One of the most dangerous tools available to everyone’s email. In particular, the fact that an attacker can send massive groups of people the same dangerous email.
Inside a spam email, code can be laced in to attachments or the email itself. For example, an attacker can lace a virus into a PDF file that can take control of your computer (If you do not believe me, Watch This.) To protect yourself, only open emails which you are sure of the source of. If you don’t know who is sending you something or why they are sending it, ask them. Don’t go opening files which you are not sure about the source of.