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i downloaded ubuntu today and can't open avast or zonealarm

While it's laudable that you're making an effort to protect yourself (and therefore us) you should know there's no "ZoneAlarm for Linux". Tuxguardian, Leopardflower, Fireflier and Pgrd were examples of "ZoneAlarm-for-Linux"-like applications but none of them are maintained any more. If you want to use an antivirus application other than ClamAV you best download it from the vendors own website.

*It could also be you really wanted to ask "What do I need to do to keep my Linux installation safe?". In that case, because while viruses do not affect Linux, you best start reading your distributions basic user documentation (and maybe "rute user's tutorial and exposition") and its admin / security documentation after which you'll be able to ask more specific questions.

Linux has firewall capability built into the kernel; it's called iptables. Linux "firewall" programs are frontends for configuring iptables.

Here's what Ubuntu says about its included frontend, ufw, which is a command line program.
https://help.ubuntu.com/12.10/serverguide/firewall.html

If you would like an easy-to-use GUI frontend for your firewall, open the Ubuntu Software Center and install gufw; it's in the Ubuntu software repositories ("repos" for short).

As regards anti-virus, many Linux users choose not to run one, as there are no Linux viruses in the wild (there is "social engineering" malware--be careful what you click). I am an exception; I use AVG for Linux.

Here's an article about AV for Linux: http://www.makeuseof.com/tag/free-li...irus-programs/