If you have been unfortunate enough to have malware on your Mac, then you most likely installed it through a fake Adobe Flash Updater. This spoof is the number one way that Macs can get compromised. The type of malware varies greatly, but the danger is the same, so it's important to know how to avoid it.
First, go to System Preferences -> Adobe Flash and choose the Updates tab. It defaults to the choice to let Adobe install updates. You can also check for updates here or move to a manual mode. Either way this is the place where you either want to check for updates or install an update.
So, do you need Flash at all? Well, it depends. I do not have Adobe Flash installed on my Mac and I have no problem accessing content from websites. But depending on which ones you frequent, you may need to have it on your machine.