build a smal webspider

Hi Freelancers, For a research project we need some software: It needs to spider the web for websites with specific domain (.com, .de, .es, etc) It should search for the file '[login to view URL]' on those website and look for a specific line in that file (we want to be able to change this line) When the spider finds this specific line, it should add the url of the website to a database and start searching further on the web within the domain. if possible it shpuld run on a linux, wit php, etc. we are not going to use it for spamming, hacking, etc: this is only a research project!) Lucas