20 ways to Secure your Apache Configuration
Here are 20 things you can do to make your apache configuration more secure. Disclaimer: The thing about security is that there are no guarantees or absolutes. These suggestions should make your server a bit tighter, but don’t think your server is necessarily secure after following these suggestions. Additionally some of these suggestions may decrease performance, or cause problems due to your environment. It is up to you to determine if any of the changes I suggest are not compatible with your requirements. In other words proceed at your own risk
First, make sure you’ve installed latest security patches
There is no sense in putting locks on the windows, if your door is wide open. As such, if you’re not
patched up there isn’t really much point in continuing any longer on this list. Go ahead and
bookmark this page so you can come back later, and patch your server.
Hide the Apache Version number, and other sensitive information.
By default many Apache installations tell the world what version of Apache you’re running, what
operating system/version you’re running, and even what Apache Modules are installed on the
server. Attackers can use this information to their advantage when performing an attack. It also
sends the message that you have left most defaults alone.
There are two directives that you need to add, or edit in your httpd.conf file:
The ServerSignature appears on the bottom of pages generated by apache such as 404 pages,
directory listings, etc.
The ServerTokens directive is used to determine what Apache will put in the Server HTTP
response header. By setting it to Prod it sets the HTTP response header as follows:
If you’re super paranoid you could change this to something other than “Apache” by editing the
source code, or by using mod_security (see below).
Make sure apache is running under its own user account and group
Several apache installations have it run as the user nobody. So suppose both Apache, and your mail
server were running as nobody an attack through Apache may allow the mail server to also be
compromised, and vise versa.
Ensure that files outside the web root are not served
We don’t want apache to be able to access any files out side of its web root. So assuming all your
web sites are placed under one directory (we will call this /web), you would set it up as follows:
Deny from all
Allow from all
Note that because we set Options None and AllowOverride None this will turn off all options and
overrides for the server.
Turn off directory browsing
You can do this with an Options directive inside a Directory tag. Set Options to either None or –
Turn off server side includes
This is also done with the Options directive inside a Directory tag. Set Options to either None or
Turn off CGI execution
If you’re not using CGI turn it off with the Options directive inside a Directory tag. Set Options
to either None or -ExecCGI
Don’t allow apache to follow symbolic links
This can again can be done using the Options directive inside a Directory tag. Set Options to
either None or -FollowSymLinks
Turning off multiple Options
If you want to turn off all Options simply use:
If you only want to turn off some separate each option with a space in your Options directive:
Options -ExecCGI -FollowSymLinks -Indexes
Turn off support for .htaccess files
This is done in a Directory tag but with the AllowOverride directive. Set it to None.
If you require Overrides ensure that they cannot be downloaded, and/or change the name to
something other than .htaccess. For example we could change it to .httpdoverride, and block
all files that start with .ht from being downloaded as follows:
<Files ~ “^\.ht”>
Deny from all
mod_security is a super handy Apache module written by Ivan Ristic, the author of Apache Security
from O’Reilly press.
You can do the following with mod_security:
• Simple filtering
• Regular Expression based filtering
• URL Encoding Validation
• Unicode Encoding Validation
• Null byte attack prevention
• Upload memory limits
• Server identity masking
• Built in Chroot support
• And more
Disable any unnecessary modules
Apache typically comes with several modules installed. Go through the apache module
documentation and learn what each module you have enabled actually does. Many times you will
find that you don’t need to have the said module enabled.
Look for lines in your httpd.conf that contain LoadModule. To disable the module you can
typically just add a # at the beginning of the line. To search for modules run:
grep LoadModule httpd.conf
Here are some modules that are typically enabled but often not needed: mod_imap, mod_include,
mod_info, mod_userdir, mod_status, mod_cgi, mod_autoindex.
Make sure only root has read access to apache’s config and binaries
This can be done assuming your apache installation is located at /usr/local/apache as follows:
chown -R root:root /usr/local/apache
chmod -R o-rwx /usr/local/apache
Lower the Timeout value
By default the Timeout directive is set to 300 seconds. You can decrease help mitigate the potential
effects of a denial of service attack.
Limiting large requests
Apache has several directives that allow you to limit the size of a request, this can also be useful for
mitigating the effects of a denial of service attack.
A good place to start is the LimitRequestBody directive. This directive is set to unlimited by
default. If you are allowing file uploads of no larger than 1MB, you could set this setting to
If you’re not allowing file uploads you can set it even smaller.
Some other directives to look at are LimitRequestFields, LimitRequestFieldSize and
LimitRequestLine. These directives are set to a reasonable defaults for most servers, but you may
want to tweak them to best fit your needs. See the documentation for more info.
Limiting the size of an XML Body
If you’re running mod_dav (typically used with subversion) then you may want to limit the max size
of an XML request body. The LimitXMLRequestBody directive is only available on Apache 2, and
its default value is 1 million bytes (approx 1mb). Many tutorials will have you set this value to 0
which means files of any size may be uploaded, which may be necessary if you’re using WebDAV
to upload large files, but if you’re simply using it for source control, you can probably get away
with setting an upper bound, such as 10mb:
Apache has several configuration settings that can be used to adjust handling of concurrent requests.
The MaxClients is the maximum number of child processes that will be created to serve requests.
This may be set too high if your server doesn’t have enough memory to handle a large number of
Other directives such as MaxSpareServers, MaxRequestsPerChild, and on Apache2
ThreadsPerChild, ServerLimit, and MaxSpareThreads are important to adjust to match your
operating system, and hardware.
Restricting Access by IP
If you have a resource that should only by accessed by a certain network, or IP address you can
enforce this in your apache configuration. For instance if you want to restrict access to your intranet
to allow only the 176.16 network:
Deny from all
Allow from 126.96.36.199/16
Or by IP:
Deny from all
Allow from 127.0.0.1
Adjusting KeepAlive settings
According to the Apache documentation using HTTP Keep Alive’s can improve client performance
by as much as 50%, so be careful before changing these settings, you will be trading performance
for a slight denial of service mitigation.
KeepAlive’s are turned on by default and you should leave them on, but you may consider changing
the MaxKeepAliveRequests which defaults to 100, and the KeepAliveTimeout which defaults to
15. Analyze your log files to determine the appropriate values.
Run Apache in a Chroot environment
chroot allows you to run a program in its own isolated jail. This prevents a break in on one service
from being able to effect anything else on the server.
It can be fairly tricky to set this up using chroot due to library dependencies. I mentioned above
that the mod_security module has built in chroot support. It makes the process as simple as adding
a mod_security directive to your configuration:
There are however some caveats however, so check out the docs for more info.