Disk space attacks are a form of resource utilization attacks resulting in denial of service. Disk space if a finite resource in the computers. If it is fully utilized, systems would fail in further processing the computing requests. The options available are to remove some of the existing data or add new disk space.
It is difficult to add new disk space if you do not have a enterprise class server with hot pluggable disk arrays. Removing files are not very easy if you do not know which are to be deleted and which files need to be kept
One of the countermeasure mechanism is to have some large files kept in a pre-planned folder in your computer. If it is your personal computer, keep some movies, music etc. so that the you have some utilization of the disk space at the same time it can used as the counter measure for the disk space attacks.
Reserving some considerable space for such attacks would help you delete this folder / file and release some space for computing. This gives a breathing space for you to do the analysis and mitigation for the real problems