Obtaining information about the used web server is crucial for any attacker. There may be vulnerabilities in a certain web server version that allow an attacker easy access to the server. Learn how you can prevent them!
Web Server Information Leakage Security Assessment
CVSS Vector: AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
Web Server Information Leakage Vulnerability Information
Obtaining information about the used web server is crucial for any attacker. There may be vulnerabilities in a certain web server version that allow an attacker easy access to the server. To complicate the information gathering process for attackers, the webserver should not provide information about itself, such as its name or version.
This scanner addresses the OWASP Top 10 vulnerability of “Using components with known vulnerabilities.” While making sure you use the latest version of your webserver is crucial, it is an added layer of security if you can prevent attackers from knowing which webserver – and which version you are running.
How to Prevent Web Server Information Leakage
Use one of the following guides to disable information leakage for your webserver:
- Apache
- Apache 2.2
- nginx
Apache
To disable the server signature, which usually contains the name and version of an Apache web server, do the following:
Open the Apache configuration file on your system. This file is usually located at:
/etc/apache2/apache2.conf(Debian, Mint, Ubuntu)/etc/httpd/conf/httpd.conf(Arch, Fedora, CentOS, RHEL).
Depending on the server configuration, there might also be additional configuration files that take care of security configuration, such as /etc/apache2/conf-enabled/security.conf.
Apply the following settings:
https://github.com/crashtest-security/gist/blob/master/fingerprinting/apache_settings
Then reload the webserver configuration:
https://github.com/crashtest-security/gist/blob/master/fingerprinting/apache_configuration
Apache 2.2
In addition to the server signature, Apache version 2.2 has another feature that can leak its version. A header image for the standard installation contains the version information. The problematic image(s) are usually located in/usr/share/apache2/icons/. They are linked to being publicly available as/iconsby an alias configuration. To stop them from being delivered, edit the configuration file/etc/apache2/mods-available/alias.confand remove the following lines:
https://github.com/crashtest-security/gist/blob/master/fingerprinting/apache2.2_settings
Nginx
To disable the version string, which is usually sent by Nginx, update the configuration file, which is usually located at /etc/nginx/nginx.conf , and add to the html section:
https://github.com/crashtest-security/gist/blob/master/fingerprinting/nginx_html_settings
To also disable that the server name is sent, you need the HttpHeadersMoreModule. Run the following command(s) for installation:
https://github.com/crashtest-security/gist/blob/master/fingerprinting/nginx_server_name_disable
For other systems (such as CentOS or RHEL), you must compile the package from the sources described in the installation notes.
Then also add the following line to the config file within the html section and choose a server name of your liking:
https://github.com/crashtest-security/gist/blob/master/fingerprinting/nginx_new_server_name
Limiting Information Provided by IIS
The IIS server also will expose its version in HTTP responses. Microsoft provides UrlScan, which may be used to remove server information from HTTP responses sent by IIS. UrlScan requires IIS6 Metabase compatibility to work. Additionally, the configuration made to IIS is global. If you would like to set up this configuration on a site-by-site basis, check out the UrlScan Setup article by Microsoft.
Enable Metabase Compatibility. find out how to enable Metabase Compatibility using Microsoft’s Installing Metabase Compatibility Support article.
Install UrlScan.
Open the UrlScan.ini file with a text editor. The file is typically located in the %windir%\system32\inetsrv\UrlScan directory.
Search for the key RemoveServerHeader, which by default is set to 0. Set the worth to 1 to remove the Server header.
