What is spam?
While the most widely recognized form of spam is email spam, the term is applied to similar abuses in other media: social networking sites, Usenet newsgroups, search engines, comments on blogs and news articles, text messages, or Internet forums.
How spam works
Spamming remains economically viable because spammers have no operating costs beyond the management of their mailing lists, servers and other infrastructures, and it is difficult to hold senders accountable for their mass mailings. The costs are borne by victims and by Internet service providers, and include lost productivity, fraud, bandwidth and email server saturation, malware proliferation, storage capacity reduction, etc.
Most common types of spam
Spam can be classified into different categories according to the topic used:
Inappropriate contents, pornography in particular, have been widely exploited by cybercriminals. Additionally, as online dating sites have grown in popularity, spammers have increasingly used messages related to fake user registration websites designed to trick users into giving up personal data.
Users' security concerns are also frequently used as bait in spam campaigns, with spammers offering antivirus and anti-spam programs, storage services, website optimization services, etc., which are actually used to bypass defense systems.
Over the years, financially-themed spam - with supposed methods for making money fast, financial offers or grants - has become frequent. This type of spam also entices users to get real estate loans, make investments, or buy goods and services on credit. These messages are often used as bait in scams: emails encouraging the victim to invest in overseas companies, chain letters, pyramidal scams, fake requests for help, etc. Contests and sweepstakes offering users the opportunity to win lots of money easily are also popular.
Health-related spam usually offers miracle products, almost always fake or not approved, or marketed via illegal channels. Falsified popular drugs, alternative medicine treatments, and miracle health and weight-loss products are among the most widely used. Other topics such as religion or mental disorders are also used as bait.
As for education/training-themed messages, spammers commonly send fake offers for short-term and long-term training courses, scholarships and seminars, sometimes impersonating well-known educational institutions while others making up the name of a bogus institution.
Many hackers don't hesitate to use all types of ruses to redirect users to other sites. Thus, they may use spam messages to lure victims to websites designed to manipulate them into giving up personal data or downloading malware.
Additionally, they use spam messages to collect users' email addresses and integrate them into botnets. In this regard, many spam variants take advantage of user networks by infecting a user, and then forwarding the message containing the virus to all contacts in the victim's address book in order to spread to as many systems as possible.