Anti-Spam SMTP Proxy
Encyclopedia
The Anti-Spam SMTP Proxy (ASSP) server project is an Open Source
, Perl
based, platform-independent transparent SMTP proxy
server available at SourceForge.net that leverages numerous methodologies and technologies to both rigidly and adaptively identify e-mail spam
. ASSP is easy to set up because it requires only minor changes to the configuration of your Mail Transfer Agent
.
which makes it difficult to debug, and update. For example, the entire program is written as a single Perl program file, rather than being broken into modules
.
Open source
The term open source describes practices in production and development that promote access to the end product's source materials. Some consider open source a philosophy, others consider it a pragmatic methodology...
, Perl
Perl
Perl is a high-level, general-purpose, interpreted, dynamic programming language. Perl was originally developed by Larry Wall in 1987 as a general-purpose Unix scripting language to make report processing easier. Since then, it has undergone many changes and revisions and become widely popular...
based, platform-independent transparent SMTP proxy
Transparent SMTP proxy
SMTP proxies are specialized Mail Transfer Agents that, similar to other types of proxy servers, pass SMTP sessions through to other MTAs without using the store-and-forward approach of a typical MTA. When an SMTP proxy receives a connection, it initiates another SMTP session to a destination MTA...
server available at SourceForge.net that leverages numerous methodologies and technologies to both rigidly and adaptively identify e-mail spam
E-mail spam
Email spam, also known as junk email or unsolicited bulk email , is a subset of spam that involves nearly identical messages sent to numerous recipients by email. Definitions of spam usually include the aspects that email is unsolicited and sent in bulk. One subset of UBE is UCE...
. ASSP is easy to set up because it requires only minor changes to the configuration of your Mail Transfer Agent
Mail transfer agent
Within Internet message handling services , a message transfer agent or mail transfer agent or mail relay is software that transfers electronic mail messages from one computer to another using a client–server application architecture...
.
Features
Some ASSP's features are:- Bayesian analysisBayesian spam filteringBayesian spam filtering is a statistical technique of e-mail filtering. It makes use of a naive Bayes classifier to identify spam e-mail.Bayesian classifiers work by correlating the use of tokens , with spam and non spam e-mails and then using Bayesian inference to calculate a probability that an...
- Penalty Box (PB) trapping
- DNSBLDNSBLA DNSBL is a list of IP addresses published through the Internet Domain Name Service either as a zone file that can be used by DNS server software, or as a live DNS zone that can be queried in real-time...
/RBL (Realtime Blackhole Listing) - URIBL (Uniform Resource IdentifierUniform Resource IdentifierIn computing, a uniform resource identifier is a string of characters used to identify a name or a resource on the Internet. Such identification enables interaction with representations of the resource over a network using specific protocols...
Black Listing) - Multi-level SPFSender Policy FrameworkSender Policy Framework is an email validation system designed to prevent email spam by detecting email spoofing, a common vulnerability, by verifying sender IP addresses. SPF allows administrators to specify which hosts are allowed to send mail from a given domain by creating a specific SPF...
(Sender Policy Framework) validation and blocking - SRSSender Rewriting SchemeSender Rewriting Scheme is a technique to re-mail an email message so that eventual Delivery Status Notifications can reach the original message sender...
(Sender Rewriting Scheme) fix-up - Session Delaying/GreylistingGreylistingGreylisting is a method of defending e-mail users against spam. A mail transfer agent using greylisting will "temporarily reject" any email from a sender it does not recognize. If the mail is legitimate the originating server will, after a delay, try again and, if sufficient time has elapsed, the...
and connection response delaying - Sender validation and recipient validation
- Multi-level attachment blocking (based on block lists or allow lists)
- As well as multiple RFCRequest for CommentsIn computer network engineering, a Request for Comments is a memorandum published by the Internet Engineering Task Force describing methods, behaviors, research, or innovations applicable to the working of the Internet and Internet-connected systems.Through the Internet Society, engineers and...
validation mechanisms. - Multi-threadedThread (computer science)In computer science, a thread of execution is the smallest unit of processing that can be scheduled by an operating system. The implementation of threads and processes differs from one operating system to another, but in most cases, a thread is contained inside a process...
(Since version 2.x) - Platform independent (Written in PerlPerlPerl is a high-level, general-purpose, interpreted, dynamic programming language. Perl was originally developed by Larry Wall in 1987 as a general-purpose Unix scripting language to make report processing easier. Since then, it has undergone many changes and revisions and become widely popular...
)
Disadvantages
From a technical point of view, the software is written in an obfuscated styleObfuscated code
Obfuscated code is source or machine code that has been made difficult to understand for humans. Programmers may deliberately obfuscate code to conceal its purpose or its logic to prevent tampering, deter reverse engineering, or as a puzzle or recreational challenge for someone reading the source...
which makes it difficult to debug, and update. For example, the entire program is written as a single Perl program file, rather than being broken into modules
Modular programming
Modular programming is a software design technique that increases the extent to which software is composed of separate, interchangeable components called modules by breaking down program functions into modules, each of which accomplishes one function and contains everything necessary to accomplish...
.
See also
- Transparent SMTP proxyTransparent SMTP proxySMTP proxies are specialized Mail Transfer Agents that, similar to other types of proxy servers, pass SMTP sessions through to other MTAs without using the store-and-forward approach of a typical MTA. When an SMTP proxy receives a connection, it initiates another SMTP session to a destination MTA...
- SpamAssassinSpamAssassinSpamAssassin is a computer program released under the Apache License 2.0 used for e-mail spam filtering based on content-matching rules. It is now part of the Apache Foundation....
, popular open source spam filtering that uses razor and other techniques to detect spam. - QpsmtpdQpsmtpdqpsmtpd is an SMTP daemon written in Perl. It was originally designed to be a drop-in replacement for qmail-smtpd, the SMTP component of qmail, and it is now also compatible with Postfix, Exim, sendmail and virtually any software that "speaks SMTP"...
, a similar project