Stop robots from subscribing
For the last 3 days I'm having about 20 new subscribers per hour, all coming from some kind of robot, names are something like 5909f4d180047. I use a double-opt-in list so they're unconfirmed and the only problem is that it's cluttering my subscribers' database.
Is there an easy way to avoid this? I'm using the list's subscribing form, could I add a "tick if you're human" ticking box or something similar to it?
Many thanks in advance