Security Info
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Spam is unsolicited email, normally with an advertising content sent out as a mass mailing. The term spam is derived from spiced ham, the first tinned meat product that did not need to be kept in a refrigerator. Its use spread as a result, becoming part of the communal meals of the United Status and Russian armies during the Second World War. Later on, in 1969, actors from Monty Python acted out a sketch in which customers in a restaurant tried to choose from a menu where all the dishes contained… spam, while a group of Vikings chanted “spam, spam, spam, lovely spam, wonderful spam”. In short, spam appeared everywhere and drowned out all the other conversations. For historical purposes, the first documented case of spam is a letter sent in 1978 by the company Digital Equipment Corporation. This company sent an advertisement about its DEC-20 computer to all ArpaNet users (precursor of the Internet) on the west coast of the United States. However, the word spam was not coined until 1994, when an advertisement appeared in Usenet from the lawyers Lawrence Cantera and Martha Siegel. It provided information about their service for completing entry forms for United States work permits. This advertisement was sent using a script to all the discussion groups back then. Some of the most common characteristics these types of email messages have are:
Although this type of malware is normally spread via email, there are variants, each with their own name according to their distribution channel:
Spam is a phenomenon which is increasing daily, representing a high percentage of all email traffic. What’s more, as more effective solutions and technologies emerge to tackle spam, spammers (malicious users exclusively devoted to sending spam) become ever more sophisticated and modify their techniques in order to avoid the countermeasures deployed by users. 
Obtaining email addresses Spammers try to obtain as many valid email addresses as possible, i.e. actually used by users. They use different techniques for this, some of which are highly sophisticated:
Consequently, all email users are at risk from these types of attacks. Any address published on the Internet (used in forums, newsgroups or on any website) is more likely to be a spam victim. Techniques used. Spammers use numerous techniques to produce messages capable of by-passing all types of mail filters. Some of the tricks used to obscure the message’s HTML code are looked at below:
Although some of the techniques used have now been mentioned, there are many more, such as the use of incorrect HTML tags, URL encoding, the use of HTML entities to conceal certain letters, the use of invisible ink, etc. Other types of techniques are based on including the spam message as an attached file in a valid message or the use of CSS (Cascading Style Sheets) in spam messages to conceal certain words or parts of the message. Methods used for spam distribution are as follows:
The main damage caused by receiving spam can be classed as direct damage:
And indirect damage, such as:
Spam may also serve as a propagation method for an even greater danger: malware. It may be used to distribute malware that does not have its own means of propagation: Trojans, keyloggers, backdoors etc. In a spam mail, it is very easy to include an attachment with a virus or a link to a site (apparently interesting), from which some type of malicious code is downloaded without the user knowing. Viruses can also be concealed in the message code. The damage caused by spam is extensive, and even more so in a corporate environment where the economic repercussions can be enormous. As a result, it is crucial that legitimate messages reach their destination, while spam must be blocked. It appears obvious that protection against spam, particularly at a corporate level, should be a top priority. This type of malware exists purely for financial reasons. Sending an email message to promote all types of services, products, frauds and swindles is incredibly cheap, with substantial profits being obtained from convincing only a very small percentage of users to buy the product or service.
The mail message filter is a basic measure to prevent spam entering users’ mail boxes. There are many applications that can filter emails by message, keywords, domains, IP addresses from where the messages come from, etc. For companies, rather than simply being able to identify spam messages correctly, the problem depends on adequately managing the large quantities of messages of this type that are received daily. Consequently, the tools to be used should take into account other factors. The best anti-spam systems should be based on more than just one technology. They should use diverse techniques (heuristic rules, Bayesian filters, white and black lists, digital signatures, sender authentication, etc) which achieve the basic aim of reducing false positives to a minimum and therefore eliminate the possibility of a user losing a message as a result of a system error, maintaining a high degree of efficiency in spam detection in the process. Panda Software has a complete range of technological solutions. These solutions are varied and adapted to the needs of each client, from the domestic user to the business environment, offering comprehensive centralized protection for all network layers: workstations, mail and browser servers and corporate firewalls. Also, take into account the following guidelines for protecting yourself against spam and minimizing its effects:
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Spam: Unsolicited email messages 
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