How do you know for sher that a file you download dose not have a virus,trojan rootkit ect in it?

i use avast,spybot search and destroy ,a-squared and avg anti-root kit is theis good if a scan my system after i download a program and they find nothing dose it mean the file is virus / hacker tool safe . so know one can hack me

How do you know for sher that a file you download dose not have a virus,trojan rootkit ect in it?matchless

It is almost as simple as knowing your source.

If it is a file you got via Yahoo Mail - Yahoo scans it with Norton first before it lets you download the attachment, so you get that extra layer of scanning there.

If you are downloading from a website - one trick is to use FIREFOX (http://www.mozilla.com/en-US/firefox/) and get the McAfee SiteAdvisor add-on for Firefox (http://siteadvisor.com/) and then if you don't see "green" down in the Firefox status bar don't download from that site - go somewhere else. (Why anyone would use IE when there is Firefox is beyond me.)

Also, some sites like Download.com, owned by c|net, offer "safe, trusted, and spyware-free" files for download - games, software, music, et cetera, some for free and some for money.