For the past two months, my hard drive has been making a number of strange sounds. I can't determine a specific pattern of when they occur. When they do, I close every possible task/program on my PC, but they don't stop.
I've checked my antivirus (Avast) but it was not scanning at that moment. Turning it off didn't help. The only thing that stops the sounds is disabling the Internet. This makes me paranoid that someone's connecting to my PC and crawling my hard drive.
The series of sounds consists of (by "scratch" I'll mean the normal hard drive sounds): four identical scratch sounds follow by one end up scratch with different sound. The whole pack of sounds is repeated every two or three seconds. If I disable Internet access, the sounds stop, and if I remain disconnected for a little while, when I get on the Internet again, the sounds disappear.
As I'm writing this, there are no sounds. Sometimes they disappear for a whole day.
I've performed some scans with online tools, but discovered nothing. I have pretty good "online hygiene"; I don't open stupid links or downloading funny