[glapher]

Had to reinstall my os x on my air via the pen drive (went very smoothly, was very impressed btw) after a weird thing happened, see if anyone can shed some light.

All of a sudden with no apparent intervention or tweaking by me, my hd starts showing low space, I keep deleting and deleting (and getting system force shutdown prompts) and at one point I realise that as soon as I start up os x, and do a get info on the hd it starts incrementally decreasing the stated available space...quite strange, and I did quite a few restarts, it's not as if it might have been some background process....

I can post the console logs too.

[besson3c]

What was probably happening was an application leaking memory and consuming virtual memory, which consumes disk space in gobs. You can tell that this is the case if you can find the right app or process to quit/kill you get that disk space back, or a restart reclaims that disk space.

My bet is this is what you experienced, which is not uncommon.

[glapher]

hmmm, not a runaway log file? I had rebooted several times and I was only running finder and carbon copy cloner to get an image of the ssd, and the hd went from 40gb free space to nothing in about half an hour, nothing running almost, except maybe some daemon I am not aware of starting up with the os.

strange, anyway you cut it.

[besson3c]

It could be a runaway log file too, you can check your log folder to see if there are any large files.

In your original list and with some additions, a trojan would be the very last thing on my list of suspected culprits.