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ANTI SPAM: Proof-of-work systems

http://antispamkill.blogspot.com/2007/07/proof-of-work-systems.html

Such as hashcash require that a sender pay a computational cost by performing a calculation that the receiver can later verify. Verification must be much faster than performing the calculation, so that the computation slows down a sender but does not significantly impact a receiver. The point is to slow down machines that send most of spam—often. Millions and millions of them. While every user that wants to send email. Techniques for researchers and law enforcement. Spam report feedback loops.

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ANTI SPAM: Background checks

http://antispamkill.blogspot.com/2007/07/background-checks.html

Since spammers are frequently kicked off the network. They are constantly trying to create new accounts. Many spammers are able to make even a few hours profitable for them and can cause many days of damage to reputation of the services they abused. As a result, many ISPs and web -email providers use CAPTCHAs on new accounts and try to verify the credit cards are not stolen before accepting new customers, check. ROKSO list and do other background checks. Techniques for researchers and law enforcement.

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ANTI SPAM: Greylisting

http://antispamkill.blogspot.com/2007/07/greylisting.html

The SMTP allows for temporary rejection of incoming messages. Greylisting is the technique to temporarily reject messages from unknown sender mail servers. A temporary rejection is designated with a 4xx error code that is recognized by all normal MTAs, which then proceed to retry delivery later. Greylisting is based on the premise that spammers and spambots. But a standard component of any legitimate sender's server. Techniques for researchers and law enforcement. Spam report feedback loops.

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ANTI SPAM: Tarpits&Transparent SMTP proxy

http://antispamkill.blogspot.com/2007/07/tarpits-smtp-proxy.html

A tarpit is any server software. Which intentionally responds pathologically slowly to client commands. By running a tarpit which treats acceptable mail. Normally and known spam. Slowly or which appears to be an open mail relay, a site can slow down the rate at which spammers. Can inject messages into the mail facility. Many systems will simply disconnect if the server doesn't respond quickly, which will eliminate the spam. Techniques for researchers and law enforcement. Spam report feedback loops.

antispamkill.blogspot.com

ANTI SPAM: Confirmed opt-in for mailing lists

http://antispamkill.blogspot.com/2007/07/confirmed-opt-in-for-mailing-lists.html

Confirmed opt-in for mailing lists. Enting opt-in mailing lists: many means of gathering user e-mail addresses remain susceptible to forgery. For instance, if a company puts up a Web form to allow users to subscribe to a mailing list about its products, a malicious person can enter other people's e-mail addresses — to harass them, or to make the company. Appear to be spamming. (To most anti-spammers. If the company sends e-mail to these forgery victims, it is spamming,. Also known as verified opt-in.

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ANTI SPAM: Statistical content filtering

http://antispamkill.blogspot.com/2007/07/statistical-content-filtering.html

Statistical filtering was first proposed in 1998 by Mehran Sahami et al., at the AAAI-98 Workshop on Learning for Text Categorization. A statistical filter is a kind of document classification system, and a number of machine learning researchers have turned their attention to the problem. Statistical filtering was popularized by Paul Graham's influential 2002 article A Plan for Spam. Which proposed the use of naive Bayes classifiers to predict whether messages are spam. Ham") email submitted by users.

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ANTI SPAM: PTR/Reverse DNS checks

http://antispamkill.blogspot.com/2007/07/ptrreverse-dns-checks.html

The PTR DNS records in the reverse DNS can be used for a number of things, including:. Most e-mail Mail Transfer Agents (server software) use a FCrDNS verification and if there is a valid domain name, put it into the "Received:" trace header field. Some e-mail Mail Transfer Agents will perform FCrDNS verification on the domain name given on the SMTP HELO and EHLO commands. This can violate RFC 2821 and so e-mail is usually not rejected by default. Techniques for researchers and law enforcement. Greeting ...

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ANTI SPAM: Port 25 blocking

http://antispamkill.blogspot.com/2007/07/port-25-blocking.html

And routers can be programmed to not allow SMTP traffic (TCP port 25) from machines that are not supposed to run Mail Transfer Agents or send e-mail.[3] This practice is somewhat controversial when ISPs block. Home users, especially if the ISPs do not allow the blocking to be turned off upon request. E-mail can still be sent from these computers to designated smart hosts via port 25 and to other smart hosts via the e-mail submission port 587. Techniques for researchers and law enforcement.

antispamkill.blogspot.com

ANTI SPAM: Spam Harassment Reduction

http://antispamkill.blogspot.com/2007/07/spam-harassment-reduction.html

SHRED) is a recent proposal for a sender-at-risk protocol that aims to avoid some of the defects of earlier reputation and postage-based systems. There are a number of proposals for sideband protocols that will assist SMTP operation. The Anti-Spam. Techniques for researchers and law enforcement. Techniques for researchers and law enforcement. Spam report feedback loops. Limit e-mail backscatter&Egress spam filtering. Confirmed opt-in for mailing lists. Sender-supported whitelists and tags.