You should be able to pull a list of all the systems connected by IP address on the network, and computer name.  Should give you an option around there to specify which systems can connect to the network.  This would include hard wired.  Sorry I don't have that specific router to give better details, but should work fine.  I do it with my Linksys all the time.

Specifically, you want want to block Port 80 traffic on a range of systems with the subnet, or better yet, get a second router and connect those systems you want to block and coonect them to the second router and block port 80 traffic to that router.

If this is a small number of machines, it might just be easier to give everyobbe static addressing within the LAN and then block specific machines.

You can filter access by MAC address.  If it's not listed, then no connection.

The problem is, we don't own or have access to the systems we want to block...

The static IP address sounds good, and I actually know how to do that....

If I did set up static IP's for the machines allowed, what would happen if an outside machine plugged in to the router? If they are set to automatically obtain an IP address, would they still get in? Or if the router is set to manual, would it not allow them access?

My Linksys wired router allows me to "Filer Port Range" to a series of IP Address and also to MAC addresses and this thing is about 4 years old now.  Look in the Security setup section of your router.

That keeps out even if wired connection?

And, how would I do that? Should there be some router setting to plug the machine in and grant access to each MAC address?

Thanks.

Yes it will keep out both.  Every device has a MAC address.

At a given system, find the MAC address in

Start | Run "cmd"

IPCONFIG /ALL

with the optional >My.txt (to save text which results). It is listed as something like "hardware address" and shows in pairs of characters, like 8

Try "Physical Address".

Got the MAC  addresses, and have protected the wireless at home (had WEP, now added MAC addresses as well - two layers is better than one, right?)

Anyone, the question was more for my wife's work, and.... That DSL modem / router combination does not seem to have MAC filtering.... I just rechecked (for like the third time) the manual... The only mention of a MAC address in there is how to get that modem / router's MAC address....

Thanks, though, for your time....

By the way, my router at home, (Linksys WRT54G, Firmware 4.20.7) seems to only have wireless MAC address filtering... Or (and just as likely) I'm really lacking the knowledge to know what's going on....

See if you can upgrade from WEP to WPA.