SQL injection attacks are one of the most common forms of hack attacks that threaten the security of WordPress websites. SQL injections target WordPress sites that use an SQL database – MySQL, Oracle, SQL Server, etc. In this form of attack, the hacker injects a malicious SQL code into the WordPress database in an attempt to retrieve critical and sensitive data.
Let us understand SQLi (i stands for injecting, as in injecting code) attacks, how they occur and what harm do they cause. Before doing so, a quick refresher on how WordPress database works. This is crucial to understanding SQL injection attacks manipulate the database to retrieve, edit or delete the database content.
1. WordPress database & SQL queries
As you would know, WordPress is made of files and database. The files comprise of the WordPress plugins and themes, core WordPress files, etc. The database contains all the content or data of the site – blog posts, pages, media library, comments, etc. The database, just like your website, needs a management system for the user to manage it.
MySQL is the default database management system for most WordPress installations. Whenever a user needs to interact with the database, he/she uses SQL queries to do so. Be it to edit, manage, retrieve, view or delete the data inside the database.
Even site interactions such as viewing blog posts or pages are carried out using SQL queries. For instance, whenever a user clicks on a page to view it, this request comes an SQL query. It then consults the database for the requested page. The page is then rendered to the visitor in a user-friendly format, again, with using SQL queries. So SQL queries are the commands that determine how a WordPress site behaves.
2. How is the database manipulated by a hacker?
This interaction with the database that we described in the above section need not only happen from the control panel or through a WordPress admin account. Most sites allow visitors to input content or information – comments on posts, contact information or queries through the contact us page, etc. As we mentioned earlier, the database stores all the data on the site. That includes comments to posts, visitor’s contact information, and queries, as well.
The form elements that hackers typically try to manipulate include contact forms, login portals, blog comment forms, subscription pop-ups, eCommerce checkout pages, search bars, etc. When these elements have exposed vulnerabilities in them, hackers find it easy to inject SQL queries into the database through them.
For instance, consider a scenario where you have a form plugin installed into your site. And a form which requires the user to input his/her phone number. In a site where these fields are not configured to accept only numerical data entry, the hacker could easily input a malicious SQL command. A single contact form can easily become an entry point for hackers.
3. Types of SQLi attacks
There are different types of SQLi attacks that hackers launch on vulnerable WordPress sites. Depending on the results hackers want, the SQLi attacks could be of different types such as in-band SQLi, inferential SQLi, and out-of-band SQLi. Each of these attacks is carried for different purposes. Let us explore what they are in a little detail.
i. In-band SQLi
This is the most common type of WordPress SQL injection attack that hackers often launch on websites. Primarily because they are really easy to carry out and the results are often good. This type of attacks are typically done to gather some critical information from the database. This type of SQLi attacks are further divided into two: Error-based SQLi and Union-based SQLi.
Error-based SQLi attacks are those where hackers launch command to your site’s database. And when the database returns an error message, it gives them an insight into the structure of the database. The database error messages are very valuable to developers during the development stage. They are able to correctly assess from the message what is wrong so that it can be rectified immediately.
Union-based SQLi is a type of SQL injection attacks that uses the Union statement or a combination of two select statements to obtain data from the database.
ii. Inferential SQLi
Sometimes referred to as Blind SQLi, Inferential SQLi are a little more time consuming, unlike in-band SQLi attacks. Since this attack takes longer to execute and the results are also not immediate, it is called a blind SQL injection or Blind SQLi. Since there is no output (not even an error message) the hackers use other ways to retrieve data. This kind of attack is often carried out using automated tools since it may otherwise take days to retrieve information.
Blind SQLi is again divided into two types: Boolean-based SQLi and time-based SQLi. In Boolean-based SQLi attacks, the data is extracted by asking true or false questions to the database. Time-based SQLi injects a SQL segment that induces a time delay. Depending on how much time it takes for the server to respond, hackers get some useful insight into SQL injection vulnerabilities in the site that they can then exploit.
iii. Out-of-band SQLi
This is not a very common attack since it requires certain features to be enabled in the website database for it to be executed. These features are essential because they enable the hacker to communicate with the website. It is this precondition that makes this hack harder to execute. Also, Out-of-band SQLi attacks are launched as an alternative to in-band SQL or interferential injection. That is because inferential time-based techniques require stable server responses. And if these responses aren’t stable, then this technique is ineffective.
Depending on the type of server and the purpose of the attack, hackers use any of these above-mentioned attacks to get unauthorized access to the site. And once launched, these attacks can have very severe consequences on your site. Let us explore what the consequences of an SQLi attack are for your site.
4. What are the consequences of an SQLi attack?
The SQLi attack targets the database, which is where all the critical data is stored. An SQLi attack allows unauthorized access to the database and this can have disastrous consequences as listed below.
- The database contains critical information about the WordPress users, such as their credentials. This can then be used to impersonate these users and make use of their privileges on the site.
- Not just the user credentials, but the entire data in the database is at the mercy of the hacker if he gains unauthorized access to the database.
- Apart from merely accessing data in the database, this attacks also allows the hacker to modify data. This can have very serious implications for the site and your business.
- The hacker could also delete critical data from your site that may even affect the functionality of your site.
Note: With your data at risk with such attacks, it is crucial that you backup data regularly. You can do this either manually or using a plugin such as BlogVault. The plugin offers daily and on-demand automated backups to keep your data safe.
5. How does WordPress handle such attacks?
In order to prevent these types of SQLi attacks, WordPress has a system in place. One that validates, sanitizes and escape data. Let us elaborate on these.
By validating that the data entered by the visitor matches with the one specified in the criteria, WordPress can restrict the characters that can be entered into the forms. For instance, when a data field requires the visitor to input a phone number, WordPress can check if the information entered is in the format specified for a phone number. If for instance, a visitor inputs data in the field that doesn’t conform to the specified criteria, WordPress sanitizes or cleans those characters that are not allowed. And this is done before adding it to the database.
Escaping is another step in the process where WordPress secures whatever data is presented to users on the site.
However, despite all these processes in place, WordPress is not fully secure against SQLi attacks. That is because even though WordPress has taken precautions to secure its core files (in a 2017 security update that was published) against SQL attacks, plugins and themes are a different story. The vulnerabilities of plugins and themes used are at the mercy to be exploited by a hacker.
6. How to prevent SQLi attacks on your WordPress site?
One can scan for SQL injection using a website security service. But first, take a step back and look at certain website security measures that need to be in place to protect your site from SQLi attacks. Here we explore 6 important ones.
i. Use trusted WordPress plugins/themes
This point holds true to prevent all types of hacks. That’s because hackers typically exploit the vulnerabilities of plugins and themes to hack WordPress sites. So make sure that you install plugins and themes from trusted sources.
Another good practice is to check when was the plugin or theme last updated. This will reveal important information about the health and hygiene of the plugin. It’ll also reveal whether the developer has regularly worked towards fixing any security vulnerabilities that come up in it. Not only would you be spending a great deal of money and effort fixing the hack, but many a time these hacks take a lot of time too. This can be detrimental to your business and brand!
ii. Update everything
The most common way that hackers launch SQLi attacks on WordPress sites is by exploiting security threats in plugins and themes. These security lapses are patched through security updates that are issued from time to time. Therefore it is very important that these security updates reflect in your installations as well. And that can be done by updating your plugins and themes regularly.
Updating the themes and plugins is a task that needs to be given the foremost priority. In order to be regular with the updates, it is a good idea to install an automated plugin that alerts you in case of any pending updates.
iii. Restrict field entry type
SQLi attacks work by exploiting vulnerabilities in the form elements of the website. In order to prevent such attacks, it is important to configure each input field to allow only characters that pertain to that particular entry. That is, for a name field, allow only alpha entries; for a phone number entry, allow only numeric values and not special characters. This will go a long way in preventing most SQLi attacks.
iv. Sanitize form fields
Apart from these measures, you can also use the function sanitize_tect_field() so as to reject entries that do not follow the aforementioned criteria.
v. Change the default database prefix
WordPress database uses wp- as the default prefix. A simple trick to make it harder for the hacker to access database is to change this default prefix and customize it to something of your choosing. This would make it hard for the hacker to execute SQL queries since they wouldn’t know where to launch the attack.
Pic: An example of a folder with a wp prefix
vi. Keep a log of all database activities
It is also a good idea to keep a log of all the database activities. That allows you to keep track of all the changes occurring on the database. Any time an unauthorized change is made, you will be alerted immediately.
vii. Use a website application firewall
A website application firewall or WAF can protect your website by detecting SQLi attack attempts by analyzing form inputs. Apart from detecting these attacks, WAFs also effectively block bad IPs from attacking your site.
7. Secure your WordPress website at all times
Implementing these security measures will ensure that your site is well protected from malicious SQLi attacks. A WordPress security plugin such as MalCare goes a long way in securing a WordPress site against such malicious attacks. Apart from its advanced security features such as firewall protection, login protection against brute force attacks, WordPress management, manage users, manage plugins and themes, MalCare also has the most advanced malware scanner that can detect even hidden malware. So the moment it detects any malware attack attempt on your site, it alerts you of the presence of malware. And you can instantly clean it with just one click. For more information on web security feel free to check our in-depth WordPress security guide.
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