Step 5: Import
Blacklist into Bad-Sites
Download the script named ImportBlacklist.vbs by clicking the 94079.zip link. Unzip
the downloaded file and copy the two files it
contains to your ISA Server's hard drive. (I'll
explain the other file, ScheduledUpdate.bat,
in a moment.)
The ImportBlacklist.vbs script imports a text
file of domain names into a domain name set
on ISA Server 2004 or 2006, either the Standard
or Enterprise edition. Copy the porn\domains
blacklist file to the folder on your ISA Server
system that contains the ImportBlacklist.vbs
script, then run the following command in a CMD shell (type the command all on one line)
to fill your Bad-Sites list:
cscript.exe ImportBlacklist.vbs
Bad-Sites domains
To import domains from multiple files,
merge them all together into one large file. For
example, to append one file (domains1) to the
end of another file (domains2), use the Type
command as follows:
type domains1 >> domains2
Alternatively, you could create multiple BadSites sets, one for each file to be imported, and
add all these Bad-Sites sets to the destination
in the Site_Blocker rule.
By default, the script deletes the contents of
the domain name set first, then imports from
the text file, so it's better to do your list management in the text file than in the domain name
set itself. When the script finishes, refresh your
ISA Server Management console to see the
new contents of the Bad-Sites list (or close and
reopen the console, which is often faster).
That's it! Now, when a user requests a
file from a blocked domain, the user will get an error page instead. As long as the HTTP
request is routed through ISA Server, this domain blocking works even when the user's
browser isn't configured as a Web proxy client. (But it's better to configure all browsers as
proxy clients.) And the performance penalty
of ongoing domain blocking is relatively small
because it's not regular expression pattern
matching, it's just simple string comparisons
against the user's requested URL. Very slick.
Step 6: Schedule Updates
Manually downloading blacklist updates and
importing them into ISA Server is easy enough,
but it can be tedious. Fortunately, it can be
scripted. A scheduled batch script that uses a
free Windows version of wget.exe (http://www.gnu.org/software/wget) can download the
latest version of your favorite blacklist every
week or night, then run gunzip.exe, tar.exe, and
ImportBlacklist.vbs to update your ISA Server
system hands-free.
Listing 1 shows a simple batch script named
ScheduledUpdate.bat that performs these
tasks. The script downloads a small demo
blacklist from URLBlacklist.com and imports
its porn list into an ISA Server domain name set
named Bad-Sites using the ImportBlacklist.vbs
script. In real life, you'll need to edit this script
to download the full blacklist for which you've
paid and to perform error-checking, logging, and/or administrator notification. Use
the Scheduled Tasks
applet in Control
Panel to schedule the
script.
Updating your
blacklist is important
because new bad sites
are found every week. Scheduling this work
is important because
of the time it takes to
import very large lists. On a server with a single 2.2GHz Pentium 4
CPU, for example, it
takes less than 10 minutes to import 100,000
domains from a blacklist file, but that same
machine requires three hours to import 500,000
domains. And during the import process, the
CPU will be pegged at 100 percent. So, schedule the blacklist updates for off-peak hours,
and run the ImportBlacklist.vbs script with the
\belownormal option (as the last line of Listing
1 shows) to use a lower multitasking priority.
Other ISA Server processes will have an easier
time getting CPU cycles.
Note that you'll have to allow ISA Server
HTTP access to the Internet for the batch
script to run. Following the procedure in Step
3, create a rule that gives ISA Server access
only to the blacklist download site. Set the
source network to Local Host and the destination URL to the location of the blacklist to be
downloaded.
Importing blacklists for domain blocking is
just one example of ISA Server's scriptability.
You can find lots of other scripts at sites such as
http://www.isatools.org, http://www.isaserver.bm, and http://www.isascripts.org (my site),
and Microsoft has an ISA Server software development kit (SDK) if you want to write your own.
Using blacklists and scripts as we've done here
won't be as scalable or full-featured as using
a commercial content filter, but if you're on a
budget, it might be good enough.
SOLUTION STEPS:
- Use ISA Server.
- Create a domain
name set.
- Create a blocking rule.
- Download a blacklist.
- Import blacklist
into Bad-Sites domain
name set.
- Schedule updates.
End of Article
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