Methods to combat spam. What is spam and how to fight spammers on the Internet What methods of protection exist against spam


Dear friends and users of our site, I am with you again, SpaceWolf, and today we will talk about the pressing problem of “SPAM”. The solution to this problem will allow you to get rid of spam on the feedback form, spam comments or spam for orders in the online store.

I would like to immediately note the pros and cons of this method:

  1. Works well against bots.
  2. Quick installation in the message sending form
  3. Minimum code (3 lines)
  4. Does not require special knowledge, except for the location of the main files.
  5. Users who do not have java will not be able to pass the verification and therefore send a message.

Basically everything. Let's start the installation:

1) Add an additional hidden field to your form (this is a comment form, feedback form, product order form) with the name name=”check” meaning value=”” leave it blank. Example:

2) In the same form but only in the button (“send”, “write”, “Leave a review” or whatever you call it) add the following code:

If ($_POST["check"] != "stopSpam") exit("Spam decected");

Anti-spam protection - how it works

The principle is as simple as the code itself. It is designed to ensure that spam bots do not know how to run programs on JavaScript. When a regular user clicks on the “order” button in our hidden field, the word “stopSpam” will be entered, but in the case of a robot, this field will remain empty. Let me explain at this point why it will remain empty? The robot fills in all fields except our hidden ID field id=”check” and variable "check" will remain blank, therefore the mail will not be sent. And when the user clicks on the button, our JavaScript, which we added to the button.

I advise you to use this method in conjunction with captcha, the effect will be better.

Well, that's all. If the article helped you, write comments, repost and don’t forget to say “Thank you” in the comments.

If anyone has other problems or questions, leave them in the comments, we will be happy to find a solution together. We are waiting for your messages!

According to statistics, more than 80 percent of malware penetrates the local network through email. The mail server itself is also a tasty morsel for hackers - having gained access to its resources, the attacker gets full access to archives of emails and lists of email addresses, which allows them to obtain a lot of information about the life of the company, projects and work carried out in it. After all, even lists of email addresses and contacts can be sold to spammers or used to discredit a company by launching attacks on those addresses or composing fake emails.

At first glance, spam is a much lesser threat than viruses. But:

  • A large flow of spam distracts employees from performing their tasks and leads to an increase in non-production costs. According to some data, after reading one letter, an employee needs up to 15 minutes to get into a working rhythm. If more than a hundred unwanted messages arrive per day, then their need to view them significantly disrupts current work plans;
  • spam facilitates the penetration of malware into the organization, disguised as archives or exploiting vulnerabilities of email clients;
  • a large flow of letters passing through the mail server not only degrades its performance, but also leads to a decrease in the available part of the Internet channel and an increase in the cost of paying for this traffic.

Spam can also be used to carry out some types of attacks using social engineering methods, in particular phishing attacks, when the user receives letters disguised as messages from completely legal individuals or organizations, asking them to perform some action - for example, enter a password for their account. bank card.

In connection with all of the above, the email service requires protection without fail and first of all.

Description of the solution

The proposed solution for protecting an enterprise's email system provides:

  • protection against computer viruses and other malicious software distributed via email;
  • protection against spam, both arriving to the company by e-mail and distributed over the local network.

Modules can be installed as additional modules of the protection system;

  • protection against network attacks on the mail server;
  • anti-virus protection of the mail server itself.

Solution Components

The mail service protection system can be implemented in several ways. The choice of the appropriate option is based on:

  • the information security policy adopted by the company;
  • operating systems, management tools, security systems used in the company;
  • budget restrictions.

The right choice allows you not only to build a reliable protection scheme, but also to save a significant amount of money.

As examples, we give the options “Economy” and “Standard”

The “Economy” option is built on the Linux operating system and makes maximum use of free products. Composition of the variant:

  • anti-virus and anti-spam subsystem based on products from Kaspersky Lab, Dr.Web, Symantec. If your company uses a demilitarized zone, it is recommended to move the mail traffic protection system into it. It should be noted that products designed to work in the demilitarized zone have greater functionality and greater capabilities for detecting spam and attacks than standard ones, which improves network security;
  • firewall subsystem based on iptables2 firewall and management tools standard for the Linux operating system;
  • attack detection subsystem based on Snort.

Mail server security analysis can be done using Nessus

The solution based on the “Standard” option includes the following subsystems:

  • subsystem for protecting mail server and mail gateway services from malware based on solutions from Kaspersky Lab, Dr.Web, Eset, Symantec or Trend Micro;
  • firewall and attack detection subsystem based on Kerio Firewall or Microsoft ISA.

Mail server security analysis can be done using XSpider

Both options above do not include instant messaging and webmail security modules by default
Both the “Economic” option and the “Standard” option can be implemented on the basis of software products certified by the FSB and FSTEC, which allows them to be supplied to government agencies and companies with an increased level of security requirements.

Advantages of the proposed solution

  • the solution provides reliable protection against the penetration of malware and spam;
  • Optimal selection of products allows you to implement a protection scheme that takes into account the needs of a specific client.

It should be noted that a full-fledged security system can only function if the company has an information security policy and a number of other documents. In this regard, Azone IT offers services not only for the implementation of software products, but also for the development of regulatory documents and auditing.

You can obtain more detailed information about the services provided by contacting the specialists of our company.

Modern spam mailings are distributed in hundreds of thousands of copies in just a few tens of minutes. Most often, spam comes through user computers infected with malware - zombie networks. What can be countered to this onslaught? The modern IT security industry offers many solutions, and anti-spammers have various technologies in their arsenal. However, no existing technology is a magic “silver bullet” against spam. There is simply no universal solution. Most modern products use multiple technologies, otherwise the effectiveness of the product will not be high.

The most well-known and common technologies are listed below.

Blacklists

They are also DNSBL (DNS-based Blackhole Lists). This is one of the oldest antispam technologies. Block mail coming from IP servers listed in the list.

  • Pros: The blacklist 100% blocks mail from a suspicious source.
  • Minuses: They produce a high rate of false positives, so should be used with caution.

Crowd control (DCC, Razor, Pyzor)

The technology involves identifying mass messages in the mail flow that are absolutely identical or differ only slightly. To build a working “mass” analyzer, huge mail flows are required, so this technology is offered by large manufacturers who have significant volumes of mail that they can analyze.

  • Pros: If the technology worked, then it was guaranteed to detect a mass mailing.
  • Minuses: Firstly, a “large” mailing may not be spam, but quite legitimate mail (for example, Ozon.ru, Subscribe.ru send thousands of almost identical messages, but this is not spam). Secondly, spammers know how to “break through” such protection using intelligent technologies. They use software that generates various content - text, graphics, etc. - in every spam letter. As a result, crowd control does not work.

Checking Internet Message Headers

Spammers write special programs to generate spam messages and distribute them instantly. At the same time, they make mistakes in the design of headers; as a result, spam does not always comply with the requirements of the RFC mail standard, which describes the header format. These errors can be used to identify a spam message.

  • Pros: The process of recognizing and filtering spam is transparent, regulated by standards and quite reliable.
  • Minuses: Spammers are learning quickly, and spam header errors are becoming fewer and fewer. Using this technology alone will allow you to stop no more than a third of all spam.

Content filtering

Also one of the old, proven technologies. The spam message is checked for the presence of spam-specific words, text fragments, pictures and other characteristic spam features. Content filtering began with the analysis of the message subject and those parts of it that contained text (plain text, HTML), but now spam filters check all parts, including graphic attachments.

As a result of the analysis, a text signature can be built or the “spam weight” of a message can be calculated.

  • Pros: Flexibility, ability to quickly fine-tune. Systems running on this technology easily adapt to new types of spam and rarely make mistakes in distinguishing between spam and normal mail.
  • Minuses: Updates are usually required. Filter settings are carried out by specially trained people, sometimes by entire antispam laboratories. Such support is expensive, which affects the cost of the spam filter. Spammers invent special tricks to circumvent this technology: they introduce random “noise” into spam, making it difficult to find spam characteristics of a message and evaluate them. For example, they use non-literal symbols in words (this is how, for example, the word viagra may look when using this technique: vi_a_gra or vi@gr@), generate variable colored backgrounds in images, etc.

Content filtering: Bayes

Statistical Bayesian algorithms are also designed for content analysis. Bayesian filters do not require constant tuning. All they need is prior training. After this, the filter is adjusted to the email topics that are typical for this particular user. Thus, if a user works in the education system and conducts training, then personally messages on this topic will not be recognized as spam. For those who do not need offers to attend training, the statistical filter will classify such messages as spam.

  • Pros: Customization.
  • Minuses: Works best on individual mail flow. Setting up Bayes on a corporate server with heterogeneous mail is a difficult and thankless task. The main thing is that the end result will be much worse than for individual boxes. If the user is lazy and does not train the filter, then the technology will not be effective. Spammers specifically work to bypass Bayesian filters, and they succeed.

Greylisting

Temporary refusal to receive a message. The refusal comes with an error code that is understood by all mail systems. After some time they resend the message. And programs that send spam do not resend the letter in this case.

  • Pros: Yes, this is also a solution.
  • Minuses: Delay in mail delivery. For many users, this solution is unacceptable.

Blacklists

Blacklists include IP addresses from which spam is sent.

To configure, go to the section Spam protection-> Blacklists and click the "Create" button. In field Sender specify the IP address of the mail server (or the first digits of this address), the mail domain, or a separate email address for which mail forwarding will be prohibited (depending on the installed mail client, the entry formats will vary).

Greylisting

The principle of operation of gray lists is based on spamming tactics. As a rule, spam is sent in a very short time in large quantities from some server. The work of a gray list is to deliberately delay the receipt of letters for some time. In this case, the address and time of forwarding are entered into the gray list database. If the remote computer is a real mail server, then it must store the letter in a queue and resend it within five days. Spambots, as a rule, do not save letters in the queue, so after a short time they stop trying to forward the letter. When resending a letter from the same address, if the required amount of time has passed since the first attempt, the letter is accepted and the address is added to the local white list for a sufficiently long period. One of the disadvantages of the method is the possibility of a mail delivery delay of 15 minutes or more, depending on the sender’s server settings.

Greylisting is configured in the Greylisting module, where you need to specify the required parameters. Greylisting in the ISPmanager panel works through two applications - Milter-greylisting and Postgrey, which must first be activated in the Features section.

dnslb blocking

DNSBL (DNS blacklist) - lists of hosts stored using the DNS system. The mail server contacts the DNSBL and checks it for the IP address from which it is receiving the message. If the address is in this list, then it is not accepted by the server, and a corresponding message is sent to the sender

In chapter Spam protection Select dnsbl blocking, click the New button and add a new dnsbl blocking list. In field Block list specify the block list domain name. This server will request information about the presence of a particular mail server on the black list.

Here you can find the most common block lists: http://www.dnsbl.info/dnsbl-list.php

Message limit

Another way to combat spam is to set a limit on the number of messages.

This functionality is available if you have Exim installed.

SpamAssasin

The SpamAssasin (SA) program allows you to analyze the contents of an already delivered letter. You can add appropriate lines to the letter headers, and the user, based on mail filters in the mail client, can filter mail into the necessary folders of the mail program.

To be able to use SA in the ISPmanager panel, activate it in the Capabilities module. By default, after activation, the automatic self-learning function will be enabled, but, in addition, the effectiveness of spam retention can be significantly increased using “manual” filter training.

Setting up a mailbox and mail domain

To completely disable Greylisting checking for any recipient address or domain (for example, if you do not want the mail to be subject to this check), go to the module


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