do you need to add an anti virus on mac pros

NO! Return it for a refund. If you are nervous, down load from the Internet Clamav for free. I do not use any antivirus program.

Ciao.

You can get by just fine without anti-virus at this time, though you should be aware of dangers and be cautious online. See my Mac Malware Guide.

Note that, even if you do decide to use anti-virus software, you shouldn't pay for anything. The best options are free. So return whatever software you were convinced to buy. Also, although ClamXav has been a popular recommendation on these forums, recent testing I did shows that it doesn't do such a great job. See Mac anti-virus detection rates.