I have recently been getting spam in my inbox that is also automatically adding itself to my contact list.  I don't understand how this can happen.  With  most I just go to my contact list and delete them.  However some of the spam has no identifiable e-mail addy just a very long string of indecipherable letters that don not show up in my contact list.  Is there a way to prevent this adding to contact list from happening?

Also, in my contact list  there are 5 red boxes with 1 random letter let in each of them.  What are they and why don't they have the checkmark box on the left so I can delete them?  Are the connected in some way to my first problem?

In advance, I would like to say TYVM for  any assistance provided.