How can a single line in a blog post take down my server?

I’ve been trying to write a post about a simple Windows Powershell script for the last few hours, but when I try to preview the post with the script included, it takes down my server.

Unfortunately the server isn’t mine to control (it’s hosted by 34sp.com) so I’m limited in what I can do to diagnose the issue – I’m not sure where I’d start anyway.

The problem seems to stem from including the following lines in the post :

<pre>
    $camera_getid.Parameters.Add("@CameraGUID", [System.Data.SqlDbType]"NVarChar").Value = $guid;
</pre>

I’m having trouble narrowing down the problem precisely, since every time it happens, my server is down for about 5-10 minutes.

Has anyone seen anything similar?

Solutions Collecting From Web of "How can a single line in a blog post take down my server?"

WordPress, by default, has no problem with such a content. It won’t crash your server. And I think in fact this does not crash your server as well.

I think your server has some webapplication firewall configured. Such a firewall checks each request for malicious data that are assumed to be triggering exploits or introducing payloads to the server or installed applications.

Those firewalls are often configured with a blacklist that is “best guessed”. This means, they do block requests that are valid as well, because such a firewall can not differ between a valid or invalid request.

Some of those webapplication-firewalls are also interfaced into IP based firewalls. So on seeing a malicious request they block your computer accessing the server for a certain period of time, e.g. 5 to 10 minutes.

Please contact your server administration and ask them if such a firewall exists because you have got problem to post (as in HTTP POST METHOD) the content you named to your host. They should be able to reconfigure the firewall and tweak the rule that is the cause of the false positive.