Unwanted messages are more than just minor annoyances. They fill up a user’s inbox, potentially exposing them to malicious software, files and applications. Installing an anti spam filter can be an excellent way to eliminate this threat. These programs typically work using one or more of the following methods.
Greylisting
If the filter receives a message from an unknown sender, it will temporarily reject it. If the email is legitimate, the server will try again and the email will be let through. Spammers, however, tend only to send messages once, a trend which can be used to automatically cut out a large percentage of unwanted mail.
Virus Rejection
Since the greatest threat spam offers is malware, the best filters will come with in-built scanning software which looks at any attachments and determines whether they are legitimate or not. Any malicious files will be deleted in some cases along with the email it is attached to.
Blackhole Lists
Over time, the creators of the top anti-spam filters will build up a list of IP addresses which are known as frequent offenders. By compiling these together into a blackhole list and then integrating this into their programs, a filter can be created which automatically knows which IPs are risky and which are probably safe.
Mail Forwarding
Since spammers are always adapting, anti-spam companies have to continually upgrade their lists of dangerous addresses. They can do this by forwarding all potentially malicious mail caught by their filters to a centralised database where they are stored and analysed so that new addresses can be added every day.
These are only a few of the many techniques which may be used by the world’s top spam filters for email. Combined together, they can eliminate the vast majority of unwanted messages from arriving in your inbox.