By some estimates,
roughly three out of every four viruses is actually a macro written for
Microsoft Word or Excel. These macros are executed automatically
when the documents that contain them are opened, at which point they
attach themselves to the global template so that they can infect every
document you subsequently open and save. Both Word and Excel have
security features that restrict this feature, but these measures are clumsy
and most people disable them so they can work on the rest of their documents.
In other words, don??™t rely on the virus protection built in to
Microsoft Office to eliminate the threat of these types of viruses.
280 | Chapter 6: Troubleshooting
Peer-to-peer (P2P) file sharing
Napster started the P2P file-sharing craze years ago, but modern file
sharing goes far beyond the trading of harmless music files. It??™s estimated
that some 40% of the files available on these P2P networks contain
viruses, Trojan horses, and other unwelcome guests, but even these
aren??™t necessarily the biggest cause of concern.
To facilitate the exchange of files, these P2P programs open network ports
(Chapter 7) and create gaping holes in your computer??™s firewall, any of
which can be exploited by a variety of worms and intruders. And since
people typically leave these programs running all the time (whether they
intend to or not), these security holes are constantly open for business.
But wait...there??™s more! If the constant threat of viruses and Trojan horses
isn??™t enough, many P2P programs themselves come with a broad assortment
of spyware and adware, intentionally installed on your system along
with the applications themselves.
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