What your Apache Web server is telling the bad guys

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Does your web server give out too much information? Here is how to discover what your Web server is telling the world and how to restrict that information if you have an Apache server.

On most Linux boxes you can use wget to probe a Web server.

wget -S 'www.sitename.com' will show

Server: Apache/1.3.17 (Unix) PHP/4.0.4pl1 mod_perl/1.25

is running on

sitename Web site.

Or you can download ID Serve from Gibson Research at:

Requires Free Membership to View

http://grc.com/id/idserve.htm to run on your Windows 2000 machine. This is a gui program which will show you information similar to wget.

In Apache, you can restrict information given out by setting ServerTokens. See http://httpd.apache.org/docs/mod/core.html#servertokens for the switches to use. For example, adding the line:

ServerTokens Min

to your httpd.conf file will allow only minimal information to be sent out:

Server sends (e.g.): Server: Apache/1.3.0

The default is:

ServerTokens Full (or not specified)

which yields too much information. The server sends, for example

Server: Apache/1.3.0 (Unix) PHP/3.0 MyMod/1.2

If your Apache is newer than 1.3.12, set ServerTokens Prod Server sends (for example)

Server: Apache

Thereby only telling the world you are running Apache. We don't need to advertise that we are running php, mod_perl, etc., as well as the version running. We need to make the bad guys work harder than that.

This was first published in March 2002

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