slow browsers on imac and macbook

Simultaneously our imac and macbook both started acting weird, at the same time. We were gone for 2 weeks and had a house sitter who had access to our wireless network as well as a guest account to our imac. When we came back I noticed that surfing the web was extremely slow. At times google would even time out while performing basic searches. When I run speed tests on the CNET bandwidth meter online test, the line speed comes up around 2362 compared with my work macbook on the same wireless network clocking 4656. The imac is as slow, if not slower. I've run ClamXav on the imac and it quarantined a couple of files, but since (rebooting) I haven't noticed any improvement. What could it be?

Check your router stats and reset your wireless access code.

Where would I find the router log if I'm using the apple airport base station? I just reset the wireless access code, so we'll see if that helps. Thanks

The router stats are in the air port utility. What you would be looking for is what devices (computers, DNLA, wireless) are connecting to your network. If there are devices connected that you do not recognize, chances are that others are using your internet connection. You may need to identify each of these by their MAC address.

Thanks Betavirus. I can see their MAC addresses and am checking them one by one. Some devices are labeled and make it easy to tell which ones are mine. If there's one on there that isn't mine, is there anything I can do to kick them off? I reset the wireless passwords.

Incidentally the speed of my Google Chrome browser when performing simple search tasks still didn't improve, the CNET bandwidth meter test seems better, but the weird part is when I disconnect the ethernet cable from the back of my imac Chrome seemed to become faster when performing searches. Now I'm totally confused.

If you can't identify the MAC address and you are sure it is not one of your devices then someone is using your bandwidth. If you changed the wifi password it would eliminate anyone who does not know the new one unless they are finding it by logging into your router remotely.

Sometimes just a power-down and re-start of the router will improve speed issues. As a security measure I set all of my devices with fixed IP's in an obscure range (like 192.168.1.181 to 192.168.1.192) and disable DHCP.