Spam Filter Blacklists and Whitelists
In order to be effective at distinguishing spam from legitimate emails, a spam filter needs to rely on various methods. Some of today’s most popular programs utilize blacklists and whitelists to filter out junk mail. As you’ve probably guessed, these counterparts are the exact opposite of one another. Senders listed on the blacklist are denied access to a particular email address while those on the whitelists are allowed. When combined with techniques such as Bayesian filtering and pattern matching, these lists better assure that a much lower volume of spam reaches your inbox.
Types of Blacklists
Whitelists are pretty dry and cut, but blacklists come in many different forms. Below are details one some of the most common types of blacklists:
IP Blockers: IP blacklists or blackhole lists, are huge repositories of IP addresses known for distributing spam. The organizations who manage these repositories use a variety of mechanisms to find out who is sending spam. These techniques range from human reporting to setting up decoy email accounts. Many spam filters are configured to examine incoming email and trace its origin. If it comes from an IP address of a known spammer, it is flagged accordingly and moved to a quarantine folder. IP addresses can be blocked by email server, local machine or an entire country.
DNS Blacklists: DNS (Domain Name System) blacklists contain lists of IP addresses that act as the source of spam messages. By using this list, the spam filter can deny access to individual domains or websites. DNS blacklists are usually established and managed by anti-spam organizations.
Email Blacklists: Also known as spam blacklists, email blacklists contain information on email addresses and mail servers used by spammers. Using this type of list gives a spam filter the ability to deny access at the server and automatically discard unsolicited mail. Unfortunately, it could also deny legitimate messages as well.
Factors to Consider
Although using a spam filter equipped with blacklist and whitelist functionality will definitely help at keeping spam out, take note that such a system isn’t always accurate. In order to block a higher amount of unwanted email, spam filters must receive frequent updates as spammers grow more sophisticated by the day. Some create new email addresses to deliver spam from and others concoct new keywords that allow them to slip through the filter. The good thing is that blackslists are continuously updated by various Internet Service Providers and organizations. When your spam filter is regularly updated, the blacklist has a better chance of keeping out spam while the whitelist does a better job at reducing false positives and allowing genuine email to reach you.
Leave A Comment