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.