If you are an email user, chances are you’ve experienced the aggravation and decreased productivity associated with spam email. But are you aware that spam email that reaches your inbox can have potentially serious consequences for you and your business?

 Spam email, or junk email, refers to unsolicited messages sent in bulk. This notorious email threat got its name from Spam lunch meat, which has a reputation of being ubiquitous, repetitive and unavoidable. According to Statista, spam messages accounted for an alarming 56% of email traffic in March 2019. Although statistics show that spammers only receive one reply for every 12,500,000 emails sent, spam email remains a profitable business model due to the astronomically large number of phony messages sent per day.

The majority of spam email is commercial in nature, and since the expense of a phony message is borne mainly by the recipient, spam can be viewed as postage due advertising.

Regardless of its purpose or origin, spam email should be recognized as a serious threat. Aside from the fact that it is extremely annoying, spam may contain malicious links or attachments and is often a vector for other serious attacks like phishing and malware.

History of Spam Email

Although the first spam email was sent in 1978 to several hundred users on ARPANET, email spam emerged as a serious problem in the 1990s when commercial use of the Internet became possible. As the Internet gained popularity, spam email became increasingly unavoidable and profitable for attackers. Since the early 1990s, the prominence of spam email steadily grew until 2014, at which point it was estimated that spam email accounted for roughly 90% of all email messages sent.

In 1996, anti-spam activists recognized the serious problem that spam email had become, and began taking action to combat it. That year Dave Rand and Paul Vixie, two well-known software engineers, founded the Mail Abuse Prevention System (MAPS). The organization’s mission was to pioneer anti-spam techniques. MAPS collected a list of malicious IP addresses, which became known as the Real-time Blackhole List (RBL), and used this list to block unwanted emails.

In 2001, the SpamAssassin spam-filtering platform was first uploaded to SourceForge by creator Justin Mason. At the time, spam email was becoming increasingly problematic and no real tools existed to effectively combat it. The open-source project, which analyzes and scores emails based on how strongly they resemble either spam or non-spam, experienced rapid growth and evolution in its early years. In 2004, SpamAssassin become an Apache Software Foundation project. Eighteen years later, SpamAssassin is still an extremely popular spam filtration platform, and the framework is a key element of many email security solutions.

Spammers’ Methods

Crafting a spam email campaign is relatively easy and straightforward, and research shows that spam earns senders approximately $7,000 per day. Criminals typically utilize similar methods to bombard users with unsolicited email, which include:

  • Email address harvesting: In order to send out unsolicited emails, spammers must first collect the email addresses of the intended recipients. It is common for them to purchase or trade lists of email addresses from other spammers. In some cases, spammers utilize special software known as "harvesting bots" or "harvesters", which scour the Internet to obtain email addresses from public data. Attackers will sometimes launch directory harvest attacks, in which valid email addresses at a specific domain are found by guessing the email address using common usernames in email addresses at that domain. A final tactic that spammers employ for email address harvesting is offering a product or a service free of charge as long as the user provides a valid email address. Attackers then use these addresses as spam targets for future campaigns.
  • Obfuscating message content: To defeat spam filters that operate by searching for patterns in the subjects or bodies of messages, spammers will often intentionally misspell commonly filtered words or insert other characters to make it more difficult for filter software to identify their messages. These changes are often small and subtle, making spammers’ messages readable to humans but unlikely to be recognized by computer programs.
  • Defeating Bayesian filters: Bayesian filtering, which works by correlating the use of tokens (which are typically words), with spam and non-spam emails and then using Bayes' theorem to calculate the probability that an email is or is not spam, has become a popular spam-filtering technique. Naturally, attackers have developed methods to weaken this type of spam filtering. To defeat Bayesian filters, some spammers now include irrelevant, random words to manipulate word probabilities in a technique known as Bayesian poisoning.
  • Spam-support services: Various online activities and business practices, known as spam-support services, are believed to support spammers’ efforts and allow their operations to continue. Spam-support services include processing orders for goods advertised in spam, hosting Web sites or DNS records referenced in spam messages, bulk-friendly hosting, DNS blacklists and the production of spamware.

How to Recognize Spam Email:

While it is blatantly obvious that certain emails are spam, some spammers craft highly deceptive messages that are difficult to differentiate from legitimate emails. Here are some best practices for identifying spam email that users should engage in to avoid falling from spammers’ dangerous scams:

  • Look for unknown, suspicious or spoofed email addresses. Pay attention to the sender’s email address, especially if a message seems strange or suspicious. Attackers often use spoofed email addresses to deceive recipients. 
  • Be wary of unfamiliar links or strange attachments. Refrain from clicking on links or downloading files in emails unless you trust the source. Malware, viruses, and other types of malicious material can be easily downloaded through malicious attachments or links.
  • Look for misspelled words or added characters within the subject or body of an email. Spammers often intentionally misspell words or insert additional characters within their messages to evade spam filtration software. Be cautious of emails that contain spelling and/or grammatical errors.
  • Think before you respond: watch for offers or opportunities that seem too good to be true. If the content in an email seems too good to be true, it likely is! Such emails are often phishing scams trying to steal credentials or other sensitive information. Remember to never give out personal information such as passwords, social security numbers, or credit card numbers via email. Legitimate businesses will never ask for it, and sharing sensitive data can result in significant losses and, in some cases, identity theft.

If you suspect that a message is phony, don’t forget that replying to spam or attempting to “unsubscribe” comes with its own set of risks! Play it safe and don’t reply at all if you are unsure about an email.

How to Prevent Spam Email from Reaching the Inbox:

While spam filtration technology is an important element of any spam protection strategy, this software is most effective when it is implemented as part of a comprehensive, multi-layered email security gateway solution.

Defense in depth in critical in effectively securing email accounts. No single layer of technology is sufficient in protecting against spam email and other email threats. Look for a comprehensive email security gateway solution with multiple layers of protection which work harmoniously to prevent spam and other types of malicious emails from reaching the inbox.

How Guardian Digital Can Help:

Guardian Digital EnGarde Email Security Gateway, the premier open-source email security gateway solution, provides complete, highly effective protection against spam email and the other dangerous attack variations that constitute today’s email threat landscape. Benefits of securing your business email with EnGarde include:

  • Fully-managed, end-to-end control of your email, preventing malicious messages from reaching the inbox
  • Multi-layered architecture, where individual layers of security work in concert to provide comprehensive, resilient protection
  • Secure endpoint encryption using strong cryptography
  • Multiple leading antivirus engines and spam filtration technologies, including the Apache SpamAssassin scoring framework  
  • Tighter security, adaptive implementation and eliminated risk of vendor lock-in through the use of a transparent, collaborative development approach
  • Centrally managed cloud-based administration
  • Unparalleled 24x7x365 customer support, conveniently providing you with the peace of mind to focus on aspects of running your business other than email security

Want to learn more about spam email and how to protect against it?

Do you have any questions about spam email and spam protection that haven’t been addressed in this article? If so, please contact us and we would love to answer them!

Stay tuned for our next Email Threats Explained blog post: What are Viruses?

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