ClassiPress itself has an option where you can "Enable reCaptcha" on new registrations which can help, as well as actually moderating ads before they are published to ensure they are not just spam listings. As for actually knowing if someone is a scammer though, this is not necessarily something you can determine just by a registration. Outside of this, there may also be other plugins and mods out there which you can use to protect your site further, such as some steps you can take/plugins which can block certain known spam-source countries/IPs from accessing your site. AppThemes does not officially support third party plugins so we cannot guarantee that all plugins will definitely be compatible with our themes, so specific recommendations can be difficult. Thanks.
