Home
>
Spam Blocking
>
How Spammers Fool Rule-based and Signature-Based Spam Filters

How Spammers Fool Rule-based and Signature-Based Spam Filters

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.

Heuristics (Rule-based Filtering)

One method used to combat spam is Rule-based, or Heuristic Filtering. Rule-based filters scan email content for predetermined words or phrases that may indicate a message is spam. For example, if an email administrator includes the word "sex" on a company's rule-based list, any email containing this word will be filtered.

The major drawback of this approach is the difficulty in identifying keywords that are consistently indicative of spam. While spammers may frequently use the words "sex" and 'Viagra" in spam emails, these words are also used in legitimate business correspondence, particularly in the healthcare industry. Additionally, spammers have learned to obfuscate suspect words by using spellings such as "S*E*X", or "VI a a GRR A".

It is impossible to develop dictionaries that identify every possible misspelling of "spammy" keywords. Additionally, because filtering for certain keywords produces large numbers of false positives, many organizations have found they cannot afford to rely solely on rule-based filters to identify spam.

Signature-Based Spam Filters

Another method used to combat spam is Signature-based Filtering. Signature-based filters examine the contents of known spam, usually derived from honey pots, or dummy email addresses set up specifically to collect spam. Once a honey pot receives a spam message, the content is examined and given a unique identifier. The unique identifier is obtained by assigning a value to each character in the email. Once all characters have been assigned a value, the values are totaled, creating the spam's signature. The signature is added to a signature database and sent as a regular update to the email service's subscribers. The signature is compared to every email coming in to the network and all matching messages are discarded as spam.

The benefit of signature-based filters is that they rarely produce false-positives, or legitimate email incorrectly identified as spam. The drawback of signature-based filters is that they are very easy to defeat. Because they are backward-looking, they only deal with spam that has already been sent. By the time the honey pot receives a spam message, the system assigns a signature, and the update is sent and installed on the subscribers' network, the spammer has already sent millions of emails. A slight modification of the email message will render the existing signature useless.

Furthermore, spammers can easily evade signature-based filters by using special email software that adds random strings of content to the subject line and body of the email. Because the variable content alters the signature of each email sent by the spammer, signature-based spam filters are unable to match the email to known pieces of spam.

Developers of signature-based spam filters have learned to identify the tell-tale signs of automated random character generation. But as is often the case, spammers remain a step ahead and have developed more sophisticated methods for inserting random content. As a result, most spam continues to fool signature-based filters.

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.

residential cleaning services Lincolnshire ..

In The News:

Police departments across the U.S. and Canada are adopting virtual reality training to better prepare officers for high-pressure, real-world situations.

House Bill 469 would prevent AI systems from owning property, serving as executives, or gaining legal personhood in Ohio under Representative Thaddeus Claggett's proposal.

Public voter records expose retirees' personal details to election scammers who create targeted cons using names, addresses, and voting history data.

Instead of fearing what comes next with artificial intelligence, think outside the box. Here are high-earning AI jobs that don't require a computer science degree.

OpenAI CEO Sam Altman says polite words like "please" and "thank you" cost millions annually, while direct prompts may improve ChatGPT accuracy by several points.

Chattee Chat and GiMe Chat exposed intimate conversations and photos, revealing users spent up to $18,000 on AI companions before the breach.

New Instagram parental controls allow families to manage teen screen time and content limits through the Family Center with stricter safety settings.

Third-party security breach at Discord exposes sensitive user information including government IDs, highlighting cybersecurity risks from external service providers.

Survey of 1,000 students shows teens using AI for personal relationships while two-thirds of parents remain unaware of their children's AI usage.

Cybersecurity experts warn about a ShadowLeak vulnerability that weaponized ChatGPT's Deep Research agent to steal personal data from Gmail accounts through hidden commands.

Tesla's Full Self-Driving system faces federal investigation following 58 reports of crashes, with six vehicles running red lights before colliding with other cars.

The Fox News AI Newsletter brings you the latest developments on artificial intelligence, with news on OpenAI moving to soon allow erotica for adult users.

Eric Schmidt alerts that hackers can reverse-engineer AI models to bypass safety measures, citing examples like the jailbroken ChatGPT variant called DAN.

Cybercriminals exploit Microsoft Teams through impersonation, malicious links and fake profiles to gather intel and deliver ransomware to personal and work devices.

Google, Dior, Allianz and dozens of other companies lost sensitive customer data in Salesforce-related breaches affecting millions of records across multiple sectors.

Apple launches iOS 26 with new Preview app that combines document editing, PDF annotation and scanning features into one streamlined iPhone experience.

New AI road monitoring system uses sensor-embedded fabric to predict infrastructure problems, potentially reducing maintenance costs and traffic disruptions for cities.

Holiday charity scams target retirees through lookalike organization names, untraceable payment requests, and data broker information to steal donations.

The Federal Trade Commission says criminals are posing as IRS agents, law enforcement officers or other officials, often over the phone or online, to steal thousands of dollars at a time.

AI phishing scams now use voice cloning and deepfake technology to trick victims, but Kurt "CyberGuy" Knutsson reveals warning signs to watch for.

Inversion Space unveils Arc, a reusable reentry vehicle that can deliver up to 500 pounds of cargo from orbit to anywhere on Earth in under an hour.

Red flags like processing fees, urgent countdowns and requests for full Social Security numbers expose fraudulent settlement sites targeting consumers.

Comprehensive analysis of Google Maps, Waze and Apple Maps examines usability, routing accuracy, data handling and features across the top navigation platforms.

Expert analysis reveals whether wired Ethernet or wireless Wi-Fi connections are safer for home internet use, plus practical steps to secure your network from attackers.

Australian construction robot Charlotte uses sand, crushed brick and recycled glass to 3D print fireproof, floodproof homes with reduced carbon footprint.

How Spammers Fool Rule-based and Signature-Based Spam Filters

Spam Blocking