Email spam

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An email box folder filled with spam messages. Spammed-mail-folder.png
An email box folder filled with spam messages.

Email spam, also referred to as junk email, is unsolicited messages sent in bulk by email (spamming).

Contents

The name comes from Spam luncheon meat by way of a Monty Python sketch in which Spam is ubiquitous, unavoidable, and repetitive. [1] Email spam has steadily grown since the early 1990s, and by 2014 was estimated to account for around 90% of total email traffic. [2]

Since the expense of the spam is borne mostly by the recipient, [3] it is effectively postage due advertising. This makes it an excellent example of a negative externality. [4]

The legal definition and status of spam varies from one jurisdiction to another, but nowhere have laws and lawsuits been particularly successful in stemming spam.

Most email spam messages are commercial in nature. Whether commercial or not, many are not only annoying, but also dangerous because they may contain links that lead to phishing web sites or sites that are hosting malware - or include malware as file attachments.

Spammers collect email addresses from chat rooms, websites, customer lists, newsgroups, and viruses that harvest users' address books. These collected email addresses are sometimes also sold to other spammers.

Overview

At the beginning of the Internet (the ARPANET), sending of commercial email was prohibited. [5] Gary Thuerk sent the first email spam message in 1978 to 600 people. He was reprimanded and told not to do it again. [6] Now the ban on spam is enforced by the Terms of Service/Acceptable Use Policy (ToS/AUP) of internet service providers (ISPs) and peer pressure.

Spam is sent by both reputable organizations and lesser companies. When spam is sent by reputable companies it is sometimes referred to as Mainsleaze. [7] [8] Mainsleaze makes up approximately 3% of the spam sent over the internet. [9] The problem with mainsleaze is that it is generally mixed in with mail that the recipients asked for, and it is difficult to tell the difference using traditional mail filters. As a result, if a mail system filters out all the mail from a mainsleazer, they will get complaints from the people who signed up. [7]

It was estimated in 2009 that spam cost businesses around US$130 billion. [10] As the scale of the spam problem has grown, ISPs and the public have turned to government for relief from spam, which has failed to materialize. [11]

Spamvertised sites

Many spam emails contain URLs to a website or websites. According to a Cyberoam report in 2014, there are an average of 54 billion spam messages sent every day. "Pharmaceutical products (Viagra and the like) jumped up 45% from last quarter’s analysis, leading this quarter’s spam pack. Emails purporting to offer jobs with fast, easy cash come in at number two, accounting for approximately 15% of all spam email. And, rounding off at number three are spam emails about diet products (such as Garcinia gummi-gutta or Garcinia Cambogia), accounting for approximately 1%." [12]

Spam is also a medium for fraudsters to scam users into entering personal information on fake Web sites using emails forged to look like they are from banks or other organizations, such as PayPal. This is known as phishing . Targeted phishing, where known information about the recipient is used to create forged emails, is known as spear-phishing. [13]

Spam techniques

Appending

If a marketer has one database containing names, addresses, and telephone numbers of customers, they can pay to have their database matched against an external database containing email addresses. The company then has the means to send email to people who have not requested email, which may include people who have deliberately withheld their email address. [14]

Image spam

Image spam, or image-based spam, [15] [16] is an obfuscation method by which text of the message is stored as a GIF or JPEG image and displayed in the email. This prevents text-based spam filters from detecting and blocking spam messages. Image spam was reportedly used in the mid-2000s to advertise "pump and dump" stocks. [17]

Often, image spam contains nonsensical, computer-generated text which simply annoys the reader. However, new technology in some programs tries to read the images by attempting to find text in these images. These programs are not very accurate, and sometimes filter out innocent images of products, such as a box that has words on it.

A newer technique, however, is to use an animated GIF image that does not contain clear text in its initial frame, or to contort the shapes of letters in the image (as in CAPTCHA) to avoid detection by optical character recognition tools.

Blank spam

Blank spam is spam lacking a payload advertisement. Often the message body is missing altogether, as well as the subject line. Still, it fits the definition of spam because of its nature as bulk and unsolicited email. [18]

Blank spam may be originated in different ways, either intentional or unintentionally:

  1. Blank spam can have been sent in a directory harvest attack, a form of dictionary attack for gathering valid addresses from an email service provider. Since the goal in such an attack is to use the bounces to separate invalid addresses from the valid ones, spammers may dispense with most elements of the header and the entire message body, and still accomplish their goals.
  2. Blank spam may also occur when a spammer forgets or otherwise fails to add the payload when he or she sets up the spam run.
  3. Often blank spam headers appear truncated, suggesting that computer glitches, such as software bugs or other may have contributed to this problem—from poorly written spam software to malfunctioning relay servers, or any problems that may truncate header lines from the message body.
  4. Some spam may appear to be blank when in fact it is not. An example of this is the VBS.Davinia.B email worm [19] which propagates through messages that have no subject line and appears blank, when in fact it uses HTML code to download other files.

Backscatter spam

Backscatter is a side-effect of email spam, viruses, and worms. It happens when email servers are misconfigured to send a bogus bounce message to the envelope sender when rejecting or quarantining email (rather than simply rejecting the attempt to send the message).

If the sender's address was forged, then the bounce may go to an innocent party. Since these messages were not solicited by the recipients, are substantially similar to each other, and are delivered in bulk quantities, they qualify as unsolicited bulk email or spam. As such, systems that generate email backscatter can end up being listed on various DNSBLs and be in violation of internet service providers' Terms of Service.

If an individual or organisation can identify harm done to them by spam, and identify who sent it; then they may be able to sue for a legal remedy, e.g. on the basis of trespass to chattels. A number of large civil settlements have been won in this way, [20] although others have been mostly unsuccessful in collecting damages. [21] [22]

Criminal prosecution of spammers under fraud or computer crime statutes is also common, particularly if they illegally accessed other computers to create botnets, or the emails were phishing or other forms of criminal fraud. [23] [24] [25] [26]

Finally, in most countries specific legislation is in place to make certain forms of spamming a criminal offence, as outlined below:

European Union

Article 13 of the European Union Directive on Privacy and Electronic Communications (2002/58/EC) provides that the EU member states shall take appropriate measures to ensure that unsolicited communications for the purposes of direct marketing are not allowed either without the consent of the subscribers concerned or in respect of subscribers who do not wish to receive these communications, the choice between these options to be determined by national legislation.

In the United Kingdom, for example, unsolicited emails cannot be sent to an individual subscriber unless prior permission has been obtained or unless there is a pre-existing commercial relationship between the parties. [27] [28]

Canada

The Fighting Internet and Wireless Spam Act [29] to fight spam. [30]

Australia

The Spam Act 2003, which covers some types of email and phone spam. [31] Penalties are up to 10,000 penalty units, or 2,000 penalty units for a person other than a body corporate.

United States

In the United States, many states enacted anti-spam laws during the late 1990s and early 2000s. All of these were subsequently superseded by the CAN-SPAM Act of 2003, [32] which was in many cases less restrictive; and any further potential state laws preempted. However, CAN-SPAM leaves intact [33] laws not specific to e-mail. Courts have ruled that spam is, e.g., Trespass to Chattel. [34]

Bulk commercial email does not violate CAN-SPAM, provided that it meets certain criteria, e.g., a truthful subject line, no forged information in the headers. If it fails to comply with any of these requirements it is illegal. Those opposing spam greeted the new law with dismay and disappointment, almost immediately dubbing it the "You Can Spam" Act. [35] [36]

In practice, it had a little positive impact. In 2004, less than one percent of spam complied with CAN-SPAM, [37] although a 2005 review by the Federal Trade Commission claimed that the amount of sexually explicit spam had significantly decreased since 2003 and the total volume had begun to level off. [38] Many other observers viewed it as having failed, [39] [40] although there have been several high-profile prosecutions. [41] [42]

Deception and fraud

Spammers may engage in deliberate fraud to send out their messages. Spammers often use false names, addresses, phone numbers, and other contact information to set up "disposable" accounts at various Internet service providers. They also often use falsified or stolen credit card numbers to pay for these accounts. This allows them to move quickly from one account to the next as the host ISPs discover and shut down each one.

Senders may go to great lengths to conceal the origin of their messages. Large companies may hire another firm to send their messages so that complaints or blocking of email falls on a third party. Others engage in spoofing of email addresses (much easier than IP address spoofing). The email protocol (SMTP) has no authentication by default, so the spammer can pretend to originate a message apparently from any email address. To prevent this, some ISPs and domains require the use of SMTP-AUTH, allowing positive identification of the specific account from which an email originates.

Senders cannot completely spoof email delivery chains (the 'Received' header), since the receiving mailserver records the actual connection from the last mailserver's IP address. To counter this, some spammers forge additional delivery headers to make it appear as if the email had previously traversed many legitimate servers.

Spoofing can have serious consequences for legitimate email users. Not only can their email inboxes get clogged up with "undeliverable" emails in addition to volumes of spam, but they can mistakenly be identified as a spammer. Not only may they receive irate email from spam victims, but (if spam victims report the email address owner to the ISP, for example) a naive ISP may terminate their service for spamming.

Theft of service

Spammers frequently seek out and make use of vulnerable third-party systems such as open mail relays and open proxy servers. SMTP forwards mail from one server to another—mail servers that ISPs run commonly require some form of authentication to ensure that the user is a customer of that ISP.

Increasingly, spammers use networks of malware-infected PCs (zombies) to send their spam. Zombie networks are also known as botnets (such zombifying malware is known as a bot, short for robot). In June 2006, an estimated 80 percent of email spam was sent by zombie PCs, an increase of 30 percent from the prior year. An estimated 55 billion email spam were sent each day in June 2006, an increase of 25 billion per day from June 2005. [43]

For the first quarter of 2010, an estimated 305,000 newly activated zombie PCs were brought online each day for malicious activity. This number is slightly lower than the 312,000 of the fourth quarter of 2009. [44]

Brazil produced the most zombies in the first quarter of 2010. Brazil was the source of 20 percent of all zombies, which is down from 14 percent from the fourth quarter of 2009. India had 10 percent, with Vietnam at 8 percent, and the Russian Federation at 7 percent. [44]

Side effects

To combat the problems posed by botnets, open relays, and proxy servers, many email server administrators pre-emptively block dynamic IP ranges and impose stringent requirements on other servers wishing to deliver mail. Forward-confirmed reverse DNS must be correctly set for the outgoing mail server and large swaths of IP addresses are blocked, sometimes pre-emptively, to prevent spam. These measures can pose problems for those wanting to run a small email server off an inexpensive domestic connection. Blacklisting of IP ranges due to spam emanating from them also causes problems for legitimate email servers in the same IP range.

Statistics and estimates

The total volume of email spam has been consistently growing, but in 2011 the trend seemed to reverse. [45] [46] The amount of spam that users see in their mailboxes is only a portion of total spam sent, since spammers' lists often contain a large percentage of invalid addresses and many spam filters simply delete or reject "obvious spam".

The first known spam email, advertising a DEC product presentation, was sent in 1978 by Gary Thuerk to 600 addresses, the total number of users on ARPANET was 2600 at the time though software limitations meant only slightly more than half of the intended recipients actually received it. [47] As of August 2010, the number of spam messages sent per day was estimated to be around 200 billion. [48] More than 97% of all emails sent over the Internet in 2008 were unwanted, according to a Microsoft security report. [49] MAAWG estimates that 85% of incoming mail is "abusive email", as of the second half of 2007. The sample size for the MAAWG's study was over 100 million mailboxes. [50] [51] [52] In 2018 with growing affiliation networks & email frauds worldwide about 90% of global email traffic is spam as per IPwarmup.com study, which also effects legitimate email senders to achieve inbox delivery. [53]

A 2010 survey of US and European email users showed that 46% of the respondents had opened spam messages, although only 11% had clicked on a link. [54]

Highest amount of spam received

According to Steve Ballmer in 2004, Microsoft founder Bill Gates receives four million emails per year, most of them spam. [55] This was originally incorrectly reported as "per day". [56]

At the same time Jef Poskanzer, owner of the domain name acme.com, was receiving over one million spam emails per day. [57]

Cost of spam

A 2004 survey estimated that lost productivity costs Internet users in the United States $21.58 billion annually, while another reported the cost at $17 billion, up from $11 billion in 2003. In 2004, the worldwide productivity cost of spam has been estimated to be $50 billion in 2005. [58]

Origin of spam

E-mail spam relayed by country in Q2 2007 (% of total) [59]
CountryPercentage
United States
19.6
EU (Top 5)
17.9
China (+ Hong Kong)
8.4
South Korea
6.5
Poland
4.8
Germany
4.2
Brazil
4.1
France
3.3
Russia
3.1
Turkey
2.9
United Kingdom
2.8
Italy
2.8
India
2.5

Because of the international nature of spam, the spammer, the hijacked spam-sending computer, the spamvertised server, and the user target of the spam are all often located in different countries. As much as 80% of spam received by Internet users in North America and Europe can be traced to fewer than 200 spammers. [60]

In terms of volume of spam: According to Sophos, the major sources of spam in the fourth quarter of 2008 (October to December) were:[ unreliable source? ] [13] [61] [62] [63] [64] [65] [66] [67] [68] [69]

When grouped by continents, spam comes mostly from:

In terms of number of IP addresses: the Spamhaus Project ranks the top three as the United States, China, and Russia, [70] followed by Japan, Canada, and South Korea.

In terms of networks:As of 5 June 2007, the three networks hosting the most spammers are Verizon, AT&T, and VSNL International. [70] Verizon inherited many of these spam sources from its acquisition of MCI, specifically through the UUNet subsidiary of MCI, which Verizon subsequently renamed Verizon Business.

Anti-spam techniques

The U.S. Department of Energy Computer Incident Advisory Capability (CIAC) has provided specific countermeasures against email spamming. [71]

Some popular methods for filtering and refusing spam include email filtering based on the content of the email, DNS-based blackhole lists (DNSBL), greylisting, spamtraps, enforcing technical requirements of email (SMTP), checksumming systems to detect bulk email, and by putting some sort of cost on the sender via a proof-of-work system or a micropayment. Each method has strengths and weaknesses and each is controversial because of its weaknesses. For example, one company's offer to "[remove] some spamtrap and honeypot addresses" from email lists defeats the ability for those methods to identify spammers.

Outbound spam protection combines many of the techniques to scan messages exiting out of a service provider's network, identify spam, and taking action such as blocking the message or shutting off the source of the message.

Email authentication to prevent "From:" address spoofing became popular in the 2010s.

Methods of spammers

Gathering of addresses

In order to send spam, spammers need to obtain the email addresses of the intended recipients. To this end, both spammers themselves and list merchants gather huge lists of potential email addresses. Since spam is, by definition, unsolicited, this address harvesting is done without the consent (and sometimes against the expressed will) of the address owners. A single spam run may target tens of millions of possible addresses – many of which are invalid, malformed, or undeliverable.

Obfuscating message content

Many spam-filtering techniques work by searching for patterns in the headers or bodies of messages. For instance, a user may decide that all email they receive with the word "Viagra" in the subject line is spam, and instruct their mail program to automatically delete all such messages. To defeat such filters, the spammer may intentionally misspell commonly filtered words or insert other characters, often in a style similar to leetspeak, as in the following examples: V1agra, Via'gra, Vi@graa, vi*gra, \/iagra. This also allows for many different ways to express a given word, making identifying them all more difficult for filter software.

The principle of this method is to leave the word readable to humans (who can easily recognize the intended word for such misspellings), but not likely to be recognized by a computer program. This is only somewhat effective, because modern filter patterns have been designed to recognize blacklisted terms in the various iterations of misspelling. Other filters target the actual obfuscation methods, such as the non-standard use of punctuation or numerals into unusual places. Similarly, HTML-based email gives the spammer more tools to obfuscate text. Inserting HTML comments between letters can foil some filters. Another common ploy involves presenting the text as an image, which is either sent along or loaded from a remote server.

Defeating Bayesian filters

As Bayesian filtering has become popular as a spam-filtering technique, spammers have started using methods to weaken it. To a rough approximation, Bayesian filters rely on word probabilities. If a message contains many words that are used only in spam, and few that are never used in spam, it is likely to be spam. To weaken Bayesian filters, some spammers, alongside the sales pitch, now include lines of irrelevant, random words, in a technique known as Bayesian poisoning.

Spam-support services

A number of other online activities and business practices are considered by anti-spam activists to be connected to spamming. These are sometimes termed spam-support services: business services, other than the actual sending of spam itself, which permit the spammer to continue operating. Spam-support services can include processing orders for goods advertised in spam, hosting Web sites or DNS records referenced in spam messages, or a number of specific services as follows:

Some Internet hosting firms advertise bulk-friendly or bulletproof hosting. This means that, unlike most ISPs, they will not terminate a customer for spamming. These hosting firms operate as clients of larger ISPs, and many have eventually been taken offline by these larger ISPs as a result of complaints regarding spam activity. Thus, while a firm may advertise bulletproof hosting, it is ultimately unable to deliver without the connivance of its upstream ISP. However, some spammers have managed to get what is called a pink contract (see below) – a contract with the ISP that allows them to spam without being disconnected.

A few companies produce spamware , or software designed for spammers. Spamware varies widely, but may include the ability to import thousands of addresses, to generate random addresses, to insert fraudulent headers into messages, to use dozens or hundreds of mail servers simultaneously, and to make use of open relays. The sale of spamware is illegal in eight U.S. states. [72] [73] [74]

So-called millions CDs are commonly advertised in spam. These are CD-ROMs purportedly containing lists of email addresses, for use in sending spam to these addresses. Such lists are also sold directly online, frequently with the false claim that the owners of the listed addresses have requested (or "opted in") to be included. Such lists often contain invalid addresses. In recent years, these have fallen almost entirely out of use due to the low quality email addresses available on them, and because some email lists exceed 20GB in size. The amount you can fit on a CD is no longer substantial.

A number of DNS blacklists (DNSBLs), including the MAPS RBL, Spamhaus SBL, SORBS and SPEWS, target the providers of spam-support services as well as spammers. DNSBLs blacklist IPs or ranges of IPs to persuade ISPs to terminate services with known customers who are spammers or resell to spammers.

Unsolicited bulk email (UBE)
A synonym for email spam.
Unsolicited commercial email (UCE)
Spam promoting a commercial service or product. This is the most common type of spam, but it excludes spams that are hoaxes (e.g. virus warnings), political advocacy, religious messages, and chain letters sent by a person to many other people. The term UCE may be most common in the USA. [75]
Pink contract
A pink contract is a service contract offered by an ISP which offers bulk email service to spamming clients, in violation of that ISP's publicly posted acceptable use policy.
Spamvertising
Spamvertising is advertising through the medium of spam.
Opt-in, confirmed opt-in, double opt-in, opt-out
Opt-in, confirmed opt-in, double opt-in, opt-out refers to whether the people on a mailing list are given the option to be put in, or taken out, of the list. Confirmation (and "double", in marketing speak) refers to an email address transmitted e.g. through a web form being confirmed to actually request joining a mailing list, instead of being added to the list without verification.
Final, Ultimate Solution for the Spam Problem (FUSSP)
An ironic reference to naive developers who believe they have invented the perfect spam filter, which will stop all spam from reaching users' inboxes while deleting no legitimate email accidentally. [76] [77]

History

See also

Notes

    Related Research Articles

    Email Method of exchanging digital messages between people over a network

    Electronic mail is a method of exchanging messages ("mail") between people using electronic devices. Email entered limited use in the 1960s, but users could only send to users of the same computer, and some early email systems required the author and the recipient to both be online simultaneously, similar to instant messaging. Ray Tomlinson is credited as the inventor of email; in 1971, he developed the first system able to send mail between users on different hosts across the ARPANET, using the @ sign to link the user name with a destination server. By the mid-1970s, this was the form recognized as email.

    Spamming Unsolicited electronic messages, especially advertisements

    Spamming is the use of messaging systems to send an unsolicited message (spam), especially advertising, as well as sending messages repeatedly on the same website. While the most widely recognized form of spam is email spam, the term is applied to similar abuses in other media: instant messaging spam, Usenet newsgroup spam, Web search engine spam, spam in blogs, wiki spam, online classified ads spam, mobile phone messaging spam, Internet forum spam, junk fax transmissions, social spam, spam mobile apps, television advertising and file sharing spam. It is named after Spam, a luncheon meat, by way of a Monty Python sketch about a restaurant that has Spam in almost every dish and where vikings annoyingly sing "Spam" over and over again.

    Open mail relay

    An open mail relay is a Simple Mail Transfer Protocol (SMTP) server configured in such a way that it allows anyone on the Internet to send e-mail through it, not just mail destined to or originating from known users. This used to be the default configuration in many mail servers; indeed, it was the way the Internet was initially set up, but open mail relays have become unpopular because of their exploitation by spammers and worms. Many relays were closed, or were placed on blacklists by other servers.

    A Domain Name System-based Blackhole List (DNSBL) or Real-time Blackhole List (RBL) is an effort to stop email spamming. It is a "blacklist" of locations on the Internet reputed to send email spam. The locations consist of IP addresses which are most often used to publish the addresses of computers or networks linked to spamming; most mail server software can be configured to reject or flag messages which have been sent from a site listed on one or more such lists. The term "Blackhole List" is sometimes interchanged with the term "blacklist" and "blocklist".

    Whitelisting is the practice of explicitly allowing some identified entities access to a particular privilege, service, mobility, access or recognition. It is the reverse of blacklisting.

    Various anti-spam techniques are used to prevent email spam.

    CAN-SPAM Act of 2003

    The Controlling the Assault of Non-Solicited Pornography And Marketing (CAN-SPAM) Act of 2003, signed into law by President George W. Bush on December 16, 2003, established the United States' first national standards for the sending of commercial e-mail and requires the Federal Trade Commission (FTC) to enforce its provisions.

    Address munging is the practice of disguising an e-mail address to prevent it from being automatically collected by unsolicited bulk e-mail providers. Address munging is intended to disguise an e-mail address in a way that prevents computer software from seeing the real address, or even any address at all, but still allows a human reader to reconstruct the original and contact the author: an email address such as, "no-one@example.com", becomes "no-one at example dot com", for instance.

    A joe job is a spamming technique that sends out unsolicited e-mails using spoofed sender data. Early joe jobs aimed at tarnishing the reputation of the apparent sender or inducing the recipients to take action against them, but they are now typically used by commercial spammers to conceal the true origin of their messages and to trick recipients into opening emails apparently coming from a trusted source.

    A bounce message or just "bounce" is an automated message from an email system, informing the sender of a previous message that message had not been delivered. The original message is said to have "bounced". More formal terms for bounce message include "Non-Delivery Report" or "Non-Delivery Receipt" (NDR), [Failed] "Delivery Status Notification" (DSN) message, or a "Non-Delivery Notification" (NDN).

    The Spamhaus Project organization

    The Spamhaus Project is an international organisation, based in both London and Geneva, founded in 1998 by Steve Linford to track email spammers and spam-related activity. The name spamhaus, a pseudo-German expression, was coined by Linford to refer to an Internet service provider, or other firm, which spams or knowingly provides service to spammers.

    Email filtering is the processing of email to organize it according to specified criteria. The term can apply to the intervention of human intelligence, but most often refers to the automatic processing of incoming messages with anti-spam techniques - to outgoing emails as well as those being received.

    Message submission agent computer program or software agent that receives electronic mail messages

    A message submission agent (MSA) or mail submission agent is a computer program or software agent that receives electronic mail messages from a mail user agent (MUA) and cooperates with a mail transfer agent (MTA) for delivery of the mail. It uses ESMTP, a variant of the Simple Mail Transfer Protocol (SMTP), as specified in RFC 6409.

    Spamware is software designed by or for spammers. Spamware varies widely, but may include the ability to import thousands of addresses, to generate random addresses, to insert fraudulent headers into messages, to use dozens or hundreds of mail servers simultaneously, and to make use of open relays. Being an automated software it can create e-mail broadcasting hub by establishing superiority in numbers and sending capability as well as brings a position of great disturbance to its target. Normally, applications can be found in various online based chat rooms like Nimbuzz. The sale of spamware is illegal in eight U.S. states.

    Email harvesting is the process of obtaining lists of email addresses using various methods. Typically these are then used for bulk email or spam.

    A challenge–response system is a type of spam filter that automatically sends a reply with a challenge to the (alleged) sender of an incoming e-mail. It was originally designed in 1997 by Stan Weatherby, and was called Email Verification. In this reply, the sender is asked to perform some action to assure delivery of the original message, which would otherwise not be delivered. The action to perform typically takes relatively little effort to do once, but great effort to perform in large numbers. This effectively filters out spammers. Challenge–response systems only need to send challenges to unknown senders. Senders that have previously performed the challenging action, or who have previously been sent e-mail(s) to, would be automatically whitelisted.

    The history of email spam reaches back to the mid-1990s when commercial use of the internet first became possible - and marketers and publicists began to test what was possible.

    Since Internet users and system administrators have deployed a vast array of techniques to block, filter, or otherwise banish spam from users' mailboxes and almost all Internet service providers forbid the use of their services to send spam or to operate spam-support services, special techniques are employed to deliver spam emails. Both commercial firms and volunteers run subscriber services dedicated to blocking or filtering spam.

    People tend to be much less bothered by spam slipping through filters into their mail box, than having desired e-mail ("ham") blocked. Trying to balance false negatives vs false positives is critical for a successful anti-spam system. As servers are not able to block all spam there are some tools for individual users to help control over this balance.

    A cold email is an unsolicited e-mail that is sent to a receiver without prior contact. It could also be defined as the email equivalent of cold calling. Cold emailing is a subset of email marketing and differs from transactional and warm emailing.

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    Further reading

    Spam info

    Spam reports

    Government reports and industry white papers