Spam problem in comments
For beginning let’s understand why spam in comments is actually bad. Two principal causes are possible.

Spam causes notable inconveniences to your readers. When visitors see a considerable quantity of advertising dust among messages, they can have negative impressions: this resource is thrown, it does not represent interest even for the owner. The blog with a considerable quantity of spams-comments is in most cases seems as not trustable.

Search optimization.
It is possible to assume that spams-comments reduce relevance of a resource for search systems. If the site is devoted service of cars, but the considerable part of comments contains advertising of pharmaceutical preparations the subjects of automobile site will be washed a little away.

Methods of struggle against a spam in comments
Today experts have developed set of methods of struggle against a spam, but the guaranteed way is not present. Struggle against a spam reminds race of the weapon and protection frames from it. We will consider widespread methods of protection against a spam.



Registration of commentators and comments moderations.
Perhaps, it is one of the most effective methods. Its essence consists that all users can not add comments , but only registered users can. Registration of commentators is a barrier to a mass spam sending. Comments moderation is an opinions allowed visitors publish their comment only after directly approving by the manager of an Internet resource. In most cases control systems of the site maintenance provides possibility to resolve the publication of comments only from “the entrusted” commentators — at whom at least one comment earlier has been approved. System pluses: high enough level of protection against a spam. Minuses: the manager of a site will need to pay attention to checking at users, to cleaning from time to time an inactive part of the users. Besides, there are inconveniences for visitors — not everyone will want to register to leave the opinion on published article, or to wait for comment approval.

Use of identification services.
This method closely adjoins to previous described and is similar to identification system of Microsoft (Passport)and Google (Google Account). Users of the listed companies are registered only once, and then use the same login and the password for access to all services given by the company (for example if you are registered in Gmail, with the same data you can enter in Google Calendar, etc. services). There is a lot of such services. The most known is TypeKey. If the visitor is registered in TypeKey, he can leave comments on all sites supporting this service.