The two sorts of Referer spam that I see

August 17, 2010

In general, there are two sorts of Referer spam that I see here on WanderingThoughts. The first sort is what I'll call 'plain referer spam', HTTP requests that have Referer URLs that are various spam websites. Many of these are easily recognizable because they are of the form 'http://web.site', with no trailing slash on the end; this is a legal URL, but it is not one that regular browsers ever send. Usually the domain names or the rest of the URL make it pretty clear that this is spam instead of a crazy browser.

(You can enter a website name without the trailing slash, but your browser will almost always add the trailing slash when it actually visits the page. Then when you click on links on the page, it is the slash-added URL that is sent as the Referer.)

The other sort is what I call 'active text', and is much less common. Active text is snippets of actual text in the Referer instead of an URL; I believe I've seen HTML, BBCode, and even an attempt with JavaScript. I find this spam both depressing and intensely irritating, especially the JavaScript. It's depressing because that spammers are doing it implies that there is software that just puts the text from Referer headers on some web page without escaping it first (which is terribly wrong); it's irritating because it's clearly attempting to exploit a security flaw and I'm a sysadmin.

(These Referer headers are clearly bogus; I don't think they even bother pretending by, say, putting a 'http://...' on the front of a garbage word at the start.)

My memory, along with some early entries here, suggests that Referer spam used to be a lot more common than it is now. These days a typical volume is at most one or two attempts a day, and I'm pretty sure that there are days with none at all. Since the spammers are not hitting me with the same Referer over and over, I generally assume that their current goal is to collect links from as many web pages as possible in order to boost their search engine rankings. Naturally they are completely indifferent to the fact that CSpace has no page that shows Referer information, which makes their efforts here completely useless.

(Like email spam, web spam has become something that I no longer pay much attention to unless it is really glaring and in my face.)

PS: if you have public Referer logs, I sugges that you turn them off. If you have private Referer logs that are presented in any sort of web interface, I suggest that you make sure that your software properly quotes and escapes the Referer information. I view my Referer logs in plain text with minimal processing, but I'm aware that this is attractive only to crazy people like me.

(And never, ever investigate a spammed website with anything except an extremely secure browser configuration; you should assume that all of them are absolutely crawling with infectious malware. I use lynx, or sometimes wless.)

Written on 17 August 2010.
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Last modified: Tue Aug 17 01:24:27 2010
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