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.

recurring maid service Wilmette ..

In The News:

Google's discontinued Nest thermostats still secretly upload home data to company servers despite losing smart features, raising serious privacy concerns.

New Android malware NGate steals NFC payment codes in real-time, allowing criminals to withdraw cash from ATMs without your card. Learn protection tips.

DoorDash confirms data breach exposing customer names, emails, addresses after social engineering attack. Learn how to protect yourself from scams.

Concerned about Google's AI scanning your Gmail? Learn how to disable Gemini features that access your emails, Drive files and Chat messages for privacy.

Google warns Android users about dangerous fake VPN apps hiding malware that steals passwords, banking details and personal data from phones and tablets.

Apple's digital passport feature lets iPhone users breeze through TSA checkpoints this holiday season using Digital ID technology at 250+ airports.

A new phishing scam targets family photos with fake "Cloud Storage Full" alerts. Criminals steal credit card information through fake sites. Learn protection tips.

South Korean scientists create ultra-thin fabric muscles that turn clothes into robotic assistants, lifting 33 pounds while weighing under half an ounce.

Archer Aviation has acquired Hawthorne Airport for $126M to launch an LA air taxi network ahead of the 2028 Olympics, featuring AI-powered eVTOL operations and next-gen aviation tech.

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

Fake AI apps disguised as "ChatGPT" and "DALL·E" are flooding app stores with dangerous malware that steals data and monitors users without detection.

Fake buyers demand specific vehicle reports from unknown sites to steal credit card information from car sellers, but warning signs can help identify these scams before paying.

Android users can now manage apps across multiple devices more easily with Google Play Store's updated remote uninstall button in the latest update.

NASA's Perseverance rover discovers shiny metallic rock on Mars that could be a meteorite from an ancient asteroid, containing high levels of iron and nickel.

Holiday scams spike during Black Friday and Cyber Monday as criminals exploit your leaked personal data. Learn how to protect yourself from fake stores and phishing.

Commerce Department proposes TP-Link router ban over Chinese security risks. Learn how this potential prohibition could affect your home network and devices.

Hyundai AutoEver America suffered a data breach affecting 2,000 current and former employees, exposing names, Social Security numbers and driver's license information.

Washington court rules automated license plate reader images are public records, even when stored by vendors like Flock Safety, setting precedent for transparency.

Fake airline texts claiming flight cancellations are targeting travelers with convincing scams. Learn how cybercriminals steal personal data and credit card info.

Discover how iOS 26's new Adaptive Power feature automatically extends iPhone battery life by learning your usage patterns and adjusting performance intelligently.

New TikTok malware campaign tricks users into running PowerShell commands that download Aura Stealer, which steals credentials and authentication tokens.

Gaia Family offers fixed upfront pricing for IVF cycles with unlimited embryo transfers and financial protection, partnering with over 100 U.S. fertility clinics.

The Jetsons Act aims to position Pennsylvania as a leader in advanced air mobility by establishing regulations for hybrid ground-air vehicles.

Fake Geek Squad invoice emails are targeting users with convincing charges and urgent phone numbers to steal personal information and money.

Fox News Digital's artificial intelligence newsletter digs into a robot in Russia that faceplanted, George Clooney's alarm and OpenAI's rivalry with the New York Times.

How Spammers Fool Bayesian Filters - And How to Stop Them

Spam Blocking