Sotos wrote: Let's say I enter range of IP's for Cyprus and Greece only
Wouldn't that exclude all Cyprus websites that are hosted abroad?
Web Crawler has many options for spidering the web. Range of IP's, unique IP's, list of sites, ftp servers, secure servers etc. Also, indexing file type (txt, htm, html, php, asp, pdf, swf etc. You can select one or all the options.
So it wouldn't. This sites will be on the list to spider.
Additionally, settings for spam pages, gateway pages, scripts designed to cheat Crawler etc. Crawler can recognize spam, and knows what to do with found spam page (black lists of IP's, whole web servers, web sites...). Crawler is the mind of engine. He reads how many times you repeated keyword within the size of text, is your text the same color as page background, link loops etc.
Finally, SE Server is not updated so often. On the other hand, Crawler is being updated very often. Like Anti virus software.