CAPTCHA¶

CAPTCHA is available as a method of defense against DDoS attack.

Note

CAPTCHA may also be used as a method of WordPress Brute Force Attack Protection. Please see the WP-Protect Guide for more information about that.

Note

CAPTCHA activation is dependent on the URL being accessed. It does not activate for API URLs. CAPTCHA only activates for URLs accessed by real clients.

Enable globally at the server level¶

Access the WebAdmin console via https://YOUR_SERVER_IP:7080
Navigate to Configuration > Server > Security > CAPTCHA Protection
Set Enable CAPTCHA to Yes. This is the master switch and it is required for both a control panel environment and an LSWS native environment. It will enable the CAPTCHA feature for all control panel Apache virtual hosts as well as LSWS native virtual hosts globally. It may be overridden at the virtual host level.
Choose the CAPTCHA Type you'd like to use for your server. As of v6.4, LiteSpeed Web Server supports the following options:
- reCAPTCHA Checkbox
- reCAPTCHA invisible
- hCaptcha
- ALTCHA
- ALTCHA (invisible)

For other options, hover over the ? symbol to view detailed information about that option.

For demonstration purposes, we will set Trigger Sensitivity to maximum (100), and CAPTCHA Type to reCAPTCHA Checkbox. You may adjust these values according to your needs. Save and restart LSWS. This sensitivity setting will be inherited by all control panel Apache virtual hosts and LSWS native virtual hosts unless overridden at the virtual host level.

After making the change described above, the appropriate directives will be added to the LiteSpeed configuration file found at /usr/local/lsws/conf/httpd_config.xml.

Alternatively, you can add them yourself. Edit the file, and place the following code after the <security>...</security> section:

  <lsrecaptcha>
   <enabled>1</enabled>
   <type>1</type>
   <sensitivity>100</sensitivity>
  </lsrecaptcha>

You can also enable CAPTCHA on an individual virtual host that is under attack, while leaving other websites disabled.

Validation expiration time¶

When a visitor accesses the website, they will need to go through CAPTCHA validation. This validation protects the server against HTTP Flood and other DDoS attacks.

After passing the CAPTCHA validation, the visitor is temporarily whitelisted as long as they continue to browse the site. This makes for a better user experience. Once the visitor has been inactive for a specified time, CAPTCHA is once again enabled for that visitor's next request.

Expiration defaults to one day, but is configurable to any number of seconds via the Verification Expires field.

Override/disable at the virtual host level¶

Assuming you have enabled CAPTCHA at the server level globally, you can override the settings at a virtual host level, but how you do so depends on which environment you are using.

Override/disable for Apache virtual hosts¶

You can configure vhost-level CAPTCHA via the LsRecaptcha directive in the virtual host configuration, like so, and it will override the server setting:

<IfModule LiteSpeed>
   LsRecaptcha 100
</IfModule>

LsRecaptcha has a valid range from 0 to 100.

0 disables CAPTCHA for the virtual host
100 turns on CAPTCHA for every request to the virtual host

You can set it to any value in between 0 and 100 if you want to set Trigger Sensitivity, but we do not recommend this.

Note

The LsRecaptcha directive cannot be used in .htaccess files.

Set max_conn to trigger CAPTCHA¶

In an Apache configuration file, either at the server level, or at the virtual-host level, you can add the LiteSpeed-specific configuration LsRecaptcha max_conn. The parameter value defines the maximum number of concurrent connections you can have before CAPTCHA is automatically triggered.

Example

To set the maximum number of concurrent requests to 1000, use:

<IfModule LiteSpeed>
LsRecaptcha max_conn 1000
</IfModule>

Set the parameter value to 1 if you want to always have CAPTCHA on. Set the value to 0 to disable CAPTCHA.

LsRecaptcha max_conn used at the server level applies to all Apache virtual hosts, but the server-level setting may be overridden with a vhost-level configuration.

Override for LiteSpeed native virtual hosts¶

Use the LSWS WebAdmin console to override CAPTCHA in LSWS native mode.

Navigate to Configuration > Virtual Hosts > Security > CAPTCHA Protection

Set Trigger Sensitivity¶

Trigger Sensitivity refers to the automatic CAPTCHA sensitivity. The higher the value, the more likely CAPTCHA protection will be used. A value of 0 is equivalent to "Off" while a value of 100 is equivalent to "Always On".

Default values¶

Server level: 0. Virtual Host level: inherits server-level setting. Syntax: Integer value between 0 and 100.

LiteSpeed calculates Trigger Sensitivity as the percentage of your server capacity used, based on the number of active connections. CAPTCHA is activated when this formula is true:

Active connections * 100 / Max Connections > (100 - Trigger Sensitivity)

For example:

If Max Connections = 1000, Trigger Sensitivity = 20, and you currently have 900 connections, the formula would be evaluated like so:

900 * 100 / 1000 > 100 - 20

90 > 80

The result is true, so the incoming connection will be given a CAPTCHA test.

Calculating backwards, you can see that when the number of connections drops to less than 800, CAPTCHA will not be invoked.

Warning

We've discovered in real world usage that Trigger Sensitivity can be ineffective in some setups.

Here's why: Trigger Sensitivity is based on the number of active connections. But sometimes, sites have a large number of connections that are unrelated to the main page HTML. These extra connections don't result in anything that is visible to the user, but they require a high connection limit. The high connection limit negatively impacts the Trigger Sensitivity calculation, making most values under 100 behave effectively like 0.

In our experience, the headaches caused by trying to use Trigger Sensitivity under these conditions are not worth the benefits. If you have high connection limits set, we recommend two possible courses of action:

Go all or nothing: set the sensitivity to 100 (always on) or 0 (always off)
Use rewrite rules: Set sensitivity to 0 at the virtual host level, and then selectively enable CAPTCHA for certain URLs via rewrite rules, like the following example, which applies to all URLs in the /admin/ directory.

This is how it would appear if added to the Apache virtual host configuration:

<IfModule LiteSpeed>
RewriteRule /admin/ - [E=verifycaptcha:deny]
</IfModule>

The same rule would need to look a bit different (no beginning / on admin/) if added to .htaccess, like this:

<IfModule LiteSpeed>
RewriteRule admin/ - [E=verifycaptcha:deny]
</IfModule>

Advanced Configuration¶

Define CAPTCHA actions through rewrite rules¶

If you want to further define the CAPTCHA action as deny or drop, or you want to turn CAPTCHA off, you can use one of the following rewrite rule directives:

[E=verifycaptcha]
[E=verifycaptcha:deny]
[E=verifycaptcha:drop]
[E=verifycaptcha:off]

[E=verifycaptcha] will redirect to CAPTCHA until verified (unless it is set to off, which will disable CAPTCHA).

deny will return a 403, and drop will drop the connection when Max Tries is reached. Until Max Tries is reached, the client will be redirected to a CAPTCHA challenge.

Example

RewriteCond SOME-CONDITIONAL-CHECK
RewriteRule .* - [E=verifycaptcha]

(SOME-CONDITIONAL-CHECK would be a suspicious UA, IP address, etc.)

Note

In most cases, rewrite rules will override the default server behavior. However, in cases where Trigger Sensitivity is high, visitors may be sent directly to CAPTCHA before the rewrite rules can even be processed.

Enable CAPTCHA protection for any URL¶

You can enable CAPTCHA for a specific URL. For example, you might want to protect the admin area (/administrator/) for all Joomla sites on the server.

Example

In cPanel, create /etc/apache2/conf.d/userdata/joomlaprotection.conf with the following content:

<IfModule LiteSpeed>
RewriteRule /administrator/ - [E=verifycaptcha:deny]
</IfModule>

Apply to all cPanel virtual hosts and restart LiteSpeed:

/usr/local/cpanel/scripts/rebuildhttpdconf
service lsws restart

Customize the good bots list¶

Google bots are considered good bots because they help index your site. However, they cannot do their job properly without receiving the correct page. The Bot White List configuration may be used to specify bots that you may need for your site.

Here, we have configured Edge in the Bot White List text area. Bot White List is a case-sensitive "contains" match, but regex may be used as well.

After restarting, browsers containing Edge in the user-agent header will bypass CAPTCHA:

The Allowed Robot Hits configuration may be used to limit how many times a good bot (including Googlebot) is allowed to hit a URL before it is redirected to CAPTCHA as well. This may be useful to prevent bad actors from bypassing CAPTCHA using a custom user agent.

Tip

Google and Bing bots are automatically whitelisted. You will need to add any other bots you wish to allow.

Customize the CAPTCHA page¶

The default CAPTCHA page is generic. If you would like to customize the page, you may do so by creating a file at $SERVER_ROOT/lsrecaptcha/_recaptcha_custom.shtml.

There are two script tags that are required and it is strongly recommended to avoid changing the form and the recaptchadiv unless you know what you are doing. There are three echos within the page itself. Those are used by the web server to customize the CAPTCHA type and keys and specify any query string used.

Beyond those required attributes, everything else is customizable. As noted before, please ensure that you have backups of the default page and your customized page. Note that the .shtml extension is required in order to use the LSWS configured type and keys.

Add headers to the CAPTCHA page¶

You can customize the headers on the CAPTCHA page. To do so, add a static context with the URL /.lsrecap/, then add the desired response header for that context, like so:

<IfModule LiteSpeed>
    <Location "/.lsrecap/">
        Header set Access-Control-Allow-Origin "*"
    </Location>
</IfModule>

This snippet cannot be added to .htaccess. It must either be added to an Apache config file, or via the WebAdmin Console for an LSWS Native virtual host.

Example

To add a CORS header to the CAPTCHA page in a WHM/cPanel environment:

Add a <Location "/.lsrecap/"> context to a global include file at /etc/apache2/conf.d/userdata/lsrecaptcha.conf to apply the customization to all virtual hosts
Add a <Location "/.lsrecap/"> context to a virtual host include at /etc/apache2/conf.d/userdata/ssl/2_4/$USER/example.com/lsrecaptcha.conf to apply the customization only to $USER virtual host

Apply your own site key¶

You can apply your own reCAPTCHA key and adjust the configuration as you like from the Google developer reCAPTCHA page.

Tip

When applying for your own key, sign up for reCAPTCHA v2, not v3.

The style of client verification is completely determined on Google's end via their reCAPTCHA service. When given the choice of a checkbox or an invisible badge, you may choose whichever you like. Be aware that the invisible type may sometimes display a difficult puzzle.

For server-wide protection that needs to cover a lot of domains, uncheck Verify the origin of reCAPTCHA solutions. Otherwise, you may need to apply a separate key for each domain. Please refer to the Google doc for more information.

CAPTCHA in ModSecurity Rules¶

You can trigger CAPTCHA through the ModSecurity engine via an environment variable, by adding a rule like this one:

SecRule REQUEST_URI "@contains /test.php" "id:9812419,phase:2,setenv:verifycaptcha=1"

The example above triggers for any URI that contains /test.php.

The value of verifycaptcha should be set to one of the following:

deny: Returns a 403 error.
drop: Drops the connection.
1: Enables CAPTCHA verification without limits. It does not drop the connection or return a 403 error.

Troubleshooting¶

CAPTCHA Returns 403 and Drops Connection¶

If CAPTCHA fails a few times, it will return a 403 error and then drop the connection from that IP. It works this way in order to block attacks. If the reCAPTCHA invisible keeps auto-refreshing and then fails, try changing the CAPTCHA Type.