Spam - my forum is flooded with spam, what can I do

SMF by default offers three tools to help you keeping spammers out of your forum:
 * 1) account activation - admins can decide to either ask their new members to visit an activation link sent to the newly registered member by email or to put all the newly registered members in the approval queue and then personally activate only the non-spammer accounts;
 * 2) the captcha - admins can set a verification code (called also captcha) that users have to decipher in order to be able to proceed with the registration;
 * 3) verification questions - admins can introduce a certain number of custom question and answer, then users that are registering have to answer those questions in order to proceed with the registration.

The first measure is available at admin > Members > Registration > Settings. The second and the third can be configured in admin > Configuration > Security and Moderation > Anti-Spam.

The level of complexity of the verification code can be set from none (no verification code displayed) to extreme (the letters are extremely distorted and it should be very difficult to decipher for the bots). Just below box with the settings for the verification code, there is the box used to configure the verification questions. Usually this is the most efficient anti-spam method provided by the default SMF. A couple of things to note about this method: From the admin panel it's possible to set as many questions you want, and also the number of questions that each user will be asked to fill during the registration (this number mush be inserted in the field Number of verification questions user must answer that is directly below the captcha example). If you configure 10 questions and then you set to show 2 in the registration page, SMF will show two random questions from the 10 configured each time a new member tries to register).
 * bots are usually quite good at math, so you should avoit questions like: what's the result of 2+2? and alike.
 * if you expect to have an international audience (with people that speak many different languages) it could be not a good option use questions because the person registering maybe doesn't know very well the language of the question.

But that's not all! Of course one of the most important SMF feature are mods, and at the mod site there is an entire category of Spam Prevention mods. At the moment the most effective anti-spam mods reported by our community are (in alphabetical order):
 * Bad Behavior
 * Forum Firewall
 * httpBL
 * Stop Forum Spam
 * Stop Spammer