| div id="body" > Effectively stopping spam over the long-term requires much more than blocking individual IP addresses and email spam blocking 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 email spam blocking volume of spam. The old ways of blocking the bad guys just don t work anymore. Examining spam and email spam blocking spam-blocking technology can illuminate how this evolution is taking place and email spam blocking what can be done to combat spam and email spam blocking 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 email spam blocking 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 email spam blocking 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 email spam blocking sent as a regular update to the email service s subscribers. The signature is compared to every email coming in to the network and email spam blocking 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 email spam blocking the update is sent and email spam blocking 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 email spam blocking 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 email spam blocking 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 email spam blocking 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 http://www.ciphertrust.com and email spam blocking downloading our whitepapers. | 
