Yes, mcafee is designed to automatically detect , block and remove virus, spywares, and all type of online threats. On the contrary we should pay attention while opening any unknown email attachments. and visting any non secure websites. Just go through the following link to know more on how to be cautious online.http://community.mcafee.com/docs/DOC-1121
And apart from these update the software and run frequent scans. You should be all right. Do report on a thread if you have any issues.
McAfee Online Community Moderator