Robots, Agents and Spiders - Identifying Search Engine Crawlers

If you've been surfing search engine optimization web sites, you've no doubt come across the above being mentioned on many occasions.

Crawlers, Agents, Bots, Robots and Spiders

Five terms all describing basically the same thing, but in this article they'll be referred to collectively as spiders or "agents". A search engine spider is an automated software program used to locate and collect data from web pages for inclusion in a search engine's database and to follow links to find new pages on the World Wide Web. The term "agent" is more commonly applied to web browsers and mirroring software.

If you've ever examined your server logs or web site traffic reports, you've probably come across some weird and wonderful names for search engine spiders, including "Fluffy the Spider" and Slurp. Depending upon the type of web traffic reports you receive, you may find spiders listed in the "Agents" section of your statistics.

Not all spiders are good

Who actually owns these spiders? It's good to know the beneficial from the bad. Some agents are generated by software such as Teleport Pro, an application that allows people to download a full "mirror" of your site onto their hard drives for viewing later on, or sometimes for more insidious purposes such as plagiarism. If you have a large or image heavy site, the practice of web site stripping could also have a serious impact on your bandwidth usage each month.

Banning spiders and agents

If you notice entries like Teleport Pro and WebStripper in your traffic reports, someone's been busy attempting to download your web site. You don't have to just sit back and let this happen. If you are commercially hosted, you'll be able to add a couple of lines to your robots.txt file to prevent repeat offenders from stripping your site.

The robots.txt file gives search engine spiders and agents direction by informing them what directories and files they are allowed to examine and retrieve. These rules are called The Robots Exclusion Standard.

To prevent certain agents and spiders from accessing any part of your web site, simply enter the following lines into the robots.txt file:

User-agent: NameOfAgent
Disallow: /

Ensure that you enter the name of the agent exactly as it appeared in your reports/logs e.g. Teleport Pro/1.29 and that there is a separate entry for each agent. Skip a line between entries. You could do the same to exclude search engine spiders, but somehow I don't think you'll really want to do this :0). The "/" in the above example means disallow access to any directory. You can also disallow access by spiders and agents to certain directories e.g.

User-agent: *
Disallow: /cgi-bin/

In this example the asterisk (wildcard) indicates "all". Don't use the asterisk in the Disallow statement to indicate "all", use the forward slash instead.

If you don't have a robots.txt file, create one in notepad and upload it to the docs directory (or the root of whichever directory your web pages are stored in). Never use a blank robots.txt file as some search engines may see this as an indication that you don't want your site spidered at all! Have at least one entry in the file.

Unfortunately, defining web stripper agents and spiders in your robots.txt file won't work in all cases as some mirroring software applications have the ability to mimic web browser identifiers; but at least it's some protection that may save you some valuable bandwidth.

If you're not able to create a robots.txt file, which is usually the case if you are hosted by a free hosting service, use the robots exclusion meta tag on your pages.