How do you ban a person from sim, no matter which alt they use?

[GreySchoolofWizardry]

I seem to remember that IP banning is not allowed. However, I know that some sims have security that prevent a person from coming back on an alternate account. Is there an allowable way in which I can prevent a person from coming back to our sim, no matter which account they use?

I'm aware that I can close the sim to the public, and have it be group only. I don't want to do that. 

[Alwin Alcott]

yes there is, lock it for everyone except you, or your personal group.

All other methods have their weak spots.

For example... a ip ban won't work when using a VPN

and so on...

[Amethyst Jetaime]

The problem with an IP ban is that people sometimes share the same IP address.  For example people that work at the same place, or that live in a dorm.  Even some apt. complexes share the same IP address.  So you can never be sure that you are IP banning the right person and can easily ban people that are innocent and that you may want to come to your sim.

Most people that use IP bans are just ignorant of these facts and are only hurting theirselves in the long run.

[lapandamonica]

quiero una casa:heart::matte-motes-crying::matte-motes-not-even:

[Lindal Kidd]

Only Linden Lab can issue an IP ban.

Some residents use an "alt detector" to determine if a new visitor has the same IP as someone on their ban list.  If they find a match, they ban them as an alt.

But there is a problem with these devices.  They can produce a false positive (Amethyst's example of a dorm or apartment sharing an IP address), or a false negative (Alwin's example of someone using a VPN to mask their IP address.)  Besides the fact that they often give wrong information, SHARING that information with anyone is against the Terms of Service; it's regarded as revealing personal information.  For example, it's OK for me to know that Bruce and Judy share an IP address.  It is NOT OK for me to tell other people, "Oh, Bruce is Judy's alt, they have the same IP."

Your best approach is to ban individuals one at a time, based on their behavior.  Submit Abuse Reports too, if that seems indicated.  If you suspect someone is an alt, reference your previous ARs.