ServerTokens Prod, ServerSignature Off

July 25, 2005
web

I tend to forget the syntax every time, but one of the first things I do when I setup an Apache web server is add/edit these two directive in my httpd.conf:

ServerSignature Off
ServerTokens Prod

The first one, ServerSignature Off tells apache not to display the server version on error pages, or other pages it generates.

The second one ServerTokens Prod tells apache to only return Apache in the Server header, returned on every page request.

Why do this?

I do this for security reasons. Its not a good idea to broadcast the versions of software your running. While it doesn't make your server any more secure, it may make you less of a target.

What if I am running IIS?

On IIS the Server header does not give as much version detail as Apache, but it can let someone know what primary OS version you are running (eg Windows 2008, 2012, 2012 r2, etc).

One popular way to resolve this is to use the Microsoft URL Rewrite Module to create an outbound rule to rewrite the Server header to a value of your choosing. Hat tip goes to Herman Zindler for posting the outbound rule configuration in the comments:

Precondition: Matching scope: Server Variable Variable name: RESPONSE_Server Variable value: Matches the Pattern Using: Regular Expressions Pattern: .* Action type: Rewrite Value: Whatever you want your server header to be.

Another option for IIS 7-8.5 is the StripHeaders IIS module. This option may potentially be more performant than using Url Rewrite (though I haven't tested that claim). You can find the source code here, and binaries here.

For older versions of IIS you can use Microsoft's Free URLScan tool, the latest version of this tool only supports up to IIS 7 (though it may still work on later versions, it is basically abandonware at this point).

What if my server header says Apache-Coyote/1.1?

This means that the header is coming from Tomcat, you can edit the value of the server header by editing server.xml and adding or editing the server attribute of the <Connector> tags.


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Comments

For Windows servers, is installing UrlScan the only way to address this issue?
Sadly, these no longer work. I added both into the httpd.conf on Debian Squeeze and OpenVAS reported:
Apache Web Server version 2.2.16 was detected on the host.

Have to think of something else :(
Hi Guys,

This is achievable via URLRewrite outbound rule as well for IIS 7.

http://blogs.msdn.com/b/benjaminperkins/archive/2012/11/02/change-or-modify-a-response-header-value-using-url-rewrite.aspx
@vaas, when using URLScan to control this, you would edit the RemoveServerHeader value in the UrlScan.ini file, changing it from the default 0 to 1. Once saved, this change takes effect immediately.

That said, it only affects the Server header, one of two that HackmyCF will detect on a typical IIS-based installation of CF. The other it sees (and will require you to resolve) is the X-Powered-By: ASP.NET header, and Pete shows how to clear that in another technote here, http://www.petefreitag.com/item/722.cfm.
IIS URL rewrite and Helicon ISAPI rewrite do not work well together. We had hundreds of app. pool errors in the windows event logs.


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