Setting a script to automatically download a file from nai.com ftp site?

Hello, I want to be able to download my anti-virus weekly update files in the middle of the night through the use of a script and ftping??? I want to connect to ftp.nai.com and download the sdat weekly anti-virus update. Is this possible and if so can anybody point me in the right direction. Thanx in advance Damian Buckley