Preventive measures

• One can improve somehow this situation by means of usage of new methods, based on specifically tuned filtrating. One of the developed programs is that one, offered by the staff of the Californian University, Los-Angels. The principle of the worked out idea is creation of so called "lists of allowance" directly by the user of particular mail-box. It means that you adjust your mail-box, entering names, e-mail and contact details of all persons you have or may have contacts into this list and letters only from those users will be allowed to your mail-box. The inconvenience of this method is that you have to do all this manually. Another weak point of this idea is that in case you have distributed your visit cards among important for you people, to your possible partners or in exhibition all letters from these new e-mail addresses will be taken for SPAM and will not be let.
  
  
• Another idea of SPAM protection is sender's existence checking. Any letter from the unknown sender will be kept for "quarantine" and the sender will be sent the request to confirm letter sending. Challenge response systems are used to raise expenses while dispatching SPAM. If this system determines a letter to be SPAM, the sender will receive a request. The recipient gets the letter only after the sender replies this request. All requests are divided into three groups: requests for the human intellect, computational requests and financial requests.
  
  a. Requests for the human intellect - Human challenges. In this case the sender has to enter letters, shown on the graphical image. This task is easy for any person, but if the request is well done it is absolutely impossible for computers. The weak points of this idea is that in case you are not in the "list of allowance" you will be sent these requests and it may take some time for you to reply it. If you manage to reply right your letter will be allowed to get the destination. SPAMers can use this technique by means of usage human resources. They just hire some students (for instance) and they will solve the sent task-requests.
  
  b. When a computer request is sent - computational challenges - the system of the computer has to solve a kind of puzzle. The recipient of the letter send the sender a puzzle, pieces of which are disordered. The sender of that letter should find right positioning of the pieces and send this solution back to the recipient. The systems checks this solution up and moves this letter from the SPAM folder to the inbox. The puzzle must be of that kind that the recipient could quickly create it and so quickly check the solution but at the same time necessitating time spending on its solution. The advantage of this computational challenges is obvious as it can be done automatically. If there is a standard for the computational challenges, the computer can be adjusted to solve quickly these tasks. In this case a user will not be disturbed - he / she sends a letter, the recipient's system automatically send the request and the system of the user also automatically replies and the recipient finally gets this letter. In order no to allow the SPAMers to solve these puzzles automatically, the necessary volume of calculations should be great and take from 30 seconds till 5 minutes. If the puzzle is easy, for instance, can be solved within 1-5 minute, SPAMers can buy several computers to solve all these puzzles and go on sending SPAM.
  
  
  
• There is another method but still not widely spread. It implies hiding e-mail address from SPAM programs which dig it up from web-sites. Your e-mail address will be displayed as an image not allowed to be copied and pasted into the address line. The main disadvantage of this methods is that each user will have to type your e-mail address manually, it is quite uncomfortable. That is why this method is not so widely used. At this stage SPAM cannot break this barrier and maybe they do not try to do it because a few site use this method to prevent their e-mail address from be taken to database of SPAMers.
  
  
• There is also a method of requesting the sender a small fee for allowance of his letter, just some cents. If the sender is SPAMer for sure he/ she will not pay you anything or he/ she will use his account with little money on it. In this case the banking systems should be adjusted to control these processes. The requests of this type turn SPAMers expenses to be high while expenses of common senders are fairly low. This method has lots of disadvantages, as it is not worked out yet. Fee requesting is also quite difficult to perform as assistance of banking systems is required. Using this system also presupposes that the accounting record is to be blocked immediately after letter sending in order not to allow the sender to dispatch millions of letter having only one or two dollars on balance. Then it means that some additional operations have to be performed and this leads to additional expenses.
  
  
• Another offered method implies request sending but the only difference is that the character of this request is defined by the sender himself. Before sending the letter one has to perform calculation or apply a document for the taken payment. This allows to avoid expenses for sending requests forth and back but at the same time it forces senders to perform unnecessary calculations. This method is obviously uncomfortable as in case you performed wrong calculations and sent your letter you will never know that your letter was declined.
  
  
• In one of the largest Anti-SPAM companies Brightmail (EN), a team of specialists work at analyzing the incoming correspondence and try to build a model of the SPAM letters. They extract general rules of such letters, its composition and content. This is a quite difficult task as should this model be too much general, this leads to mistaking letters and deleting normal messages. But should this model be too much exact, any variations in SPAM letters allow overcome it. Moreover these systems are always a bit behind SPAMers' technologies. To spread the data of this model takes the company Brightmail some minutes, so if SPAMers can change the content of the letter quicker than the specialists check and distribute it, they can easily master these difficulties.