McAfee DR SOLOMON S ANTI-VIRUS 8.5 User Manual page 19

Preface
Convergences in the technologies that have resulted from this feverish pace of
invention have given website designers tools they can use to collect and
display information in ways never previously available. Websites soon sprang
up that could send and receive e-mail, formulate and execute queries to
databases using advanced search engines, send and receive live audio and
video, and distribute data and multimedia resources to a worldwide audience.
Much of the technology that made these features possible consisted of small,
easily downloaded programs that interact with your browser software and,
sometimes, with other software on your hard disk. This same avenue served
as an entry point into your computer system for other—less benign—
programs to use for their own purposes.
Java, ActiveX, and scripted objects
These programs, whether beneficial or harmful, come in a variety of forms.
Some are special-purpose miniature applications, or "applets," written in Java,
a programming language first developed by Sun Microsystems. Others are
developed using ActiveX, a Microsoft technology that programmers can use
for similar purposes.
Both Java and ActiveX make extensive use of prewritten software modules, or
"objects," that programmers can write themselves or take from existing
sources and fashion into the plug-ins, applets, device drivers and other
software needed to power the web. Java objects are called "classes," while
ActiveX objects are called "controls." The principle difference between them
lies in how they run on the host system. Java applets run in a Java "virtual
machine" designed to interpret Java programming and translate it into action
on the host machine, while ActiveX controls run as native Windows software
that links and passes data among other Windows programs.
The overwhelming majority of these objects are useful, even necessary, parts
of any interactive website. But despite the best efforts of Sun and Microsoft
engineers to design security measures into them, determined programmers
can use Java and ActiveX tools to plant harmful objects on websites, where
they can lurk until visitors unwittingly allow them access to vulnerable
computer systems.
Unlike viruses, harmful Java and ActiveX objects usually don't seek to
replicate themselves. The web provides them with plenty of opportunities to
spread to target computer systems, while their small size and innocuous
nature makes it easy for them to evade detection. In fact, unless you tell your
web browser specifically to block them, Java and ActiveX objects download to
your system automatically whenever you visit a website that hosts them.
User's Guide xix