Spam filters - how they work and how to bypass them. Anti-spam methods on the providers' side


As you have already noticed, I am gradually moving away from the “ Information article” to format “ Step-by-step instruction" And as your responses to letters from my practical mailing list “Email Marketing - Money on Demand” showed, this best format worth sticking to! Today we will look at instructions on how to bypass spam filters.

Bypassing SPAM filters: why is it important?

Methods for bypassing spam filters are gaining more and more relevance every day.

Having a 40%+ email open rate and not falling into SPAM is only possible in 1 of 2 options:

  • You have a base of less than 500 people
  • You have a fresh database collected over the last week

Postal services know everything about you and your every step:

  • The number of dead email addresses in your database;
  • How many complaints were received from subscribers
    for the last month;
  • Know the number of paragraphs in your letter;
  • Known openability;
  • How many subscribers regularly
    delete your emails;
  • Until what paragraph does the subscriber read the letter?
  • How much time does the recipient spend
    to read the letter;

Thunderbird spam filter, Rambler spam filter - these are all flowers.

The basis that needs to be worked on is mail.ru and yandex.ru - email providers that occupy 70%+ of the entire market email addresses. Bypassing these spam filters is most important.

What you read below will be useful for:

  1. Authors who already run mailing lists and want to improve their email deliverability results + get to know their target audience better for better interaction with them.
  2. Those who want to effectively conduct their future mailings

So how to bypass spam filters? Where to begin? Who should I write to?

Step #1 “IN THE DOMAIN”

Right:
Kir@site

Wrong:
[email protected]

By using the domain name in the sender's address, you show the provider your true face, that is, the domain of your website, and not some “Vasya” from the yard who just registered a physical email yesterday.

Think about it for a second. It is the mail provider who decides whether to send your letter to the subscriber or not. The success of your mailings depends on what mail, yandex, gmail, rambler think about your mailings. You have to play by their rules if you want to beat the underdog spots.

Step No. 2 “Assessing the situation”

The analytics that you observe in your mailing services are not truthful, since they are not the primary source.

You need to register for 2 services mail providers, add your domain and undergo moderation:

  1. https://postoffice.yandex.ru/
  2. https://postmaster.mail.ru/

This will be your second sign of attention to email providers!

Step No. 3 “Digitalization of the database”

Your subscriber base can be compared to movies on disc.

Disk - subscriber base
Movies - Subscriber Segments

So, when you buy a licensed disc in a store, you know that it is not a fake and that you “fit in” with the quality. There will be no pirated recordings or other nonsense. The same cannot be said about discs that are bought at the market.

Make your database “licensed” - write down the key technical specifications, which will mark the beginning of your friendship with email providers.

What needs to be written down?

  1. DMARC

Who can do this?

  1. Hoster
  2. Technician (for example, layout designer)

Step No. 4 “First contact”

Now you need to contact postoffice and postmaster from those. support. Tell them you're all set up, that you're using white mail, and that you want to get better. Ask them for help, ask how you can improve.

For what?

Regards,
Kir Ulanov.

P.S.: Would you like to learn more about fighting spam?
Tell me exactly where your pain is concentrated"? Leave your comment below,
so that I understand what I should cook for you!

Today you won’t surprise anyone with spam. Everyone has received unwanted messages at least once in their life. emails, SMS and calls.

Phone numbers, addresses Email and other contact information for mailings are included in the database different ways(starting with the indication of the number in the application form when applying for a job and ending with the official consent specified in the contracts between the telecom operator and subscribers).

No matter how your data is obtained, avoid incoming unwanted messages you can unsubscribe from mailings (it’s worth noting right away that not all mailing companies operate legally and often do not provide such a function) or by correctly setting up a spam filter on a PC, smartphone, tablet and other devices with access to global network Internet.

And if everything is very clear with spam in email, click on the “spam” button and everything else Post service will do automatically (not to mention advanced training of spam algorithms of leading services based on your interests and preferences), then with SMS and telephone numbers everything is a little more complicated.

Below we will look at the procedure for setting up spam defense on smartphones under Windows control and Android.

How to use spam filter on Windows phone 10 and Nokia smartphones

IN currently governed by operating system Windows phone smartphones are no longer produced. With the advent of universal Windows platforms 10, the mobile operating system has received Windows name 10 Mobile.

Therefore, the procedures described below for setting up spam filtering may differ from those currently in effect. this moment(do not exclude the factor of development of a universal platform, into which changes are made with each new release, as well as additional interface add-ons integrated various manufacturers smartphones).

Spam filter on your phone on Windows phone

In order to activate access to the ability to block selected numbers in phone book, first of all, you need to go to the phone settings menu and find the “Spam filter” item, activate the blocking unwanted numbers– the “Block calls + SMS” checkbox (in smartphones from other manufacturers, the “Spam filter” settings item may have a different name, for example, “Call blocking”).

Now in the context menu, when you long tap on a selected contact in the call log, you can select the “block number” option (in third-party smartphones, this item may not be available in the call log, for example, only from the “People” application, which works with contact data).

You can only block phone numbers that are in your phone book or call log.

That is, in order to block a known number in advance that is not on your phone, you must either add it to your contact list or first dial it from your phone so that it appears in the call log.

If a number is included in such a “black list”, both calls and SMS messages will be blocked.

You can view and edit the list of already blocked numbers through the “Spam filter” settings menu - the “blocked numbers” button.

Some users complain about spam filter failure after updating the operating system. In this case, resetting your phone settings may help. This procedure should be performed very carefully, since not only all third-party applications will be deleted, but also user files stored in the phone’s memory. The latter should be transferred to a memory card in advance.

If the “Spam Filter” item has disappeared from the settings or was not there (the functionality is not provided by the manufacturer), you can use the original “callSMSfilter” application, which can be found and installed from the official store Microsoft applications(available also for downloading from the Windows 10 Mobile platform).

Spam filter on Windows 10 Mobile

In a modern operating room Windows system Mobile from third-party functionality the developers refused, and therefore the original Nokia spam protection was replaced with a built-in one system application— “Blocking and filtering.” You can add a subscriber to the black list, as before (in the Windows phone system), through context menu with a long tap.

Spam filter for Android – review

Due to the large number of Android smartphone manufacturers and operating system versions (including alternative firmware and modified original ones), functionality for blocking unwanted numbers for each specific device may differ significantly.

So, for example, to enable spam filter on Android smartphones Galaxy lines for SMS messages, you need to open the standard “Messages” application and long tap on the selected number (sender) to activate additional elements management. One of the icons that appears is responsible for marking the selected number as spam.

Advanced blocking settings can be found in the application settings (“Spam filter” item):

  • you can add a contact from your address book,
  • dial the number manually or set a condition (“starts with ...”, “ends with ...”, “contains ...” and “exact match”),
  • create a list of “stop words” based on which messages will be automatically marked as spam,
  • and also automatically block messages from unknown senders.

It’s worth noting right away that you won’t be able to mark messages sent from alphabetic names as spam.

To block unwanted calls you will need to install third party application from the Play Store.

Owners alternative firmware CM (CyanogenMod) does not need to be installed. The smartphone settings have everything you need. In the “Confidentiality” menu you can fill out your “black list”. Both messages and calls will be filtered. It is possible to set regular expressions, filter hidden and unknown numbers into spam.

Third-party applications that provide the required anti-spam protection in official store There are a lot of applications from Google. Let's look at a few of the brightest representatives.

2GIS Dialer Calls and contacts

Replaces standard application to make calls. It can not only identify incoming numbers based on its own data stored on the servers of the 2GIS company (a huge database of companies with addresses and telephone numbers), but also block calls based on a “black list”. It is possible to exchange new spam numbers among program users (the latter add special notes). The application does not work with SMS messages.

Silent SMS SPAM

Interesting application from Russian developer, which can work with short and text numbers of senders. Does not display any notifications or make any sounds when receiving spam. You can build the conditions for placement in spam not only on the basis of black lists (prohibited contacts), but also on the basis of white lists (allowed contacts). It is very finely customizable, but has not been updated for a long time (since 2014), although it works on modern smartphones.

SMSCop

You can download a spam filter based on the program’s own database, fine-tune the filters and create your own blocking list. Directly from the application, you can complain about the sender to the FAS (you must enter your passport data).

I could put all my boxes in a pile. But I ran into a problem: when all the messages come to one email, then you start to notice spam. And too lazy to climb and delete spam by hand, and the filter that is already built into the mail service is not always pleasing.

Why not make a bot that cleans mail, especially since spam is clearly visible based on certain signs?
Here's what I highlighted that was spam in my eyes:
- everything is written in uppercase
- messages where the main idea is: porn, dating, casinos, money, etc.
- if someone regularly sends email and I don’t read it

At the very beginning, you need to configure imap php to work closely with mail. Then write some algorithms, which are in this article will not be optimal, because everyone needs their own filter (for example, some expect spam from pornographic sites).

There will only be ideas and information for the mind. And for those who want to install their own filter, there will already be a foundation.

Begin...
There are a lot of articles about how to set up imap php, you can search for them. I have Ubuntu, I solved this issue in a couple of minutes and a little change in the settings.

When you have already configured imap, you can connect it.
//settings for connecting to mail
$imapaddress = "(imap.gmail.com:993/imap/ssl)";
$imapmainbox = "INBOX";
$maxmessagecount = 10;
$user="gmail email name without @gmail.com";
$password="long and complex password";

//our function that removes spam
spam_delete($imapaddress, $imapmainbox, $user, $password, $maxmessagecount);

Now we go to the post office and pick up the letters. When we take the letter, we divide the entire text into words and count the number. Then in a loop we take words by word and check whether this word can confirm that this letter is spam. Some points that in my opinion are spam are described above. Then we find the probability that this letter is spam using the following formula:

Probability = number of total words in the letter / words that did not pass the filter

Here's how it all works in code:
function spam_delete($imapaddress, $imapmainbox, $imapuser, $imappassword, $maxmessagecount)
{
$imapaddressandbox = $imapaddress . $imamainbox;

//open a connection with mail
$connection = imap_open ($imapaddressandbox, $imapuser, $imappassword)
or die("Can"t connect to "" . $imapaddress .
"" as user "" . $imapuser.
"" with password "" . $imappassword .
"": " . imap_last_error());

Echo "Gmail information for ". $imapuser."";

Echo "Inbox headers\n";
$headers = imap_headers($connection)
or die("can"t get headers: " . imap_last_error());

//count the number of emails on the site, we can display a maximum of 10
$totalmessagecount = sizeof($headers);

Echo $totalmessagecount . "messages";

If ($totalmessagecount<$maxmessagecount)
$displaycount = $totalmessagecount;
else
$displaycount = $maxmessagecount;

Echo "Message bodies\n";
//go to the letter, take the content and check for spam
for ($count=1; $count<=$displaycount; $count+=1)
{
$body=imap_fetchbody($connection,$count,"2");
//break the entire letter into words
$text=explode(" ",$body);
$spam=0;
//count the number of words
$n=count($text);
for ($i=0;$i<$n;$i++) {
$spam+=test_spam($text[$i])==1:1?0;
}
//see what is the probability that this is spam
// we divide the number of words into possible words,
//which confirms that this is spam
$result=$n/$spam;
//if 50% is spam, then delete it
if ($result>0.5) (
imap_delete($connection,$count);
imap_expunge($connection);
}
}
//close imap
imap_close($connection);
}

The spam checking algorithm is very simple, it is written as an example. If you want to write a stronger and smarter algorithm, I advise you to read some of the chapters about spam in the book “Programming the Collective Mind.”

The algorithm performs two actions:
1. Identifies words that are most often found in spam
2. Checks for case, if everything is in upper case, then it is most likely spam.

The code itself:
//spam checking function
function test_spam ($string) (
//filter stages
//check by keywords
$array=array("porn" => 1, "dating" => 1, "casino" => 1, "buy" => 1);
if ($array[$string]==1) (return 1;)
//whether it is in upper case
if (strtolower($string)!==$string) (
return 1;
}
return 0;
}
?>

I tested it on two examples, it seems to work...

P.S. I will be very glad to hear how you deal with garbage. If you find an error in the code, don’t swear too much; this is just an example and a foundation for developing something more.

Spam filter is a program that is configured to process and filter incoming mail to the server according to certain parameters: IP address, stop words in the text of the letter and regular expressions, features of technical headers, etc.
Each major email service (Rambler, Yandex-mail, Mail.ru...) filters letters for spam, but still quite a large number of unwanted emails pass through spam filters undetected. Why this happens, and how to properly configure your mailbox to avoid this, you will learn in this article.

What is spam
Spam(spam) is unwanted advertising sent against the will of the recipient. The beginning of the spam boom on the RuNet can be considered the beginning of the 2000s, when the domestic segment of the Internet began to develop very actively. Spam has many varieties - spam mailings, flooding of guest books, forums and bulletin boards, ICQ spam, etc. In each specific case, they use their own methods of protecting against unwanted messages.
This article will cover all the main aspects of mail (e-mail) spam and protection against it.

Spam filter is protection against advertising?
Indeed, at present, any mail service uses one or another spam filter. In addition, there are many antispam plugins for popular mail programs The Bat, Outlook Express and others. But at the same time, spam is flying into our inboxes with renewed vigor. But the worst thing, in my opinion, is different. The fact is that as a result of the merciless fight against spammers, many normal letters are sometimes lost, which can sometimes be very important. It was the problem with the delivery of important mail that prompted me to write this article, and I hope it will help reduce the flow of all kinds of garbage into your mailbox, and accordingly reduce the number of lost important letters.

How does a spam filter work?.
Antispam filters work according to various algorithms, but the main thing for everyone is the analysis of the letter upon receipt according to certain characteristics. All advertising letters from spammers are written according to a template. After all, a spammer will not write each letter manually when he has an e-mail database of 1 million or more addresses. And as soon as he launches a mailing list (you can’t send such a volume of letters instantly), and the first recipients of his letters complain about spam, then this mailing list will be immediately blacklisted, and all subsequent letters will be cut off by antispam filters using this system. These are so-called early warning systems that allow you to block a spammer at an early stage of mailing.
Another method is based on more detailed study letters, and identifying signs of spam mailing in it. If the letter is replete with words: Advertising, special offer, buy, discounts, sale... etc. That this letter will be clearly marked as suspicious. The letter may contain a non-existent sender's address, which is easy to check, or the address may be on a blacklist. Instead of text, there may be a picture with an advertisement placed. Normal letters, as a rule, do not contain big size text. And letters from the creators of various kinds of pyramids contain a large amount of information, which indicates what, where, how and why you need to buy part of some miracle program, and so on in this spirit.

This type of antispam filters usually has flexible settings on the user's side. The main thing here is not to go too far. The owner of the mailbox can personally indicate which maximum size to skip letters, which addresses to add to the blacklist, filter messages by subject of letters and words in the body of the letter. Is it true this method not suitable for people who have active email correspondence. After all, it is impossible to warn all senders to indicate, for example, in the subject line of the letter keyword, and as a rule, many senders do not know each other in advance.

Morality– the decision whether a letter is spam is made by the program, not by a person. But the program is not characterized by one quality - artificial intelligence, and therefore all spam filters, if desired, can be easily bypassed, or, more simply, deceived.

How to bypass the spam filter? Easily!
And yet, bypassing antispam systems is not easy, but very simple. This is confirmed by the fact that the problem of spam is still relevant. Only one person can make a 100% correct decision about whether this letter is needed or not! And this person is the recipient of the letter. Indeed, what if a person subscribes to advertising mailing from some company. But this is all polemic, and now the facts. Since the letter is filtered by antispam systems based on one or another criterion, then the spammer only needs to compose a “harmless” letter, i.e. the letter is as similar as possible to a regular one (needed by the recipient). The expression: “Brevity is the sister of talent” is very appropriate here. The shorter the letter, the more difficult it is to highlight the details characteristic of spam.
It is necessary to minimize the content of advertising words in the letter as much as possible, and modify the remaining ones. The word “Advertising” can be written like this:
Advertising(spaces between letters), Advertising(letters separated by dashes), Advertising(here the Russian letters “e” and “a” are replaced with similar Latin ones). As you can see, there are many options; for a person, any word will have the meaning “Advertising,” but many antispam systems will not understand this.
As for bypassing antispam systems that work on the principle of early detection of spam mailings, here it is enough to create a couple of dozen different templates in advance, and after each mailing of 100 thousand letters, change the letter template, domain and e-mail of the sender. This approach is widely used in spam bot networks (a network of infected user computers).

How to prevent your emails from being sent to junk mail?

After all, everyone who has been involved in email distribution for quite a long time has probably encountered this problem. On average, “thanks to” spam filters, about 10-20% of all emails disappear without a trace in the vast cyberspace. And all this is due to overzealous spam filters.

You don't even have to be a malicious spammer to have your correspondence deleted.

Alas, but fast and simple solution there is no problem. To avoid filters, you need to understand their nature, understand how they work. And this process is very long and scrupulous.

E-mail programs are very big list criteria that filters are guided by in order to recognize “junk” email. This list includes primarily "spam" phrases.

These include, for example: “ATTENTION, SALE!!!”, “CLICK HERE AND YOU WILL GET A MILLION DOLLARS!” Having recognized one of these phrases (or very similar to it), the mail robot disposes of the letter. Some criteria give more points, some less. Here, for example, is a sample analysis of criteria from “Spam Assassin”. This is the most popular spam filter in the world.

So, the email will be sent to spam, if it:

  • mentions winning huge sums of money (0.2 points);
  • asks why pay more? (1.25 points);
  • guarantees a refund for anything (2 points);
  • contains an appeal about some urgent issue that cannot be delayed (2.9 points);
  • offers cheap mortgages or refinancing (3 points);
  • tells the secret of unprecedented success (2.4 points);

If your email contains more spam than a certain threshold, it will be deleted.

Of course, you immediately want to ask, at what level is this threshold set? Unfortunately, there is no consoling answer. On each server, the administrator sets the bar individually. If the user is already fed up with junk mail, the threshold will be set very low. Almost ALL correspondence in this case will be sent to waste.

The list of criteria mentioned above for identifying spam is constantly growing, the filters themselves adapt to changes and new tricks of “spammers”. The list is updated every time the user clicks the "This is spam" button in their mailbox. Spam filters can even synchronize their work and exchange experiences online.

What are the common mistakes and how to avoid them?

  • Using spam phrases: “Click here!”, “Get a million in a minute!”;
  • An abundance of exclamation marks in the headers and body of the letter;
  • Abuse of the CAPS LOCK key;
  • Bright font colors, particularly red and green;
  • Incorrect encoding;
  • Using one large image instead of a text message. When the image is not accompanied minimum quantity text, the letter is deleted, recognized as spam;
  • Using the words “Test”, “Hello”, “Check”, “Test” in the subject line of the letter. This mistake is made by those who conduct test mailings within their corporate mail;
  • Sending one letter to multiple recipients within one organization. In this case the firewall mail client the company identifies the mailing as a spam attack. This difficult option, which no one can cope with postal service. Here everything depends only on system administrator companies;
  • Copy text from a document Microsoft Word to the mail. There is a discrepancy between the formats; text and Word in HTML format will not be displayed correctly. In particular, this applies to quotation marks and ellipses;

How do I know if emails end up in Trash or Junk?

To get started, analyze the open rate of mailing letters using


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