Home
>
Spam Blocking
>
How Spammers Fool Bayesian Filters - And How to Stop Them

How Spammers Fool Bayesian Filters - And How to Stop Them

Effectively stopping spam over the long-term requires much more than blocking individual IP addresses and creating rules based on keywords that spammers typically use. The increasing sophistication of spam tools coupled with the increasing number of spammers in the wild has created a hyper-evolution in the variety and volume of spam. The old ways of blocking the bad guys just don't work anymore.

Examining spam and spam-blocking technology can illuminate how this evolution is taking place and what can be done to combat spam and reclaim e-mail as the efficient, effective communication tool it was intended to be.

One method used to combat spam is Bayesian Filtering. Named after Thomas Bayes, an English mathematician, Bayesian Logic is used in decision making and inferential statistics. Bayesian Filers maintain a database of known spam and ham, or legitimate email. Once the database is large enough, the system ranks the words according to the probability they will appear in a spam message.

Words more likely to appear in spam are given a high score (between 51 and 100), and words likely to appear in legitimate email are given a low score (between 1 and 50). For example, the words "free" and "sex" generally have values between 95 and 98, whereas the words "emphasis" or "disadvantage" may have a score between 1 and 4. Commonly used words such as "the" and "that", and words new to the Bayesian filters are given a neutral score between 40 and 50 and would not be used in the system's algorithm.

When the system receives an email, it breaks the message down into tokens, or words with values assigned to them. The system utilizes the tokens with scores on the high and low end of the range and develops a score for the email as a whole. If the email has more spam tokens than ham tokens, the email will have a high spam score. The email administrator determines a threshold score the system uses to allow email to pass through to users.

Bayesian filters are effective at filtering spam and minimizing false positives. Because they adapt and learn based on user feedback, Bayesian Filers produce better results as they are used within an organization over time. They are not, however, foolproof. Spammers have learned which words Bayesian Filters consider spammy and have developed ways to insert non-spammy words into emails to lower the message's overall spam score. By adding in paragraphs of text from novels or news stories, spammers can dilute the effects of high-ranking words. Text insertion has also caused normally legitimate words that are found in novels or news stories to have an inflated spam score. This may potentially render Bayesian filters less effective over time.

Another approach spammers use to fool Bayesian filters is to create less spammy emails. For example, a spammer may send an email containing only the phrase, "Here's the link?". This approach can neutralize the spam score and entice users to click on a link to a Web site containing the spammer's message. To block this type of spam, the filter would have to be designed to follow the link and scan the content of the Web site users are asked to visit. This type of filtering is not currently employed by Bayesian filters because it would be prohibitively expensive in terms of server resources and could potentially be used as a method of launching denial of service attacks against commercial servers.

As with all single-method spam filtering methodologies, Bayesian filters are effective against certain techniques spammers use to fool spam filters, but are not a magic bullet to solving the spam problem. Bayesian filters are most effective when combined with other methods of spam detection.

The Solution

When used individually, each anti-spam technique has been systematically overcome by spammers. Grandiose plans to rid the world of spam, such as charging a penny for each e-mail received or forcing servers to solve mathematical problems before delivering e-mail, have been proposed with few results. These schemes are not realistic and would require a large percentage of the population to adopt the same anti-spam method in order to be effective. You can learn more about the fight against spam by visiting our website at www.ciphertrust.com and downloading our whitepapers.

Dr. Paul Judge is a noted scholar and entrepreneur. He is Chief Technology Officer at CipherTrust, the industry's largest provider of enterprise email security. The company's flagship product, IronMail provides a best of breed enterprise anti spam solution designed to stop spam, phishing attacks and other email-based threats. Learn more by visiting enterprise anti spam solution today.

Ancona limousine airport .. Lockport Chicago limo O’Hare

In The News:

Recent reports show many common passwords can be cracked in literally seconds. Kurt the CyberGuy explains how to strengthen your passwords.

Stay up to date on the latest AI technology advancements and learn about the challenges and opportunities AI presents now and for the future.

Iron, a robot that stands 5 feet, 8 inches tall and weighs 154 pounds, combines advanced artificial intelligence with human-like movement and exceptional vision.

Hertz, the rental car giant, recently confirmed that customer information was exposed through a cyberattack on one of its software vendors.

There are a number of features with AirPods you may or may not know about to take your listening experience to the next level. Kurt the CyberGuy explains.

These 35 Chrome extensions have privacy and security concerns. Tech expert Kurt “CyberGuy" Knutsson says to delete them now.

Tech expert Kurt “CyberGuy" Knutsson says 329,000 mph fusion rocket promises to be fast, disruptive and enable deep-space missions.

Stay up to date on the latest AI technology advancements and learn about the challenges and opportunities AI presents now and for the future.

Tech expert Kurt “CyberGuy" Knutsson says a new autonomous AI is a game changer that also raises privacy risks. Is your data safe?

Tech expert Kurt “CyberGuy" Knutsson says robots and drones are revolutionizing fruit farming with faster picking and smarter handling.

Landmark Admin revises May 2024 cyberattack scope to show twice as many people were affected. Kurt “CyberGuy" Knutsson gives tips to help stay safe from an insurance data breach.

Tech expert Kurt “CyberGuy" Knutsson talks about how Yamaha’s hydrogen outboard motor could revolutionize boating with zero emissions.

Tech expert Kurt “CyberGuy" Knutsson reveals how to memorialize or remove a deceased loved one’s Facebook account and protect their digital legacy from misuse or scams.

Tech expert Kurt “CyberGuy" Knutsson says an Apple Watch saved psychiatrist Amanda Faulkner by detecting deadly leukemia early.

Scammers and fraudsters are increasingly targeting the most vulnerable, especially nursing homes and the personal data of their residents. Kurt the CyberGuy has safety tips.

Infected USB flash drives can spread malware among multiple organizations in ways that can easily bypass traditional security systems.

With a fully automated warehouse system and AI-powered robots, Ocado's Hive picks, packs and delivers grocery store orders in just a few minutes.

Stay up to date on the latest AI technology advancements and learn about the challenges and opportunities AI presents now and for the future.

Recycling robots are using artificial intelligence to learn how to sort recyclables by recognizing patterns in colors, textures, shapes and logos.

The Reachy 2 robot is designed to be friendly and approachable, inviting natural interaction and is perfect for research, education and experimenting with embodied AI.

Kurt "CyberGuy" Knutsson shares several easy ways to keep your credit cards safe from digital thieves while you're traveling this summer.

Arcturus sets up cameras around the edges of baseball stadiums to capture real-time action and generate a 3D digital clone of the game.

Stay up to date on the latest AI technology advancements and learn about the challenges and opportunities AI presents now and for the future.

The CyberGuy explains why healthcare organizations are vulnerable to hackers after there have been a half dozen data breaches this year.

Developed at two California universities, the innovative technology combines brain-computer interfaces with advanced AI to decode neural activity into audible speech.

How Spammers Fool Bayesian Filters - And How to Stop Them

Spam Blocking