Making email addresses safe from bots on a webpage?

Question

When placing email addresses on a webpage do you place them as text like this:

[email protected]

or use a clever trick to try and fool the email address harvester bots? For example:

HTML Escape Characters:

joe.somebody@company.com

Javascript Decrypter:

function XOR_Crypt(EmailAddress)
{
    Result = new String();
    for (var i = 0; i < EmailAddress.length; i++)
    {
     Result += String.fromCharCode(EmailAddress.charCodeAt(i) ^ 128);
    }
    document.write(Result);
}

XOR_Crypt("êïå®óïíåâïäùÀãïíðáîù®ãïí");

Human Decode:

[email protected]

joe.somebody AT company.com

What do you use or do you even bother?

Answer 1

I generally don't bother. I used to be on a mailing list that got several thousand spams every day. Our spam filter (spamassassin) let maybe 1 or 2 a day through. With filters this good, why make it difficult for legitimate people to contact you?

Answer 2

An image with the text.
If someone wants to contact me bad enough, let him copy the text by hand.

Answer 3

I wouldn't bother -- it is fighting the SPAM war at the wrong level. Particularly for company web sites I think it makes things look very unprofessional if you have anything other than the straight text on the page with a mailto hyperlink.

There is so much spam flying around that you need good filtering anyway, and any bot is going end up understanding all the common tricks anyway.

Answer 4

Try an Email Icon generator. http://services.nexodyne.com/email/

Ofcourse there are still some OCR bots which might get this..

Answer 5

You can protect your email address with reCAPTCHA, they offer a free service so people have to enter a CAPTCHA (Completely Automated Public Turing test to tell Computers and Humans Apart) to see your email: http://mailhide.recaptcha.net/

Answer 6

Invent your own crazy email address obfuscation scheme. Doesn't matter what it is, really, as long as it's not too similar to any of the commonly known methods.

The problem is that there really isn't a good solution to this, they're all either relatively simple to bypass, or rather irritating for the user. If any one method becomes prevalent, then someone will find a way around it.

So rather than looking for the One True email address obfuscation technique, come up with your own. Count on the fact that these bot authors don't care enough about your site to sit around writing a thing to bypass your slightly crazy rendering-text-with-css-and-element-borders or your completely bizarre, easily-cracked javascript encryption. It doesn't matter if it's trivial, nobody will bother trying to bypass it just so they can spam you.

Answer 7

I make mine [email protected] and then next to it I write "Remove the capital letters"

Answer 8

The only safest way is of course not to put the email address onto web page in the first place.

Answer 9

Another, possibly unique, technique might be to use multiple images and a few plain-text letters to display the address. That might confuse the bots.

Answer 10

HTML:

<a href="#" class="--mailto--john--domain--com-- other classes goes here" />

JavaScript, using jQuery:

// match all a-elements with "--mailto--" somehere in the class property
$("a[class*='--mailto--']").each(function ()
{
    /*
    for each of those elements use a regular expression to pull
    out the data you need to construct a valid e-mail adress
    */
    var validEmailAdress = this.className.match();

    $(this).click(function ()
    {
        window.location = validEmailAdress;
    });
});

Answer 11

A script that saves email addresses to png files would be a secure solution ( if you have enough space and you are allowed to embed images in your page )

Answer 12

This is what we use (VB.NET):

Dim rxEmailLink As New Regex("<a\b[^>]*mailto:\b[^>]*>(.*?)</a>")
Dim m As Match = rxEmailLink.Match(Html)
While m.Success
    Dim strEntireLinkOrig As String = m.Value
    Dim strEntireLink As String = strEntireLinkOrig
    strEntireLink = strEntireLink.Replace("'", """") ' replace any single quotes with double quotes to make sure the javascript is well formed
    Dim rxLink As New Regex("(<a\b[^>]*mailto:)([\w.\-_^@]*@[\w.\-_^@]*)(\b[^>]*?)>(.*?)</a>")
    Dim rxLinkMatch As Match = rxLink.Match(strEntireLink)
    Dim strReplace As String = String.Format("<script language=""JavaScript"">document.write('{0}{1}{2}>{3}</a>');</script>", _
                RandomlyChopStringJS(rxLinkMatch.Groups(1).ToString), _
                ConvertToAsciiHex(rxLinkMatch.Groups(2).ToString), _
                rxLinkMatch.Groups(3), _
                ConvertToHtmlEntites(rxLinkMatch.Groups(4).ToString))
    Result = Result.Replace(strEntireLinkOrig, strReplace)
    m = m.NextMatch()
End While

and

    Public Function RandomlyChopStringJS(ByVal s As String) As String
        Dim intChop As Integer = Int(6 * Rnd()) + 1
        Dim intCount As Integer = 0
        RandomlyChopStringJS = ""
        If Not s Is Nothing AndAlso Len(s) > 0 Then
            For Each c As Char In s.ToCharArray()
                If intCount = intChop Then
                    RandomlyChopStringJS &= "'+'"
                    intChop = Int(6 * Rnd()) + 1
                    intCount = 0
                End If
                RandomlyChopStringJS &= c
                intCount += 1
            Next
        End If
    End Function

We override Render and run the outgoing HTML through this before it goes out the door. This renders email addresses that render normally to a browser, but look like this in the source:

<script language="JavaScript">document.write('<a '+'clas'+'s='+'"Mail'+'Link'+'" hr'+'ef'+'="ma'+'ilto:%69%6E%66%6F%40%62%69%63%75%73%61%2E%6F%72%67">&#105;&#110;&#102;&#111;&#64;&#98;&#105;&#99;&#117;&#115;&#97;&#46;&#111;&#114;&#103;</a>');</script>

Obviously not foolproof, but hopefully cuts down on a certain amount of harvesting without making things hard for the visitor.

Answer 13

Use a contact form instead. Put all of your email addresses into a database and create an HTML form (subject, body, from ...) that submits the contents of the email that the user fills out in the form (along with an id or name that is used to lookup that person's email address in your database) to a server side script that then sends an email to the specified person. At no time is the email address exposed. You will probably want to implement some form of CAPTCHA to deter spambots as well.

Answer 14

Put a button on the page that says "Click here to view my Email address" and when it is clicked, display a message box or unscramble some text or whatever.

Answer 15

It depends on what exactly your needs are. For most sites with which I work, I have found it far more useful to put in a "contact me/us" form which sends an email from the system to whomever needs to be contacted. I know that this isn't exactly the solution that you are seeking but it does completely protect against harvesting and so far I have never seen spam sent through a form like that. It will happen but it is very rare and you are never harvested.

This also gives you a chance to log the messages before sending them giving you an extra level of protection against losing a contact, if you so desire.

Answer 16

Gmail which is free has an awesome spam filter.

If you don't want to use Gmail directly you could send the email to gmail and use gmail forwarding to send it back to you after it has gone through their spam filter.

In a more complex situation, when you need to show a @business.com address you could show the [email protected] and have all this mail forwarded to a gmail account who then forwards it back to the [email protected]

I guess it's not a direct solution to your question but it might help. Gmail being free and having such a good SPAM filter makes using it a very wise choice IMHO.

I receive about 100 spam per day in my gmail account but I can't remember the last time one of them got to my inbox.

To sum up, use a good spam filter whether Gmail or another. Having the user retype or modify the email address that is shown is like using DRM to protect against piracy. Putting the burden on the "good" guy shouldn't be the way to go about doing anything. :)

Answer 17

I don't bother. You'll only annoy sophisticated users and confuse unsophisticated users. As others have said, Gmail provides very effective spam filters for a personal/small business domain, and corporate filters are generally also very good.

Answer 18

I've written encoder (source) that uses all kinds of parsing tricks that I could think of (different kinds of HTML entities, URL encoding, comments, multiline attributes, soft hyphens, non-obvious structure of mailto: URL, etc)

It doesn't stop all harvesters, but OTOH it's completely standards-compliant and transparent to the users.

Another IMHO good approach (which you can use in addition to tricky encoding) is along lines of:

<a href="mailto:[email protected]" 
   onclick="this.href=this.href.replace(/hatestogetspam/,'')">

Answer 19

porneL's excellent other approach, on Nov 17 '08 at 21:18, would be even better if the link was completed with an image of the correct address so the user could write it down correctly as well as clicking it. Using the replace like this would still both effectively hide the real address from bots and give the user a clickable address.

Answer 20

For your own email address I'd recommend not worrying about it too much. If you have a need to make your email address available to thousands of users then I would recommend either using a gmail address (vanilla or via google apps) or using a high quality spam filter.

However, when displaying other users email addresses on your website I think some level of due diligence is required. Luckily, a blogger named Silvan Mühlemann has done all the difficult work for you. He tested out different methods of obfuscation over a period of 1.5 years and determined the best ones, most of them involve css or javascript tricks that allow the address to be presented correctly in the browser but will confuse automated scrapers.

Answer 21

Spam bots will have their own Javascript and CSS engines over time, so I think you shouldn't look in this direction.