You wouldn't
think of leaving your office for the night without setting the
security alarm and making sure all the doors are locked. But
when it comes to your company's computer network, you might be
leaving it wide open to thieves. The solution? Install a
firewall.
A firewall is
nothing more or less than a gatekeeper—software that insulates
your company's computers from outside intrusion via the Net.
Firewalls work most of the time, but not always. Nonetheless,
you need firewall protection—for your network and your
individual or home PC.
Data on the
Internet travels in packets: A computer sending data over the
Net is responsible for breaking the data into small packets and
wrapping them in electronic delivery envelopes; the receiving
computer opens the packets and reassembles the contents into the
original data stream. Firewalls look at the envelopes
surrounding the packets—a fast but permissive approach. They
also look inside some of the packets to analyze the contents—a
slow but thorough task. Firewalls balance the equation by
examining the contents of the first few packets in a stream and,
if there appear to be no irregularities, taking just a cursory
glance at most of the rest of the packets as they pass by.
Just about every
computer connected to the Internet is probed methodically many
times every day; hackers make a game out of poking into randomly
selected PCs, just to see what they can find. Automatic
port-scanning software can probe hundreds of thousands of
computers in an hour, reporting back on each individual
computer's vulnerabilities. Dozens of port scanners are
available at any major software download site—many are also
free. While there are legitimate uses for port
scanners—network administrators use them to analyze their
servers—an alarming number of them are used to crack systems.
Even if hackers don't do any damage, the fact that they can
discover your server's weaknesses in seconds should send you
running for cover.
Which firewall is
best for you? Protect your network with CommandView Firewall
from Elron (NT version starts at $1,495; www.elronsw.com).
Of all the firewalls we've tested, CommandView reigns supreme
thanks to its straight forward interface and high level of
sophistication. Two others that work well for companies with
larger networks are Computer Associates eTrust Intrusion
Detection System (formerly SessionWall-3; www.sessionwall.com),
which starts at $1,945, and Check Point Software Technologies
Firewall-1 (www.
checkpoint.com), which starts at $7,995 for 100 users.
If your network
is Windows-based, chances are good you've enabled File and
Printer Sharing. But did you know that the default installation
of Windows shares printers and files across the Internet too?
That makes it trivially simple for an intruder to crack your
company's network: With no firewall in place, your passwords are
the only thing keeping the content on your system out of
prowlers' clutches. And passwords can be cracked with any of
hundreds of free tools.
The best way to
protect your business is to install a firewall immediately, but
you can also patch the hole manually. Before you make the fix in
Windows 95 or 98, check with your system administrator to make
sure the change won't conflict with any settings specific to
your company. From the Start menu, choose Settings, Control
Panel, then Network. On the Configuration tab, make sure you
have NetBEUI installed (if not, click the Add button to install
it).
If you're using a
dial-up modem, double-click on the Dial-Up Adapter and make sure
it's bound to NetBEUI and TCP/IP, but nothing else. For a DSL or
cable modem, double-click on its adapter and check for the same
things. Then double-click on each TCP/IP binding (for example,
TCP/IP -> Dial-Up Adapter), select the Bindings tab, and
uncheck all of the boxes (in particular those labeled Client for
Microsoft Networks and File and Printer Sharing for Microsoft
Networks). Finally, double-click on one NetBEUI binding (for
example, NetBEUI -> Dial-Up Adapter), and make sure all of
the boxes on the Bindings tab are checked.
For more details
on this process—or to fix the problem in Windows NT—check
out security ace Steve Gibson's detailed instructions, which
begin at grc.com/su-fixit.htm.
Solution:
Boost Your Firewall
1. Immediately after you install a network
firewall, check the manufacturer's Web site for updates.
Download and install them before you assume your network
is secure.
2. Most firewalls contain a log in the admin
utility that warns you about attempted break-ins. Leave
the warning beep on for a day or two—just to drive
home that someone is randomly trying to get into your
system on a regular basis.
3. When you do disable the warning sound, be sure
to keep the log active. This will help you track down
the culprit if you're attacked.
4. To keep your security airtight, cycle the log
files, back them up, and most of all don't allow anyone
to overwrite them. |
