Apache Server Vulnerabilities

Apache server

The Apache Web Server

The Apache HTTP Server is a web server application based on NCSA HTTPd. Development of Apache began in early 1995 after work on the NCSA code stalled, and it quickly overtook HTTPd as the dominant web server, and has been the most popular web server in use since April 1996. As of June 2013, Apache was estimated to server 54.2 percent of all active websites, so if you come across a website, there’s a better than even chance that it’s hosted by an Apache server (this site is).

The Apache server supports a variety of features. Many of these features are implemented as compiled modules which extend the core functionality. Some common language interfaces support Perl, Python, Tcl, and PHP. Other features include Secure Sockets Layer and Transport Layer Security support. Because the source code is freely available, anyone can adapt the server for specific needs, and there is a large public library of Apache server add-ons.

Although the main design goal of the Apache server is not to be the fastest web server, Apache does have performance similar to other high-performance web servers. Instead of implementing a single architecture, Apache provides a variety of MultiProcessing Modules (MPMs) which allow Apache to run in a process-based, hybrid (press and thread) or event-hybrid mode, to better match the demands of each particular infrastructure. The multi-threaded architecture implemented in Apache 2.4 should provide for performance equivalent or slightly better than event-based webservers.

Apache Server Vulnerabilities

All software systems have the same general types of vulnerability and Apache is no different. It can be adversely affected by any one of the following problems: [1] poor application configuration; [2] unsecured web-based code; [3] inherent Apache security flaws, and [4] fundamental OS vulnerabilities.

Apache has many default settings that require modification for secure operation. Nearly all configuration information for Apache Web server exists within the httpd.conf file and associated Include files. Because many configuration options exist within these files, it can be easy to make configuration errors that expose the application to attack.

The second manner in which vulnerabilities are exposed is via poorly implemented code on the Apache server. Often, Web developers are far more concerned with business functionality than the security of their code. For instance, poorly written dynamic web pages can be easy denial of service (DoS) targets for attackers, should coded limitations be absent from back-end database queries. Simply publishing confidential or potentially harmful information without authentication can provide enemies with ammunition for attack. For these reasons, you must review and understand not only the Apache application but the information and functionality being delivered via the system.

As with Microsoft’s IIS server, vulnerabilities can exist within the Apache server’s application code itself. There are many means by which hackers can breach or disable an Apache system, such as:

  • Denial of Service (DoS)
  • Buffer overflow attacks
  • Attacks on vulnerable scripts
  • URL manipulation

Occasionally, Apache security flaws are discovered and announced by Apache or by various security groups. The Apache development team is typically quick to respond and distribute patches in response to such events. For this reason, it is critical that you be vigilant in your attention to security newsgroups and to Apache’s security advisory site.

Another source of vulnerability within an Apache web server could occur as a result of foundational security flaws in the OS on which Apache is installed. Apache can be run on just about any OS. You should be very familiar with the specific security vulnerabilities for any OS on which you run Apache.

In the next article, we will discuss the merits of patching and securing the OS as a means of securing your Apache server.

External Links:

The official Apache web site

Apache HTTP Server at Wikipedia

The official Apache Software Foundation web site

Apache web server resource site

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