I've got a very popular site that is making me money. But over the past few months, I've noticed an increase in hack attempts. I log all unusual attempts so I can see what's going on. I've noticed that all these hack attempts come from users with blank user agents. I'm thinking about just banning anyone with a blank user agent string. But will I be banning valid users? Can anyone tell me if there are valid visitors out there with a blank user agent string?