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Anti-spam technologies
Spam filtering techniques
To combat spamming, software publishers use a variety of technologies and methods to catch unwanted messages. But what are these different methods of analyzing our messages?
The messages you receive can be analyzed upstream of your workstation, on the mail server, or directly on your workstation. Anti-spam technologies analyze the various elements present in the message, such as the sender’s IP, SMTP protocol, mail header, mail body, attachments, sender’s address, sender’s domain name, etc. This information is analyzed differently depending on the technology.
In the technologies used by software, lexical analysis is a method based on the content of incoming messages, analyzing it to detect keywords or expressions that characterize spam. This method is complemented by shape analysis. The latter observes the color code used, the presence of images and the style of the e-mail.
In addition to these analyses, anti-spam software also works with restrictive lists. This blacklist technology provides you with a list of servers or networks known to be spamming. Unlike blacklists, there are also whitelists. The latter provide secure sites, servers or networks. Software suppliers have set up collaborative spam databases. These bases evolve according to each person’s spam submissions.
Anti-spam software editors also use other technologies such as Bayesian filters. These filters work by analyzing incoming e-mails against criteria of words frequently present in authorized e-mails and in e-mails recognized as spam. After analysis, two percentages emerge: a percentage of legitimacy or illegitimacy. In addition to Bayesian filters, anti-spam software also uses trend analysis. This last analysis enables incoming messages to be controlled according to the analysis of e-mails sent by the user.
Anti-spam software has recently adopted two new technologies. Teergrubing: by keeping a session open for a long time, it prevents spam from being sent to other recipients. Greylisting, which works by temporarily rejecting messages by sending a refusal code to the sending server. Based on the fact that the spamming server doesn’t bother to resend spam after a certain period of time, if the message is resent it means it’s a valid message.
By combining these different technologies, software publishers are able to offer the market increasingly powerful software.
