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Cloaking Meta Tags
by Ralph Tegtmeier
(rt) This short tutorial will cover the cloaking of web page meta tags, which follows a different procedure than the IP delivery and full page cloaking method commonly employed for high grade stealthing.
Server Requirements To take advantage of this procedure you must be able to make use of Server Side Includes (SSI) on your web server. Note IIS/4.0 users: The code presented here is an extended SSI expression which is not supported under IIS/4.0.
Meta tag cloaking is effected by excluding browsers from viewing certain parts of a web page, specifically the header where meta tags are positioned by default.
Browsers are determined by their UserAgent variable. Once properly cloaked, it won't make any difference whether you read the source code online or whether you download it for viewing offline – the meta tag code will remain hidden, the browser will not be able to read it and will therefore not download it either.
Browser UserAgents - Here is a list of UserAgents as used by popular web browsers:
- "Lynx": Lynx text browser - "Mozilla": Netscape browsers - "MSIE": Microsoft Internet Explorer - "NCSA Mosaic": Mosaic technology based browsers like Spry, Spyglass, etc. - "Opera": Opera browser - "WebTV" - WebTV's proprietary browser
Activating SSI - The .htaccess File
If your web server is not configured for SSI by default, you will need to upload a file named ".htaccess" (please note the period/dot at the beginning of the file name!) to your server directory. This can be done by Telnet or FTP.
The .htaccess file should have the following content:
- .htaccess entries below this line -
Options Includes +ExecCGI AddType text/x-server-parsed-html .html
- .htaccess entries above this line -
Note that many web servers will not require the specfication "Includes", meaning you can omit it altogether. However, since it won't do any harm to keep it in your file, we suggest you do not change the above entry. Thus, should you switch servers some day, you will not have to readjust your .htaccess file.
After you have uploaded the modified .htaccess file (MUST be in Ascii mode!), you're ready to go.
In the HEADER section of the web page whose meta tags you wish to protect, place the following code:
- First HEADER entry below this line -
<!-# if expr=""$HTTP_USER_AGENT" != /Mozilla|MSIE|Opera|Lynx|WebTV|NCSA Mosaic/" ->
- First HEADER entry above this line -
VERY IMPORTANT (1) = The above should actually be in one SINGLE line! As email clients tend to word wrap lines which are too long for display, we have done their job here for better readability. But make no mistakes: The code above MUST be free from line wraps, or it won't work!
Under this first header entry, you may now add the actual meta tags you wish to protect.
When you are done, you must close the protected section with the last header entry, or the rest of your page won't be displayed either!
- Last HEADER meta tags protection entry below this line -
<!-# endif ->
- Last HEADER meta tags protection entry above this line -
VERY IMPORTANT (2) = If you have other entries in your page header (e.g. for an external CSS style sheet, an external JavaScript applet, etc.) you MUST place these OUTSIDE the protected area (but WITHIN the header tags) or they will not work unless you are operating with a browser sporting a UserAgent not included in the code above.
So what does it do? The SSI code outlined above will determine the accessing browser by its UserAgent variable. If it is recognized, the system will skip the content within the exclusion tags, effectively preventing the meta tags from being displayed.
Search engine spiders not using common browser UserAgent variables (most don't) will still get to read the meta tags nevertheless, which is, of course, what you want them to do.
Limitations The method outlined above may well qualify for "poor man's cloaking" - it is NOT an industrial-strength protection against code snoops, the more so as UserAgents can easily be forged ("spoofed"), but it will cover about 95% of all ordinary browsers and their users without putting an undue strain on server load and, hence, system performance.
Bear in mind, too, that meta tags are gradually losing in importance as many search engines have stopped indexing them because of massive abuse by keyword spamming ("spamdexing") and irrelevant description tags in the past.
Other uses - This technique can also be used to prevent email harvester bots (address extractors) from culling email addresses from textarea fields, e.g. if you happen to display your ezine complete with editors' addresses in text format on your web site.
Further resources - Read more about protecting textarea fields from email harvesters here: < http://fantomaster.com/faarticles0.html#protect-email-addresses >
A more detailed discussion of this method, including some practial demonstrations, can be found on our web site at: < http://fantomaster.com/fasmbacntut01a.html >
Ralph Tegtmeier is the co-founder and principal of fantomaster.com Ltd. (UK) and fantomaster.com GmbH (Belgium), < http://fantomaster.com/ > a company specializing in webmasters software development, industrial-strength cloaking and search engine positioning services. He has been a web marketer since 1994 and is editor-in-chief of fantomNews, a free newsletter focusing on search engine optimization, available at: < http://fantomaster.com/fantomnews-sub.html > You can contact him at mailto:fneditor@fantomaster.com (c) copyright 2001 by fantomaster.com All rights reserved. Downloaded at: < http://fantomaster.com/ >
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