My server at 4webspace was brought down tonight by a DOS attack.

Can anyone explain exactly what this is ?

DOS stands for Denial of Service.

There are many different ways this can be done but for the most part and most common method it is a concentrated attack on a single server and or network.

Check out http://www.denialinfo.com/ for a few good resouces on DOS attacks and what to do about them.

Regards,

Mike