All Categories :
Intranets
Chapter 20
How Site Blocking Works
CONTENTS
Inside an intranet, it's easy to control the kinds of pages, information,
pictures, and other data that people are accessing. The corporation
controls what gets posted and what doesn't, and so nothing can
get posted that the company believes would be objectionable. That's
far from true out on the Internet, however. Objectionable content
makes up a very small part of what's available on the Internet,
and to find the objectionable content you have to do a bit of
digging. Still, anyone who wants to find it can certainly get
access to it.
Congress, among others, has tried to ban certain kinds of content-such
as pornography-from being available on the Internet. The real
answer to the problem, though, doesn't lie in legislation, because
even if such laws are held constitutional, anyone who truly understands
the Internet and its technology also recognizes that the laws
are unenforceable. The real answer lies with technology itself:
software that will allow people such as parents and intranet administrators
to block access to those sites. A number of companies make and
sell software that allows site blocking.
Many problems can occur if people from inside an intranet are
visiting pornographic or objectionable sites on the intranet.
And in any event, companies would not want employees viewing those
kinds of sites on company time, using company hardware, software,
and network resources.
To block objectionable sites on an intranet, the answer is not
to put site-blocking software on each individual computer on the
network. It would be too unwieldy and expensive to do that. Instead,
server-based site-blocking software is used. Site-blocking software
on a proxy server examines the URLs sent to it and decides whether
or not to retrieve the requested page by reviewing databases that
list objectionable sites and words.
One group working on the issue is PICS (Platform for Internet
Content Selection). They are trying to develop industry standards
for technology that would allow the content of all sites and documents
on the Internet to be rated according to its sexual and violent
content. They would also create standards that would allow software
to be developed that would be able to block sites based on those
ratings.
Not all intranets need site-blocking software. However, intranet
administrators may want to know what kind of sites people on the
intranet are visiting. They can use server-based software that
can keep logs of what kinds of sites people are visiting on the
Internet. This will help not only to decide whether site-blocking
software is needed, but also to know when more server resources
are needed for the intranet.
Since intranets allow access to the Internet, intranet users can
visit objectionable sites on the Internet-sites with sexual, violent,
or other kinds of distasteful content. This illustration shows
how server-based blocking software might work, based on the SurfWatch
product that can be used to block sites on individual computers.
- Site-blocking software examines the URL of every request going
out of the intranet. URLs most likely to be unacceptable will
be accessing the Web (http); newsgroups (nntp); ftp (ftp); gopher
(gopher); and Internet chat (irc). The software takes each of
those five types of URLs and puts them each in their own separate
"boxes." The rest of the intranet information going
out is allowed to go through.
- Every URL in each of the boxes is checked against a database
of the URLs of objectionable sites. If the blocking software finds
that any of the URLs are from objectionable sites, it won't allow
that information to be passed on to the intranet. Products like
SurfWatch check thousands of sites, and list several thousand
in their database that have been found to be objectionable.
- The site-blocking software next checks the URL against a database
of words (such as "sex") that may indicate that the
material being requested may be objectionable. If the blocking
software finds a matching pattern, it won't allow that information
to be passed on to the intranet.
- Site-blocking software can then use a third method of checking
for objectionable sites, a rating system called PICS (Platform
for Internet Content Selection). If site-blocking software finds,
based on the rating system, that the URL is for a site that may
contain objectionable material, it won't allow access to that
site. Rules about passing or dropping can be configured to control.
access to unrated sites.
Contact
reference@developer.com with questions or comments.
Copyright 1998
EarthWeb Inc., All rights reserved.
PLEASE READ THE ACCEPTABLE USAGE STATEMENT.
Copyright 1998 Macmillan Computer Publishing. All rights reserved.
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