When disabled, your web server might list the files and subdirectories of any directory on your site if there is no index.html file inside it. This can pose a security risk, so you should always enable this option to avoid this from happening.

Many attackers try to exploit vulnerable extensions on your site by tricking them into including malicious code hosted on the attacker's server. Enabling this option will protect your server against this kind of attacks. This works by preventing any URL which references an http:// or https:// URL in the query string. Sometimes these are legitimate requests. For example, some slideshow plugins use them. In this case you are recommended to use the RFIShield (Remote File Inclusion protection) in the Web Application Firewall and turn this .htaccess Maker option OFF.

PHP has a fun and annoying feature known as "Easter Eggs". By passing a special URL parameter, PHP will display a picture instead of the actual page requested. Whereas this is considered fun, it is also widely exploited by attackers to figure out the version of your PHP installation (these images change between different versions of PHP) and launch hacking attacks targeting your specific PHP version. By enabling this option you completely disable access to those Easter Eggs and make it even more difficult for attackers to figure out the details of your server.

Note: You are advised to also set expose_php to Off in your php.ini file to prevent accidental leaks of your PHP version.

These two files are left behind after any WordPress installation or upgrade and can be directly accessed from the web. They are used by attackers to tell the WordPress version you are using, so that they can tailor an attack targeting your specific WordPress version. Enabling this option will "hide" those files when accessed from the web (a 404 Not Found page is returned), tricking attackers into believing that these files do not exist and making it slightly more difficult for them to deduce information about your site.

Turning on this option will protect you against clickjacking. It does so by preventing your site's pages to be loaded in a, Frame, IFrame or Object tag unless this comes from a page inside your own site. Please note that if your site relies on its pages being accessible through frames / iframes displayed on other sites (NOT on your site displaying content from other sites, that's irrelevant!) then you should not enable this option. If unsure, enable it.

Internet Explorer 9 and later, as well as Google Chrome, will try by default to guess the content type of downloaded documents regardless of what the MIME header sent by the server. Let's say a malicious user to upload an executable file, e.g. a .EXE file or a Chrome Extension, under an innocent file extension as .jpg (image file). When a victim tries downloading this file, IE and Chrome will try to guess the file type, identify it as an executable file and under certain circumstances executing it. This means that your site could be unwittingly used to serve malware. Such an event could result in your site being blacklisted by browser makers and cause their browsers to display a warning to users when visiting your site. By enabling this feature you instruct IE and Chrome to respect the file type sent by your server, eliminating this issue. See the relevant MSDN article for more information.

When enabled the browser will be instructed to prevent reflected XSS attacks. Reflected XSS attacks occur when the victim is manipulated into visiting a specially crafted URL which contains Javascript code in it. This URL leads to a vulnerable page which outputs this Javascript code verbatim in the page output ("reflects" the malicious code sent in the URL).

This is a commonly used method used by attackers to compromise web sites, especially when a zero-day XSS vulnerability is discovered in popular WordPress plugins or WordPress itself. The attacker will try to trick the administrators of websites into visiting a maliciously crafted link. If the victims are logged in to their site at that time the malicious JavaScript will execute, typically giving the attacker privileged information or opening a back door to compromising the site.

Enabling this option in .htaccess Maker will instruct the browser to try preventing this issue. Please note that this only works on compatible browsers (IE8; Chrome; Safari and other WebKit browsers) and only applies to reflected XSS attacks. Stored XSS attacks, where the malicious JavaScript is stored in the database, is NOT prevented. You should consider this protection a safety belt. Not wearing a safety belt in the event of an accident pretty much guarantees serious injury or death. Wearing a safety belt minimises the possibility of injury or death but does not always prevent it. This option is your safety belt against the most common type of XSS attacks. You should use it but don't expect it to stop everything thrown your way. Always keep your software up-to-date, especially when a security release is published!

For more information please consult the relevant MSDN article.

By default Apache and PHP will output HTTP headers advertising their existence and their version numbers. If you are always using the latest and greatest versions this may not be a problem, but the chances are that your host is using an older version of both software. Giving away the version numbers of the server software in every request makes it trivial for an attacker to obtain information about your site which will help them to launch a tailored attack, targeting known security issues in the versions of Apache and PHP you're using. Enabling this option will mitigate this issue. Please note that this is SECURITY THROUGH OBSCURITY which is NEVER, EVER an adequate means of protection. It's just a speed bump in the way of an attacker, not a roadblock.

You are strongly advised to keep your server software up-to-date. If you're not managing your own server, e.g. you're using a shared host, we very strongly recommend choosing a hosting service which follows this rule. As a simple test, if your server is not currently using one of the PHP versions published in the top right corner of http://php.net (or at most one version earlier, i.e. the third number of the version on your server is one less than the one listed on php.net) the chances are that your server is using outdated, vulnerable server software. Remember that outdated versions of PHP and Apache, even with some security patches backported, CAN NOT be secure. There's a good reason new software versions are published regularly. For example a popular but woefully outdate version of PHP is PHP 5.3.3. It has a MAJOR issue regarding bcrypt encryption, fixed in 5.3.10 and NOT backported by any vendor to an earlier version of PHP. As a result using PHP 5.3.3 makes your site's passwords insecure.

Enabling this feature instructs proxy servers and caches to not convert your content. For example, certain proxy servers (typically found in mobile networks, businesses and ISPs in congested areas) will attempt to scale and aggressively compress images, CSS and Javascript to save bandwidth. This can lead to several issues, from displayed images being a bit off to your site breaking down because the compressed CSS/JS introduced errors preventing the browser from parsing it correctly. With this feature enabled the cache and proxy servers will be instructed to not do that by setting an HTTP header. If they respect the HTTP header (they should, it's a web standard) such issues are prevented.

For more information please consult the formal web standard document RFC 2616, section 14.9.5

When enabled, it will block any site access attempt if the remote program sends one of the user agent strings in the User agents to block, one per line option. This feature is designed to protect your site against common bandwidth-hogging download bots and otherwise legitimate tools which are more usually used for hacking sites than their benign intended functionality.

The user agent strings to block from accessing your site. You don't have to enter the whole UA string, just a part of it. The default setting includes several usual suspects. Separate multiple entries by a single newline character (that is a single press of the ENTER key). Do note that some server with mod_security or mod_evasive installed will throw an "Access forbidden" message if you try to save the configuration settings when this field contains the word "WGet". If you come across this issue it is not a bug with Admin Tools or WordPress, it is a server-level protection feature kicking in. Just avoid including the word Wget and you should be out of harm's way.