Spam is the electronic version of "junk mail," unsolicited e-mail that advertises a service or product.
Most spammers use spam to advertise, some use it to distribute viruses, trojans and worms while others simply use it to annoy. Email accounts are traditionally targeted most but recently spammers have become more innovative. Spam can now be found on blogs; instant messaging; social networking sites, such as MySpace and FaceBook; and even mobile phones.
While spam may not necessarily contain viruses or malware, it is a nuisance and results in loss of productivity when you are forced to sift through unwanted messages every day. For large organizations it can mean loaded email servers that threaten the health and operation of their IT systems. In extreme cases, spammers have secretly commandeered computers with malware to act as an email server, which is then used to forward spam messages to other email recipients.