When scraping content from the web don't make it obvious

Torrential Web Dev

Sunday, November 4. 2007

Posted by Jonathan Street in PHP Programming at 18:46

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When scraping content from the web don't make it obvious

A couple of hours ago I was playing around scraping some content from a website. All was going well until suddenly I couldn't get my script to fetch meaningful content. I could view the content perfectly through my browser, on the same IP address, but through PHP is was a no go.

The first thing I did was stop visiting the site for 15 minutes or so and then increase the time between requests. It briefly worked again but quickly stopped. Next, I opened up php.ini and checked what useragent PHP was using. It turned out to be 'PHP'. I changed that and for the past 3 hours (almost) the script has been working perfectly.

Moral of the story: When scraping content from the web don't make it obvious

It's worth noting that I can't say for sure that it was changing the user agent which fixed the problem, it could have just been coincidence, but it's an easy fix and why make it obvious that you're scraping content?

Options

In this instance I was just working from my development server so I had access to php.ini but I had several options.

I could have added a line to my .htaccess file

php_value user_agent Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1.9) Gecko/20071025 Firefox/2.0.0.9


or used ini_set.

<?php

ini_set('user_agent', 'Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1.9) Gecko/20071025 Firefox/2.0.0.9');

?>


Curl also allows you to specify the useragent.

<?php

curl_setopt($curl, CURLOPT_USERAGENT, 'Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1.9) Gecko/20071025 Firefox/2.0.0.9');

?>


If you want to take cloaking the useragent further with curl this comment in the PHP manual may be useful.


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I think the real moral of the story is stop scraping other people's content without prior consent. If they're blocking you based on your user agent string they're obviously not happy with what you're doing.
#1 Paul Reinheimer (Homepage) on 2007-11-08 02:07 (Reply)
No scraping?!? Paul, you have no sense of adventure, efficiency, or advancement of knowledge. You suggest gathering data by hand? I can think of better things to do with time. I thought computers were for automating tasks, including research. If you don't want your content accessed, don't put it in a system designed to automatically serve it up in response to (HTTP) requests. Don't like the load on your server? Expose a cached API.
#2 Nate on 2007-11-08 04:54 (Reply)
Hi Paul

Thanks for your comment. I realise that scraping content is a sensitive issue but I think in this instance I acted appropriately.

I think it is important to point out that I wasn't reposting the content anywhere else, I was hoping to analyse it in aggregate purely out of personal interest. As such I don't think copyright issues will have come up leaving the issue being (mis)use of server resources.

The file I was scraping was an XML file without formatting which I interpreted as being a fairly safe sign that the file was meant for automated retrieval. It is possible that they had problems with people in the past scraping content with a user agent of 'PHP' but that's so generic that I can't consider it a vote specifically against my efforts.

If I changed my useragent string to 'STREET_CRAWLER' and then a few hours later noticed I was being blocked then it really would be time to reconsider.
#3 Jonathan Street (Homepage) on 2007-11-08 07:56 (Reply)
Random user agent + proxy is the best way ;-)
#4 sf (Homepage) on 2007-11-21 07:02 (Reply)
I guess its a war out there and everything is fair in war. I agree its not a fair practice.
But I am sick and tired of Popups and I have decided that no user from my site will get popup even if he is going to an external site FROM my site. So I use THIS method to get the necessary content effectively. Thanks for this method.

Now I am looking for a method to change the referrer. :-)
#5 NOTRICK (Homepage) on 2007-12-29 21:15 (Reply)
Hello NOTRICK

That's not exactly the usage scenario I had in mind. You're going to use a lot of bandwidth and processor resources with that approach and unless you are thoroughly cleaning the content popups may still be an issue.

I would recommend education about pop-up blockers over this approach though you could use this technique to check whether a site is likely to show your visitors pop-ups.

I suspect that if you read the documentation on cURL changing the referer will be a simple process.
#5.1 Jonathan Street (Homepage) on 2008-01-01 15:40 (Reply)

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