Security when connecting to cable modem via USB

[kevin66]

I've been asked to diagnose some performance problems with a neighbour's 6-7 year old PC which is connected to an NTL cable modem via USB. This is not a setup I've used myself at home as I use ethernet cabling with a router between the cable modem and PC. I'm well aware of the security risks of connecting a PC directly to a cable model via ethernet. Do those same risks apply when the connection is via USB instead, or is USB a little more secure?

[brundles]

If the PC is running slowly then swap to an ethernet connected router - TW were doing an offer of a free wireless router to new and existing customers although I think it's on hold at the moment because of issues with the firmware interface and IE7.

The USB connected modem will still suffer from the same security problems as a direct ethernet connection - the PC is still presented with the same network packets as the end result.

From a performance perspective there are two things:
1. USB uses much more CPU overhead than a direct ethernet stream.
2. Assuming the PC does have a firewall that is going to have to do a lot more work with all of the extra junk received at the modem, again chewing up CPU time. Getting a router removes that workload.

This won't fix all of your problems, but it's a start.

If all yoru doing is running some tests just use windows firewall.If you suspect a virus/trogen then id advise no net connection untill all scans are done and machine is clean before allowing on the net as outbound traffic could be abused.If your testing the machine just plug it into your router (if it has a nic of course) after said scans are run.
What is wrong with the pc btw

[kevin66]

Thanks for the feedback. This confirmed what I'd thought about the security risk.

The neighbour only really uses the PC for email and word processing. My neighbour was complaining that the box was freezing from time to time.

She had a problem a couple of weeks ago with an email that contained an attachment with a virus. Rebuilding the box at the time sorted the performance problems at the time. I'd installed AVG, Spybot and Ad-Aware at the time, though not a firewall. The PC is running Windows ME so using Windows firewall isn't an option. I may consider installing a Linux desktop this time if another rebuild is required

I wasn't aware of the extra CPU load incurred by the USB 'NIC', though this makes sense and is likely to be contributing to the performance issues given the limited spec of the box.

As it happens I've a spare router (Netgear RP114) and network card so I'll consider setting this up.

Thanks again.

[jaycee]

A USB connection to the modem is effectively a network card that plugs into a USB port. As far as the PC is concerned its the same thing, so the same precautions apply.

USB does typically use more CPU power than PCI Ethernet cards do. As these cards are very cheap (an RTL8139 based one will do) why not get her one and shove it in the PC?

If what you want is to stop her getting viruses, stop her using IE and Outlook. Firefox and Thunderbird are probably the best solutions here. AVG will check all e-mails that Thunderbird recieves thus greatly reducing the risk of infection.