sent without your knowledge. Duplicate services or unknown services run on the system. New directories or files appear, or old ones appear changed. Your pointer moves unexpectedly, or windows open by themselves. Your antivirus software, firewall, or other security product shuts down. If spyware has been installed on your computer, you may experience one or more of these symptoms: When you start your computer, or when your computer has been idle for many minutes, your browser opens and displays Web site ads. When you view Web sites, other browser windows open and display Web site ads. Your Internet home page unexpectedly changes. Web pages are unexpectedly added to your Favorites folder. New toolbars are unexpectedly added to your Web browser. You cannot start a program. When you click a link in a program, the link doesn’t work. Your browser suddenly closes or stops responding. It takes a long time to start your computer or to resume using your computer. Program components no longer work. Learn to Identify Malicious Software Malicious software can create symptoms that alert you to its presence. You might be infected if you notice the following behavior: Educate Yourself Stay current on the latest virus information especially about hoax viruses. Remember, if your computer is acting strangely, it doesn’t necessarily mean that you have a virus. Be Careful When You Download Read all dialog boxes carefully and close anything that looks suspicious. When closing dialog boxes or pop-up advertisements, click to close the window. If you're not sure how to safely close a window that has opened in your browser, right-click the browser window icon in your Windows taskbar (usually at the bottom of your screen), and then click Close. The Web is full of ads that feature fake “X” or “Close” or “OK” buttons, and if you click them, you actually open the ad. Here is an example of a fake user interface: This document is for informational purposes only. MICROSOFT MAKES NO WARRANTIES, EXPRESS OR IMPLIED, IN THIS DOCUMENT. © 2007 Microsoft Corporation. All rights reserved.

3 of 4 Click the Microsoft Office button, and then click Options. In the Options window, click Trust Center, and then click Trust Center Settings. Set Security Levels in the 2007 Microsoft Office System One way to protect against macro viruses is to require proof that a macro is from a trusted source. The 2007 release can be set up to require digital signatures for macros and to control what action takes place when it encounters a macro. To set the security level in any applications in the 2007 release: Under Macro Settings click Disable all macros except digitally signed macros, and then click OK Prevent Secret Downloads Some spyware can leave your system susceptible to unwanted downloads (sometimes called “drive-by” downloads). Help prevent this by customizing your browser security settings. In Windows, click Start, and then click Control Panel. Click Network and Internet. Click Internet Options. On the Security tab, click Internet, and then click Custom Level. In the Security Settings – Internet Zone window, click the following settings: 1 2 Download signed ActiveX scripts: Prompt Download unsigned ActiveX scripts: Disable Initialize and script ActiveX not marked as safe for scripting: Disable Installation of desktop items: Prompt Launching programs and files in an IFRAME: Prompt Click OK, and then click OK again Note Internet Explorer alerts you when it attempts to download and install content. This document is for informational purposes only. MICROSOFT MAKES NO WARRANTIES, EXPRESS OR IMPLIED, IN THIS DOCUMENT. © 2007 Microsoft Corporation. All rights reserved.

4 of 4 Clean Malicious Software from Your Computer If your system isn’t already running a virus scan, you should begin a scan. 1 Update your antivirus software. Complete a full-system scan. Download and install a spyware scanner. Tip Visit for more information on spyware, and links to some of the many spyware scanners that are available for download Note If you learn that your computer has been infected by malicious software that compromises your computer, immediately disconnect it from the Internet. It isn’t enough to close your browser—you must unplug your network interface connector, modem, or dial-up phone line. Also, if you identify any malicious software such as a backdoor Trojan, keyboard logger, password stealer, remote access tools (RAT), robots (BOTs), vandalware or spyware, contact your Information Technology (IT) department immediately so the problem can be addressed according your company’s security policies. This document is for informational purposes only. MICROSOFT MAKES NO WARRANTIES, EXPRESS OR IMPLIED, IN THIS DOCUMENT. © 2007 Microsoft Corporation. All rights reserved.