Spam Types 1. Advertising spam

This type of messages are obviously built with the purpose of selling a service/product or to announce the availability of services/products.

2. Fishing (aka phishing) spam

This type of messages represents a real threat to the personal/banking information of the user that receives it. These messages are built in a way to impersonate legitimate messages that ask for personal information. It is easy to defend against this type of messages since no Internet or real world customer service asks for personal information; and certainly, if they ever lose it or need to update it, they will not use the electronic way of contacting their customer for such information.

3. Scam spam

Although it makes a nice rhyme, this type of spam is also dangerous since it is built to determine the user to pay some money or offer contact information in the perspective of earning a certain (large) sum of money. Many pyramidal system scams are made by means of spam messages. Nigerian letter scams are also performed through this type of messages. In this category can also be entered the fake/replica type of messages that are similar to advertising ones except they are meant to trick the user in buying a low grade product or a product that resembles an expensive product (ex.: watches) for a larger sum of money than the product is actually worth.

4. Virus/Trojan spam

This type of messages are, in most cases, sent by worm/virus infected machines that try to spread the infection to other vulnerable systems, by tricking the user to read the infected message or by exploiting a security vulnerability.

Trojan virus spam is a variant of the Virus spam; this type of message offers the user an application for free (in some cases the user is tricked to believe the application may be very valuable and that, in other conditions, it would cost a large sum of money), that application can be itself harmful or deliberately infect the computer system with harmful applications, that range from collecting personal information found stored in the system, collect access credentials, use the computer system as a base location for infecting other network connected systems to rendering the system unusable. The message is often about a Spam filtering or removing application, since you will be more compelled to run such an application, the only thing that can start the infection process.

5. Data mining spam

A valuable piece of information for spammers is also represented by the accuracy of the information they have about you, besides the actual e-mail address. Many spammers buy e-mail addresses databases from other spammers which, in turn, they use to drive their campaigns. A large database with expired or no longer valid addresses is useless, so spammers use many tricks to reveal more information about you. One often used trick is to include un-subscribe or opt-out mechanisms and instructions; this way, spammers validate the database (in many cases automatically, since you perform all the required operations) and consolidate the valid and still reachable mailboxes from the ones that no longer function. This way, they achieve two goals: sending the messages and consolidating the e-mail addresses database.