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They've Stolen My AT

Many people place their email addresses on their Web sites or the Web sites they build. Then, as soon as the site is uploaded to the Internet, their email boxes are flooded with spam. How can you stop this? Try creating a link to your email address.

A common way to make a link to your email address is using the <a> tag:

for example:

When pressing this link, the email client software is opened with your email address in the form field. This is correct if the surfer is using an email client software such as Outlook or Eudora.

When people use Web mail such as gmail or hotmail, clicking a link to an email is useless. For those users, you must provide a different kind of a link to your email:

for example:

The Web mail users cannot USE the link, but they can see your email address, which they can copy and paste or write and type into their Web mail interface.

Specialized software called "spiders" scans the Web pages that are stored on a company's servers. The spiders are also known as "crawlers" or "knowledge-bots" or just "knowbots." Spiders surf the Internet. They are sent out by search engines such as Google, Yahoo, or MSN. Their job is to update the databases of the specific search engines that send them out.

Want a surprise? If you have Web pages that include your email address, then use your favorite search engine to do a search on your email address. The results may surprise you.

There Are Different Types of Spiders

As we've discussed, one type of spider is used to update search engine databases. Another type is used by people who are interested in collecting and using email addresses for their own purposes. These people use spiders to harvest email addresses from Web pages so they can send out advertisements or viruses or anything else that you don't want to the addresses they collect. These spider programs are called "spam bots," and the people who send them out are called "spammers." Spam bots scan Web pages exactly like the search engine spiders do, except that they look for the @ mark, or the source code "mailto:" that is used when constructing an email link.

What Does a Spider See on My Site?

Spiders don't see Web pages like you do. You see a picture of a page that is "rendered" or built by your browser. The behind-the-scenes building blocks used to create a Web page is called "source code" or "HTML code." The spider sees only the source code.

Here's an example. Let's assume that the following appears in the source code of a Web page:

This is the source code to display an image file named "imageFile.jpg". Your browser reads the source code, accesses the image file, and then shows it on screen. The spider, on the other hand, only reads the source code. It doesn't try to access the actual image file. The spider sees only:

In another example, the following appears in the source code:

When you use your browser, you see the text Welcome written in green letters: Welcome

The spider, on the other hand, doesn't see any colors. All it sees is the source code.

The source code for an email link on an HTML page looks like this:

or perhaps like this:

Because HTML pages are plain text, it is easy for spiders to extract email addresses. A spider looks first for either the @ sign or the phrase "mailto:". Once the spider recognizes either of these items, it easily figures out the email address that is part of the source code. Therefore, never write your email address as part of the source code. Do not write it as a part of the src property, as a content, in the <title> tag, or in the title property. Make sure that your Web page does not contain your email address, and you will get less spam.

But, what if you still want your email address to appear on your Web page, in spite of the above? How can you prevent spiders from recognizing that it's an email address?

Use ONE of the following methods to hide the following email address: joe@hotmail.com from the spiders.

Anti-spam Method No. 1: Add Text to the email Address

Example:

Clearly the address "REMOVETHISjoe@hotmail.com" doesn't exist. In order for the address to be valid and useful, the user must erase the text REMOVETHIS, which is easy.

But if everyone in the world adds REMOVETHIS, then the spiders will start to understand what is going on. To prevent this, use a variety of different phrases, for example:

Another possibility:

Anti-spam Method No. 2: Use Decimal Internet-safe Characters

The following table shows that the decimal values of the characters a to z are from 97 to 122.

Example: using decimal equivalents, change the source code from:

to

The user will see Send an email in the browser window. When putting the cursor over the link, the email address can be viewed in the status bar.

As you can see, there is a mixture of regular and ASCII characters. When the user clicks on the link, everything will work fine. However, if users want to see the source code, they will find two surprises:/p>

1. They will not find the @ sign.
2. Special efforts will be required to decipher the code.

If the spider has the decimal/character conversion tables, then the effort to hide the address may be useless.

Anti-spam Method No. 3: Use Hexadecimal Internet-safe Characters

The following table shows that the hexadecimal values of the characters a to z are between 61HEX and 7aHEX

Example: using hexadecimal equivalents of characters, change the source code from:

to

Users will see Send an email in the browser window. When putting the cursor over the link, they will see the email address in the status bar.

When clicking on the link, everything will work fine. But, if the users want to see the source code, they will find two surprises:

1. They will not find the @ sign.
2. They will have difficulties in translating the hexadecimal numbers into English letters.

If the spider has hexadecimal conversion tables, then the effort will have been useless.

Anti-spam Method No. 4: Use an Image of the email Link

Example:

Similar images of email addresses can be generated at the Digital Colony

If you are worried that the spider will be able to convert the image into text by using Optical Character Recognition (OCR) software, then check out this image.

It is doubtful that this image could be converted to text by OCR software.

Creating such an image takes time and effort. Only a human eye and a human mind can discern the email address that is hidden in the graphic.

What is the source code for this image?

That's the whole source code. Do NOT "wrap" the image with <a href="mailto:...> </a>. If you still want the image to be a link to your email address, read method no. 5.

Anti-spam Method No. 5: Use a Program to Hide the email Address

Here is a JavaScript example:

The script needs to be inserted in the Web page at exactly the spot on the page that you wish to have an email link.

If you want your email address to appear but not be hot linked, then use the following code.

The script can be improved by using encryption. But, again, if the spider is capable of running JavaScript, the encryption will be of no value.

If users ask to see the source code, they will have to locate the @ sign and then figure out the email address. This is not an easy task.

Anti-spam Method No. 6: Combine Methods No. 4 and No. 5

Example:

After you have written the JavaScript, insert it into the Web page at exactly the place on the page where you wish to have an email link.

If you only want the address to appear without being hot linked, then use method no. 4 alone.

Anti-spam Method No. 7: Combine Data

The source code looks like this:

The text file, bla.vdr, looks like this:

Explanation: Why did I use the ending .vdr for the text file? The reason is to lower the possibility that the spider will check that particular file. The extension .vdr is my own invention. Any other extension would work just as well. Most importantly, the extension should not be commonly known. Don't use extensions such as .pdf, .doc, or .txt that the spider might recognize and scan.

Users who want to see the source code will have two surprises:

1. They won't find the @ sign.
2. They will have to invest massive efforts to understand how the script connects to the text file with the .vdr ending.

Summary

Spammers use spiders to harvest email addresses from the source code that make up HTML pages.

There are a number of methods that you can use to protect your address from being harvested by spiders.

We have defined seven different anti-spam methods.

There are two main considerations in choosing an anti-spam method:

1. How effectively will the anti-spam method protect the email address against spiders?
2. Will the chosen anti-spam method make it harder or easier for a user to use the email link that appears on the Web page?

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About the author

Zohar Amihud has written a book on how to create a web site and has contributed to the writing of other books including HTML, JavaScript, ASP, ASP.NET, Visual Basic, C# and Microsoft Office. Zohar holds an MCP (Microsoft Certified Professional) certification and a Master's degree in Business Administration specializing in Marketing & Information Technology. When he's not writing, Zohar is probably in the fitness club doing spinning, weight training or running a treadmill.
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