Not ticking any boxes means no targets are allowed. Ticking all boxes includes all targets, such as corpses, trees, buildings, invlunerable units, and others.
For just unit targets, I recommend just ticking the "Vulnerable" box (and invulnerable as well, if you want them to be included), or "Friendly" and "Enemy" boxes.
Finally finding about some of the bots that are flooding the users online - bytespider apparently is a huge offender here - ignores robots.txt and comes in from a ton of different IPs
Ghan has said he has fixed this. Monovertex please confirm this fix. This was only a problem with people that had signatures in the upper levels like not the special members but the respected members.