I think malware is a significant threat because the mitigation, like antivirus software, hasn't evolved to a point to really mitigate the risk to a reasonable degree.

You can never protect yourself 100%. What you do is protect yourself as much as possible and mitigate risk to an acceptable degree. You can never remove all risk.

I think a cyber-terrorism attack is overblown, though the threat exists. I think al Qaeda and other groups are more interested in symbolic terrorism, like what they did to the World Trade Center - suicide bombers or something that really has an effect and is meaningful to people.

Are hackers a threat? The degree of threat presented by any conduct, whether legal or illegal, depends on the actions and intent of the individual and the harm they cause.

For the average home-user, anti-virus software is a must.

I think it goes back to my high school days. In computer class, the first assignment was to write a program to print the first 100 Fibonacci numbers. Instead, I wrote a program that would steal passwords of students. My teacher gave me an A.