The internet is a nasty place sometimes and there are folks out there who want to do nothing but waste your time and valuable site space with their spam listings.
Here are some ways you can combat spam with your WordPress site in general and Business Directory Plugin in particular:
General WordPress Suggestions
- Make sure you use plugins like Akismet to cut down spam comments
- Use spam registration prevention plugins, like Stop Spammers Plugin (more about the settings and use here: http://www.wpbeginner.com/plug.....ship-site/)
- Track the spammers for a bit and see if there's a pattern, like they all come from the same country. If so, use an IP blocker to kill all traffic from that country if it's irrelevant to your site. Plugins like LionScripts IP Blocker can help here
Specific BD suggestions to combat spam
- Turn on Registration for listings (free listings attract more spam than registered ones)
- Make sure you use reCAPTCHA integration, as this helps cut down on bot (automatic) spam
- Require admin approval for your listings to avoid spammers getting through without you moderating them