First, the noise you're hearing might be perfectly normal.. Fans kick in when the workload of a computer goes up.
Let us know more about your computer.. Laptop or desktop? Let us know which operating system you've got and whether you have a firewall installed on your computer. Your wireless router/modem should have a firewall or at least NAT.. Open the router/modem settings and enable the firewall.
Next, open up the case of the computer and use compressed air to blow out all the dust around the processor, heatsink, and all fans.
Next, secure the wireless network connection. A WPA/WPA2 passphrase is a must..
Next, if you're using Windows 2000/XP/Vista, download, install, update, then run a full system scan with the free antispyware program from the link below. Delete anything it finds.:
Ewido/AVG Antispyware 7.5 Tool
Hope this helps and let us know more.
I have a good computer 512 MB RAM, no problems with it when I am offline. I got a wireless internet connection, one, which is not secure. Since then, nearly every time when I am on the internet, after 5 minutes or so the computer starts making loud noise, probably from the fan and the CPU usage shows high. When I disconnect, the noise stops. Then I can connect again and have 5 minutes to work online. It is not always 5 minutes, sometimes it is much longer, but mostly about 5 min. I installed AVG antivirus software, but it did not help. Someone told me this could be caused by someone using the capacity of my computer when I am online. Would there be some program on my computer that would facilitate this? How would I find it, is there some software I could use, that would help, even though the paid version of AVG did not help? Thank you very much!