unknown workgroup computer

I have a wireless home network with 4 PCs and a 5th PC has
appeared on my network although I did not add it. Has
somebody gained access to my network and compromised the
security? How do I get rid of it?

It is possible that someone is hijacking your network ( using your wireless
bandwidth ). What kind of security do you have set up on your wireless
network? Many Access Points allow you to only allow certain MAC addresses
onto the network. This is a small piece of the security you should have
enabled. Other items are 802.1x security, WEP keys, and WPA. Look into
what your Access Point supports by going to their web site or read the
manual. You should lock down the AP as much as possible, and set your
wireless devices to only talk with the AP.

--
--
Dusty Harper
Microsoft Corporation
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This posting is provided "AS IS", with NO warranties and confers NO rights
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"tjo" <juicefreak@yahoo.com> wrote in message
news:1a28301c41d94$afaecb90$a501280a@phx.gbl...
> I have a wireless home network with 4 PCs and a 5th PC has
> appeared on my network although I did not add it. Has
> somebody gained access to my network and compromised the
> security? How do I get rid of it?

On Thu, 8 Apr 2004 11:09:51 -0700, "tjo" <*email_address_deleted*> wrote:

>I have a wireless home network with 4 PCs and a 5th PC has
>appeared on my network although I did not add it. Has
>somebody gained access to my network and compromised the
>security? How do I get rid of it?

Enable WEP / WPA. Use non-trivial values for each. (No "My dog has fleas").
Enable MAC filtering.
Disable DHCP, and assign an address to each computer manually.
Change the subnet of your LAN - don't use the default.
Change the router management password, and disable remote (WAN) management.
Don't disable SSID broadcast - some configurations require the SSID broadcast.
But change the SSID itself - to something that doesn't identify you, or the
equipment.
Enable the router activity log. Examine it regularly. Know what each
connection listed represents - you? a neighbor?.
Install a software firewall on every computer connected to a wireless LAN. Put
manually assigned ip addresses in the Local (highly trusted) Zone. Open the
following ports for file sharing only in the Local Zone: TCP 139, 445; UDP 137,
138, 445.
Use non-trivial userids and passwords on every computer connected to a wireless
LAN. Disable or delete Administrator and Guest userids.
Stay educated - know what the threats are. Newsgroups alt.internet.wireless and
microsoft.public.windows.networking,wireless are good places to start.

And please don't contribute to the spread of email address mining viruses.
Learn to munge your email address properly, to keep yourself a bit safer when
posting to open forums. Protect yourself and the rest of the internet - never
post your address unmunged.
http://www.mailmsg.com/SPAM_munging.htm

Cheers,
Chuck
Paranoia comes from experience - and is not necessarily a bad thing.