Spam Comments are mostly for promotions or for backlinks.

Consider these things and hopefully you can get help.

In Wordpress , you can install and activate plugin like akmiest or anti spam they will help you do the job.

But what if you do not want to install any plugin or your website/blog platform does not support that?

What you will do is that whenever you are going to approve any comment on your blog or website, always check these things before you approve or delete any post comment.
Name: One of the important thing in comment is that you can easily identify spammers and real user if you can use your brain.

Do not approve comments with names like
companies,keywords or others.
Mostly, spammers comment using keywords as name because they want links and rank that particular keywords.

Email: Well i hope you know what is email and
what name real people use in creating an email.

So do not approve comments with emails
likedddfhjh.bla bla. .com.

Comments: Now here is the real part comment. If the name and email is ok then you have to be more extra careful while going through the user comment because i have noticed that most of new bloggers approve comments without checking all this things.

One of the big mistake which you must not make is by not reading comments carefully sometimes they link someparticular keyword with links. Sometimes they appreciate you
and in end they put regards and link.
Most times we approve them and think how nice they are but all they want is to attach their link to your blog.

Also endeavour to read their comments so as to know what they are talking like sometimes you will read hi i am his name, i like to invite you in our promotional posts see google for this.

Be careful and do not accept these type of
comments instead delete them because they are spam comments and might be harmful to your blog or website.

I hope this will help you in spam comments
moderation.

Good luck.

Source: http://www.johntechservice.com.ng/2017/03/stop-spam-comments-blogger-wordpres.html?m=1

good post!