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.

eco-friendly cleaning service Buffalo Grove ..

In The News:

AutoFlight's zero-carbon floating vertiport uses solar power to charge eVTOL aircraft while supporting emergency response, tourism, and marine energy maintenance.

A new phone return scam targets recent buyers with fake carrier calls. Learn how criminals steal devices and steps to protect yourself from this fraud.

New Anthropic research reveals how AI reward hacking leads to dangerous behaviors, including models giving harmful advice like drinking bleach to users seeking help.

The Fox News AI Newsletter gives readers the latest AI technology advancements, covering the challenges and opportunities AI presents.

Holiday email scams, including non-delivery fraud and gift card schemes, spike in November and December, costing victims hundreds of millions, the FBI says.

Holiday visits offer the perfect opportunity to help older parents with technology updates, scam protection and basic troubleshooting skills for safer digital experiences.

Swiss scientists create grain-sized robot that surgeons control with magnets to deliver medicine precisely through blood vessels in medical breakthrough.

Researchers exploited WhatsApp's API vulnerability to scrape 3.5 billion phone numbers. Learn how this massive data breach happened and protect yourself.

Travel companies share passenger data with third parties during holidays, but travelers can protect themselves by removing data from broker sites and using aliases.

Xpeng's humanoid robot moves so realistically that crowds believed it was fake, marking a major advancement in robotics technology ahead of 2026 commercial launch.

Researchers discover phishing scam using invisible characters to evade email security, with protection tips including password managers and two-factor authentication.

iPhone and Android users can reduce battery drain and data usage by restricting Background App Refresh to Wi-Fi connections instead of mobile networks.

Scammers nearly stole an Apple account by exploiting the support system with authentic-looking tickets and phone calls, users can protect themselves with safety steps.

FoloToy restored sales of its AI teddy bear Kumma after a weeklong suspension following safety group findings of risky and inappropriate responses to children.

Threat intelligence firm Synthient uncovers one of the largest password exposures ever, prompting immediate security recommendations.

Viral video shared by Elon Musk shows Tesla's Optimus humanoid robots performing tasks from cooking to construction, garnering over 58.5 million views on social media.

Chinese hackers used Anthropic's Claude AI to launch autonomous cyberattacks on 30 organizations worldwide, marking a major shift in cybersecurity threats.

Apple's new Sleep Score feature gives you a rating for your nightly rest quality. Learn how to set it up on your Apple Watch and iPhone today.

Essential phone settings to enable before losing your device, including Find My network, location services and security features for iPhone and Android.

The Fox News AI Newsletter gives readers the latest AI technology advancements, covering the challenges and opportunities AI presents.

Cybersecurity research shows weak passwords remain a major threat, with simple patterns and number sequences putting millions of accounts at risk.

New Android malware BankBot YNRK silences phones, steals banking data and drains crypto wallets automatically. Learn how this advanced threat works.

FDA approves first human trial for Paradromics' brain-computer interface that could restore speech for paralyzed patients through neural technology.

New phishing platform QRR targets Microsoft 365 users across 1,000 domains in 90 countries. Learn how to spot fake login pages and protect your accounts.

OpenTable now uses AI to track your dining habits and share insights with restaurants. Learn what data they collect and how to protect your privacy.

How Spammers Fool Bayesian Filters - And How to Stop Them

Spam Blocking