Spam has varying definitions, which varies depending on the source.
- Unsolicited Bulk Email (UBE): Sent in large quantities.
- Unsolicited Commercial Email (UCE): Used by regulators whose mandate is to monitor commerce information such as the US Federal Trade Commission any fraudulent email message. Any mail message where the actual email id of the sender is forged or those messages that are sent through unauthorized proxies, servers, or botnet.
- 419 Scams: Advance fee fraud such as the 419 scam may be sent by a single person in a developing country. Organized spam gangs in Russia or Eastern Europe may share many features common with other forms of organized crime that may also include revenge killings too.
- Phishing: Many users of the Internet fall prey to scamsters and may enter personal information on fake websites, which are made to appear real like the PayPal website. This activity is known as phishing. Spear phishing is the term given to the mode where in the email appears to have come from a person known to the user. For eg, from his employer.
- Appending: Suppose that a certain marketer has a database containing the names, addresses and telephone numbers of prospective customers, they can have their database matched against a database containing a list of valid email addresses by paying certain amount. But if the database itself contains erroneous information or there is a mismatch in the names of the people then many people would get Unsolicited Commercial Emails (UCE) creating a lot of discontent among the recipients. To protect against this type of fallacies, emails should be sent to users known to have subscribed.
- Image Spam: This is a clever ploy adopted by the spammers in which the text of the image is stored as a JPEG or a GIF image and is displayed in the email. This prevents the spam filters from detecting the message as spam. It is presently used largely to “pump and dump” stocks. Image spams often contain nonsensical data in images that can be read by new technology in few programs but these are not very accurate. Newer techniques include using animated GIF that doesn’t contain clear text in its initial frame or to contort the shapes of the letters in the image.
- Blank Spam: Spam lacking a payload advertisement. The message body as well as the subject line is missing altogether, but these messages qualify as spam since they are sent in bulk and are unsolicited in nature. It could have been intentional or not deliberate. They could have been sent in a directory harvest attack where in the goal of such an attack is to separate invalid addresses from the valid ones. In this case, the spammer may do away with typing the header and the message body. It could also occur when the spammer “forgets” to add the message. Poorly written spam software or shoddy relay servers could also truncate header lines from the server. Certain blank spams often carry a much heavy payload such as a virus or a worm where the message appears blank but is often very malicious. The VBS. Davinia. B. Email Worm is an example of this kind of attack.
- Backscatter Spam: It is one of the side-effects of email spam, viruses and worms, where by the email servers receiving the spam and other mail send bounce messages to an innocent party, since the envelope sender of the original message is forged to show the email address of the innocent victim. Such messages are bulk in nature, are not solicited by the sender, and hence qualify as spam. Systems that generate backscatter are listed in several DNSBLs.
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