There are types of people who care about safety of their computer. Every time when they plug a USB Flash or disks, they scan it for viruses. At the same time, I've seen users who don't care about that at all.
My computer once was infected with a Trojan virus. It made me very nervous to find and delete it, because some Anti-virus softwares I tried weren't able to determine it. After that, I often update the program and perform a periodical scan of the HDD.
Have your computer ever been infected with viruses? Do you give attention to devices when you plug/ input them to the computer?