Definition - What does Spam mean?
Spam refers to the use of electronic messaging systems to send out unrequested or unwanted messages in bulk.
The difficulty with stopping spam is that the economics of it are so compelling. While most would agree that spamming is unethical, the cost of delivering a message via spam is next to nothing. If even a tiny percentage of targets respond, a spam campaign can be successful economically.
Techopedia explains Spam
The most common form of spam is email spam, but the term also applies to any message sent electronically that is unsolicited and bulk. This includes: instant message spam, search engine spam, blog spam, Usenet newsgroup spam, wiki spam, classified ads spam, Internet forum spam, social media spam, junk fax spam, and so on.
Some experts estimated spam deliveries at nearly seven trillion in 2011. Unfortunately, spammers can be hard to catch, and the numbers will undoubtedly expand. As countries have passed laws outlawing spam, the technology and techniques have evolved. Whereas in the early 90s you'd see spam originating in the United States, most spam now originates overseas. As well, more spam is being sent not from a single location, but from botnets. This opens up the door to even greater security threats, as spam is used for malicious attacks such as phishing.