Spam is unwanted mail that usually contains advertisement and is sent as bulk mail.

Find below some very typical spam features:

- in most cases sender’s e-mail address is unknown to user and turns out to be fake
- spam messages usually do not contain return e-mail address
- message subject always attracts attention
- message content is obviously of advertisement nature: web-sites advertisement, making money on the Internet methods, real estate sales ads or list of some products at special prices.

Despite of the fact that this type of spyware is usually transmitted via e-mail there are some special terms used for different versions of spam in relation to its distribution channels:

- Spam – bulk mailing.
- Spim - messages mailing via popular connections services like MSN Messenger, Yahoo Messenger.
- Spit – spam sent via IP telephony. IP telephony uses Internet for making calls.
- SMS Spam – spam sent to cell phones with the help of short messages service systems.