2 cissp ® Official Study Guide Eighth Edition

Macro Viruses
Many common software applications implement some sort of scripting 
functionality to assist with the automation of repetitive tasks. These functionalities often 
use simple, yet powerful programming languages such as Visual Basic for Applications 
(VBA). Although macros do indeed offer great productivity-enhancing opportunities 
to computer users, they also expose systems to yet another avenue of infection—macro 
viruses. 
Macro viruses
fi rst appeared on the scene in the mid-1990s, utilizing crude technologies 
to infect documents created in the popular Microsoft Word environment. Although they 
were relatively unsophisticated, these viruses spread rapidly because the antivirus com-
munity didn’t anticipate them, and therefore antivirus applications didn’t provide any 
defense against them. Macro viruses quickly became more and more commonplace, and 
vendors rushed to modify their antivirus platforms to scan application documents for mali-
cious macros. In 1999, the Melissa virus spread through the use of a Word document that 
exploited a security vulnerability in Microsoft Outlook to replicate. The infamous I Love 
You virus quickly followed on its heels, exploiting similar vulnerabilities in early 2000, 
showing us that fast-spreading viruses have plagued us for nearly 20 years. 
Macro viruses proliferate because of the ease of writing code in the 
scripting languages (such as VBA) utilized by modern productivity 
applications.

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Chapter 21 
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Malicious Code and Application Attacks
After a rash of macro viruses in the late part of the twentieth century, productivity soft-
ware developers made important changes to the macro development environment, restrict-
ing the ability of untrusted macros to run without explicit user permission. This resulted in 
a drastic reduction in the prevalence of macro viruses.