The notorious Error 404 Not Found stands firmly at the top of the list of most common website issues. Encountering this HTTP status code indicates that your requested page is nowhere to be found on the server.
A 404 Page Not Found error most typically occurs when a page or resource can’t be tracked down — often the result of it being moved or deleted entirely from the server. However, 404’s can also happen due to a mistyped URL leading to a dead or broken link, or a page that has been relocated without a proper 301 redirect.
Too many unexpected 404 errors can sour the user experience for your visitors and increase bounce rates, potentially impacting your website’s rankings and traffic.
Despite the prevalence of this client-side issue, troubleshooting a 404 is often a quick and painless task. In this article, we’ll delve into the primary causes of 404’s and outline a number of ways to fix these pesky errors on your website.
Contents:
- What is error 404?
- How are 404 errors different from other client side errors?
- What are the most common causes of a 404 error?
- How do I fix a 404 error on my website?
- Can a 404 error be caused by malware?
What is error 404?
A 404 error is a client-side error that manifests when the server of a particular website fails to locate the requested page. This implies that the client (your browser) manages to connect with the host (the server of the website) successfully. However, the host is unable to locate the precise resource that was requested, such as a specific URL or filename.
The Internet Engineering Task Force defines error 404 as follows:
The 404 (Not Found) status code indicates that the origin server did not find a current representation for the target resource or is not willing to disclose that one exists.
A 404 status code does not indicate whether this lack of representation is temporary or permanent; the 410 (Gone) status code is preferred over 404 if the origin server knows, presumably through some configurable means, that the condition is likely to be permanent.
Examples of a 404 error:
As an illustration, if someone attempts to access https://example.com/example-post-name but there’s no content on the site with the slug example-post-name, a 404 error would be displayed in your browser. This is because although the web server is operating normally, it couldn’t locate the requested resource.
This error is not limited to posts or pages either. Any missing assets can trigger a 404 error on the server, including missing image files, JavaScript, CSS, and so forth.

404 error messages can appear in various formats, but they all mean the same thing. Here are a few variations of 404’s you might encounter in your browser:
- 404
- 404 Not Found
- 404 Error
- Error 404: Not Found
- HTTP Error 404
- Temporary Error (404)
- We can’t find the page you’re looking for.
- The requested URL was not found on this server.
- The website cannot display the page – HTTP 404.
- Is currently unable to find this request. HTTP ERROR 404.
These are just a handful of the potential messages you might see when encountering a 404 error. In fact, many modern websites set up their own custom “404 not found” error pages to entertain and assist visitors.
Sometimes, 404 error pages are even visually indistinguishable from a normal home page, but their HTTP headers explicitly report the status: “HTTP/1.1 404 Not Found”
How is error 404 different from other client side errors?
There are many types of client side error codes and they all mean different things.
To help you understand the difference between 404 errors and other types of 4xx errors, we’ve outlined some of the common types of client side responses you might encounter in your browser.
| Client Error | Description |
| 400: Bad Request | This error code means that the server couldn’t understand the request due to invalid syntax or request message framing, or deceptive request routing.. |
| 401: Unauthorized | This error indicates that the client lacks valid credentials and must authenticate itself to get the requested response. |
| 402: Payment Required | This status code is a non-standard response indicating that the client must make a payment to access the requested resource. |
| 403: Forbidden | This status code indicates that the server has received and understood the request but is unable to authorize it. |
| 404: Not found | This status code is one of the most common errors and simply means that the server can’t find the requested resource. |
| 405: Method Not Allowed | The server has recognized the method, but it has been disabled or cannot be used. |
| 406: Not Acceptable | The server cannot produce a response matching the list of acceptable values defined in the request’s headers. |
| 407: Proxy Authentication Required | This is similar to a 401 error, but it indicates that the client must authenticate itself with a proxy. |
| 408: Request Timeout | This error occurs when the server would like to shut down a non-responsive connection. |
| 409: Conflict | This means that the request could not be completed due to a conflict with the current state of the server. |
| 410: Gone | This status code is used to indicate that the requested resource is no longer available and will not be available again. |
Now that we’ve got a handle on the various types of client side errors, let’s take a look at some of the potential causes for a 404 error on your website.
What are the most common causes of a 404 error?
A 404 error is a specific issue indicating that a requested resource on a website cannot be found. These can arise from various minor to severe issues.
Unlike 401 or 403 errors, a 404 error doesn’t typically provide a precise explanation of the problem (nor a direct solution).
Let’s examine some potential causes of a 404 on your site:
- The requested URL is incorrect or has been changed
- The requested web page or resource has been deleted from the server
- The resource exists, but your website’s configuration or file permissions have been altered and web server processes can’t locate it
- Broken or dead links within your website point to a web page that doesn’t exist
- The website’s sitemap is outdated and web crawlers are still trying to access non-existent URLs
- There was a change in your website’s domain name
- There are incorrect redirects or rewrites in the .htaccess file
- The requested web page or resource never existed in the first place
How do I fix a 404 error on my website?
Here are a few ways to troubleshoot 404 errors to get your broken pages back up and running — and get rid of links pointing to non-existent pages.
- Clear your browser cache
- Refresh the web page
- Check your permalinks
- Check your .htaccess file
- Scan for broken links
- Set up 301 redirects
- Check for recent software updates
1. Clear your browser cache
This is a good troubleshooting step. This confirms that the problem isn’t caused by cached data on your end.
Here’s how to clear your cache on Google Chrome.
- Launch your Chrome browser.
- Locate and click on the icon with the three dots icon at the top right of the window.
- Navigate to More tools then click on Clear browsing data.
- Click on the Time Range field, then select one of the options that appear. To delete everything, select All time.
- Select Clear data to clear the cache.
You have the choice to clear just your browsing history, or for a more comprehensive cache purge, include cookies and other site data as well.
Important note: This action will erase some website settings and log you out of current sessions, requiring you to sign in again. Certain websites may also appear to load slower as content and images will need to be reloaded.
2. Refresh the web page
Wait a moment, then try refreshing the page by hitting F5 or Ctrl + F5 on your keyboard. Your website’s server might be busy, so this step is worth a shot. You might also want to try accessing the site using a different web browser to see if the 404 error persists.
To make sure you’re not viewing an older version of the page stored in your browser’s cache, try adding “?checkcache” at the end of youe website’s URL like this: example.com?checkcache
3. Check your site’s WordPress permalinks
If you’re seeing 404 errors everywhere on your website when you try to open a page, it could be an issue with your WordPress permalinks.
The best way to check this is to refresh your permalink settings on your WordPress site. Just go to Settings > Permalinks, and click on Save Changes.

You don’t have to modify any of the settings, just try clicking Save Changes at the bottom of the page to check if this resolves your site-wide 404 error issue.
4. Check your .htaccess file
If you have an Apache server and are still experiencing 404 errors after trying the first three steps, you can check to identify if your .htaccess file is the culprit.
Sometimes, this file may encounter issues as a result of incompatible or malicious plugins, or incorrect settings. If your .htaccess has been damaged, tampered with, or incorrectly modified, it might mess up your website and cause a 404 error page to show up.
To troubleshoot this, you can try disabling your old .htaccess file and creating a brand new one with the following generic rules:
# BEGIN WordPress <IfModule mod_rewrite.c> RewriteEngine On RewriteBase / RewriteRule ^index\.php$ - [L] RewriteCond %{REQUEST_FILENAME} !-f RewriteCond %{REQUEST_FILENAME} !-d RewriteRule . /index.php [L] </IfModule> # END WordPress
You can locate your .htaccess file by accessing your website files through a file manager like cPanel or via FTP/SFTP. The file will most likely be located in your public_html directory. However, there’s a good chance your server will hide this file from view by default and you’ll need to toggle hidden files to see it.
If you’re still encountering a 404 after checking for issues with your .htaccess file, you can take a look at missing redirects.
5. Scan for broken links
Next, you’ll want to identify if your website is unexpectedly redirecting users to missing or non-existent pages and resources via broken links. You can accomplish this by reviewing your Google Console’s Page Indexing report to check which pages are 404’ing.
Google suggests the following:
In general, we recommend fixing only 404 errors that you link to yourself or list in a sitemap. If a page has been moved, you should return a 3XX redirect to the new page.
Here’s some general guidelines from Google for how you should handle 404 errors:
- Fix the error if it’s a submitted URL.
- Allow 404s for deleted pages without replacements or bad URLs that never existed on your site.
- Redirect commonly misspelled or alternately spelled URLs to the correct page.
- If the URL was submitted for indexing and shows an error, inspect the source and update the sitemap if required.
- Add a redirect if the content has moved.
- Allow 404 or 410 for permanently deleted content not meant to be replaced.
- Redirect very common errors to appropriate pages.
- 404 errors may occur due to non-existent URLs found in JavaScript, Flash files, or other embedded content, or that only exist in a sitemap.
- Note that URL removal requests won’t remove the error from your report.
So, gather up a list of broken links that you find on either your site or your sitemap and either fix them, or set up some redirects in the next step.
6. Set up 301 redirects for any moved or modified content
If you’re encountering 404’s for a specific page, it’s quite possible that you’ve either:
- Altered the URL for the post or page, or;
- Manually moved the post or page, for example by deleting the existing page and pasting it to an entirely new one.
If this is the case, users who try to access the page or post at the old URL will encounter a 404 error page instead of the content they were looking for. The best course of action is to set up a 301 redirect to automatically send users to the new destination. (Bonus: This will also be favorable for your hard-earned SEO, as well.)
If you use WordPress, it may try to automatically redirect any moved or changed content on your site — but it doesn’t always catch everything perfectly. However, you can leverage Yoast SEO or other popular WordPress plugins to set up redirects for any of your migrated content.
How to create 301 redirects on WordPress with Yoast SEO:
- Download and install the Yoast SEO plugin.
- Navigate to the Redirects tab.
- Select 301 Moved Permanently from the redirect Type.
- Enter the old URL that you want to redirect from, then define the new URL destination that you want to send traffic to.
- Click the Add Redirect button.

If the issue isn’t related to a missing redirect for your post or page, then you’ll need to move on to the next step for further troubleshooting.
7. Check for recently installed or updated software
In some cases, 404’s can occur if a broken plugin was installed on your website.
So, you’ll want to audit your website for any new and unfamiliar plugins or themes. If you find anything unusual, this could be an indicator of compromise.
Investigate further to pinpoint:
- What the unfamiliar software or component is
- How long it’s been installed on your website
- Whether or not it’s from a legitimate source
If you encounter any suspicious looking software, remove the unfamiliar plugin or theme and scan your website for malware.
Note: Attackers regularly scan for vulnerable or outdated and poorly maintained themes, plugins, and other software. They run automated scripts to target any sites they find with vulnerabilities. So as a rule of thumb, always keep your software updates with the latest security patches or virtually patch your website with a firewall to mitigate risk.
Can error 404 be caused by malware?
Hackers typically exploit compromised websites — this can range from injecting additional code into existing files to generating thousands of malevolent files and posts.
In some cases, website malware can result in unexpected 404’s on a website. However, this is not extremely common and you shouldn’t assume right off the bat that your website has been pwned just because you’ve got a 404 error.
Let’s take a look at a couple of scenarios that can severely disrupt your website’s operation and result in 404’s:
- Hackers delete entire files or directories from the server
- Injected malicious code contains syntax errors or is improperly injected, breaking valid code
- Spam doorway pages created by hackers may be based on a template from a third-party site whose entire link structure is different
- Hackers completely replace legitimate code with their own, breaking any site functionality that depended on the original legitimate file
- Hackers encrypt legitimate files and change their names
- The database becomes partially corrupted during compromise
- An attacker runs their own tools on the server, exhausting available resources required for site functionality (ie. cryptominers, DDoS bots, spam servers)
- Attacker modifies the .htaccess file to retrieve 404 pages from a malicious site
Every day hackers probe millions of websites for known security vulnerabilities. They may try to access certain files to figure out if a website contains a vulnerable component. Quite often they don’t find what they are looking for, but this activity may leave many 404 errors in your server logs.
Hackers may also try to access already deleted backdoors, which will also be visible as 404’s in server logs. However, such 404’s should not make you think that the backdoor is really missing. Sometimes fully-functional backdoors generate 404 errors on purpose, just to make webmasters think that it’s not there.
And yet another example is when hackers add backdoor code to a WordPress theme’s 404.php file. To access the backdoor, they don’t have to reveal its location — they just need to access any non-existent URL on the compromised website.
Example of how .htaccess malware can cause 404 errors
The .htaccess file, a powerful tool specific to Apache server environments, enables you to modify and configure your website’s environment without making changes to server config files.

Conversely, the .htaccess file is also a favorite target for attackers, who exploit it to conceal malware, redirect users, alter php.ini values, and perform other malicious activities. Due to its hidden nature (it starts with a “.”), many site owners overlook this file, making .htaccess malware tricky to identify and clean.
Common attacks include .htaccess redirects, which mislead users from search engines to malware-infected sites, and error page redirections to malware, which can be even more challenging to detect as the rest of the website appears to function normally.
For example, here’s an .htaccess file entry that retrieves 404 error pages from a malicious site:
ErrorDocument 404 http://genericdrugeshop[.]eu/Other misuses of the .htaccess file include spam link generation, which can produce hundreds of spam links on the website, impacting the site’s SEO and resulting in blocklisting by Google.
In some instances, attackers exploit .htaccess files to deny access to website files, disrupting site functionality and impeding website administrators from performing maintenance, updates, or taking down the site. All of these malicious activities can in theory result in 404 errors on your website.
Resolving client side errors due to malware
Client side errors can be a source of frustration, but after following these troubleshooting steps you should be able to get your posts and pages working in no time.
Keep in mind that 404’s are most commonly caused by forgotten redirects, broken links, caching issues, and accidentally deleted content.
If you’ve followed these troubleshooting steps and suspect that your .htaccess file has been tampered with or infected by some malware, you can refer to our free guide on how to remove malware from a website.
Our experienced security analysts are always happy to help clean up an infected website, too! Satisfaction guaranteed.





![Malware comes in many different varieties. Analyst Krasimir Konov is on this month’s Sucuri Sit-Down to help keep them all straight. From malicious iframes to SEO spam, join host Justin Channell as he racks Krasimir’s brain on all the different types of malware. Also, Krasimir discusses his recent blog post about a malicious cURL downloader, and Justin breaks down the latest website security news, including patched plugins you should update. Podcast Transcript Justin Channell: Hello, and welcome to the Sucuri Sit Down. I'm your host, Justin Channell, and this is a monthly podcast about website security, where we get in-depth with the malware removal experts here at Sucuri. Later in the show, I'll have our analyst Krasimir Konov to chat about some different types of malware, but first, let's take a look at other topics we've published on our blog and Sucuri labs notes this month. First up, we have some new information about credit card skimming with hackers using a hybrid method to steal payment information from eCommerce websites. Our analyst Dennis Sinegubko wrote about this for the Sucuri blog back at the beginning of June. Now, most credit card stealing malware is a client side JavaScript that grabs data and sends it to a third party server. But, that approach has a drawback for bad actors because it's still possible to track the requests and catch them as being suspicious. Now, to get around that, bad actors have started harvesting information server side by modifying core PHP files. In this case, the infection would be undetectable from the outside, but it's still going to be pretty easy to find because you're rarely modifying any of those core files, so any of those changes that are going to come up are going to be suspicious. To get around both of these drawbacks, we're seeing bad actors combine the two. So client side snippets of JavaScript are sending stolen credit card data to server side scripts that they've installed on the same server as the site. Now, this allows bad actors to cover their tracks a little bit because the traffic that's being redirected is going to the same server, and that's less likely to be flagged as suspicious. It's a bit more complicated to pull this off, but our team has been seeing this hybrid approach in the wild, so it's something to be on the lookout for. Now, another month has passed, and we found more cross site scripting attacks targeting WordPress plugins. Most notably, we discovered one that affects users of the YITH WooCommerce Ajax Product Filter plugin. Now, this is a plugin that allows WooCommerce stores to be filtered by product type, and it's pretty popular. It's got about 100,000 users right now, so with it being vulnerable, it's very important that all of them update to the latest version, which is 3.11.1. Some of the other plugins we found cross site scripting vulnerabilities with included Elementor Page Builder, Careerfy, JobSearch, and Newspaper. If you're looking for a full list of vulnerabilities that have been patched this month, John Castro at the Sucuri Labs blog has you covered. Check out our show notes for the link. Also, this month I had a blog go up detailing what's called a jibberish hack. It's basically the same motivation as an SEO spam attack where bad actors use your site's good standing to redirect visitors to their own sites. But in this attack, you'll find a bunch of randomly named folders filled with a ton of HTML files with really nonsensical file names like cheap-cool-hairstyles-photos.html. It's just going to be a mishmash of keywords that clearly you didn't put there. Unfortunately, just deleting all those HTML files and folders is not going to be enough to get rid of that jibberish hack though. You're going to need to fully clean any hacked files and database tables, and then you're going to have to deal with all the damage caused to your site's standing. And just keep in mind, if you find anything about that process too daunting, we're always here to help. Now, for this month's Sit Down, we have Sucuri analyst Krasimir Konov. Earlier in June, he had written a lab's note about a malicious downloader script that used the curl function, and we chatted a bit about it, but more importantly, we went really in-depth on all the different varieties of malware that website owners need to be aware of. But, before I get started with Krasimir, I just wanted to remind you about the Sucuri Sync-Up, our sister podcast. It's a weekly website security news briefing that you can find anywhere you get your podcasts, as well as the video version on our social media feed, and now you can even get it on your Amazon Alexa smart speakers. Just search Amazon skills for Sucuri Sync-Up, add the flash briefing, and get new content delivered every Monday. Now, on with the show. Hi Krasimir, thanks for joining us on the show. I thought we could start off and maybe have you tell us a little bit about yourself and what you do here at Sucuri? Krasimir Konov: Yeah, sure. Well, I joined Sucuri originally in 2014, but I've been in the IT business for about 10 years. Nine of those I did security. And currently at Sucuri I'm one of the malware analysts. I used to work in the front lines, used to clean websites and whatnot, and then I gradually moved up, and now I'm working in the malware research department. And my day to day job is basically analyzing malware, and then once I analyze it and figure out what it is, then I will create a signature for it. And we'll add those signatures to our tools, so we can automate some of the work we do. And I also write some Labs Notes blog posts. Usually, if I find something interesting in malware or some security topic, I'll write about it. Justin Channell: Yeah. And of those topics recently that you wrote about, one was about a malicious curl downloader, and how exactly did that work? Krasimir Konov: Right, yeah. That was an interesting one, but not very unique or anything like that. We see that a lot with curl being used as a downloader. It's a very common malware. So rather than including the actual malware in the file, the attackers would use curl to download the malicious code. In this case, they'll download it from Pastebin, but it could be anything. It could be another website or anything like that, and curl would just make a call to the website, request the code. The website will respond with the code, and then later on, there is some code to either save the output somewhere on the website, or you'll just run it through eval and execute the actual code right away. Justin Channell: Right. And you said that it's commonly found in malware, but let's kind of maybe talk a bit broader about malware in general. What is everything that is classified as malware? Krasimir Konov: Well, in general it will be anything that the owner of the website didn't authorize, anything that was added by a third party. There is a lot of different malware. It could be even something like a defacement that will also be considered malware because it was something the user did not authorize. Even though it might not be doing anything malicious on the website, it's not infecting users, the visit is still something they did not authorize. So defacement would also be considered malware. And even something like ransomware where the website is technically not really damaged, it's all encrypted, but it's not infecting anybody. It's not doing anything malicious, but it's still encrypting the entire website and asking the user or the customer, the owner of the website for a ransom they need to pay in order to get the website back online. Justin Channell: Okay. Let's maybe break it down to each individual type of malware. For example, what would be a way that maybe I-frames could be maliciously used by a hacker? Krasimir Konov: Yeah. An I-frame can be used maliciously when it loads content from another location. You can look at the I-frame as a window that just opens another website. So anything that website has on it, you're pretty much loading it through the I-frame. So if that website is infected and it's serving some kind of malware, by opening an I-frame, you're loading all those elements, everything that was on this website. And sometimes the I-frame can be as small as pixel or something hidden somewhere off the screen, so you wouldn't even know that it was opening it. Justin Channell: And yeah, I feel like we've also seen a lot of them where they're used almost to mimic popups as well. Krasimir Konov: Yeah. I mean the I-frame, it could just load from another website and the other website could do anything. It could be serving just malware and it would try to infect the user that doesn't even know that they're being connected to the other website. It could just have some other JavaScript that's just trying to open up pop ups on the original website through the I-frame. Yeah, it could be a lot of things. Justin Channell: Okay. And also, let's talk a little bit about conditional redirects and how those work. What allows a script to detect which devices are coming in and where they're coming from? Krasimir Konov: Right. Yeah. That's a common one we see a lot. Basically, a conditional redirect would be something, it's a redirect on the website. It's obviously malicious, but there's certain conditions that need to be met before the redirect is actually executed or the redirect happens. For example, let's say if it's on a phishing website or a phishing page that is hidden somewhere on the website. For example, if Google visits it, obviously the attacker doesn't want Google to see the actual phishing page and record it as a phishing page. So they'll look for, for example, the IP address. They would look for the user agent. And a lot of times they can tell that it's a bot. So they'll just return a 404 response, for example, that will be like, "Oh, page not found." So Google would be like, "Oh, it looks like this page doesn't exist." But then if a regular user goes to the same page, then those conditions will be met. The actual website or the script behind the phishing will check and see, and be like, "Oh, this one is running Firefox or Chrome," and be like, okay. And then they'll look at the IP and be like, "Oh, he's in whatever, he's in United States somewhere." And he's like, "Oh, okay. That's good." And then once all of these conditions are met, then the actual script will serve them the actual phishing page. And it'll be like, "Oh, you need to fill out this to recover your account or whatever, or type in your credentials to log in here." Justin Channell: And so this is the type of thing we're really, a website owner is going to run into this more commonly when people are complaining about they're getting served bad content or whatever, and they can't seem to replicate it. It's likely probably these kind of redirects. Is that right? Krasimir Konov: Right, right. It could be something as specific as, for example, a range of IP addresses that correspond to an ISP or maybe let's say a country. It could be like, "Oh, were targeting only customers in the US," so if you're connecting from another country and you go to the same website or the same page, it would just say 404. It will give you a page not found. But then if you actually have an IP address from the United States, you're connecting from the United States, then it will actually show you the phishing page. Justin Channell: Now another type of malware I feel like we see a lot here is SEO spam. We hear people talking about that. What are some of the top SEO spam keywords that you see coming through? Krasimir Konov: Yeah. We get that a lot. We see a lot of spam on websites. A lot of times attackers will use SEO spam to gain ranking for their own website. Or they'll just try to include some kind of SEO spam in links to another website that they're currently running or something. I mean, these things change all the time. So a website might be up for a week and then it'll disappear, and then they'll start another campaign. But yeah, we see that a lot. We see all kinds of keywords they use. Most common ones will be something like Viagra. We'll have like jerseys for sale. A lot of times, they'll use name brands like Nike, Rolex, Prada. We've seen even some essay writing services for some reason. I'm not sure why, but that's common. We see, for example, pharmaceuticals a lot that will use specific medicine names. They'll use all kinds of replicas, like a replica bag of this, replica this, replica that. We'd see prescription, also payday loans. And obviously there's some adult related sites and things like that keywords. Justin Channell: So pretty much anything that people are going to be searching and clicking on are probably going to be targets for SEO spam? Krasimir Konov: Right. I think a lot of it commonly is pharma related because a lot of people are looking to buy medicine online, and a lot of times will require a prescription. So a lot of people are like, "Oh, let me see if I can find this medicine that I can buy it online somewhere." They don't need a prescription. They don't want to pay to visit a doctor and whatnot, and they'll look for it. And yeah. Justin Channell: Now, whenever somebody's website does get hacked with a SEO spam attack, what kind of effect can it have on the website beyond just being defaced? Krasimir Konov: Yeah. You can have a lot of things can happen, negative things. For example, the website can be blacklisted because of the keywords. And that usually represents a big red warning when you go on the website, depending on who blacklisted it. But if it's Google, for example, you'll see a big warning and it'll tell you this website contains malware or there's something wrong with this website. So, pretty much all the traffic on the website will be gone. And then you can also lose a lot of your reputation if there is a SEO spam on the website. For example, if you were ranked in say number five for certain keywords that represent your product on Google search engines, and then suddenly you get hit with SEO spam, then all these search engines then go and visit the website. And all of a sudden they're like, "Oh, there's all these weird key words on here, all this SEO spam that's causing a lot of mixed signals." And the search engines are like, "Oh, where do we rank this website now? Do we rank them with this product that's originally what the website is about? Or do we take into consideration all these other keywords that are mixed up that are SEO spam?" So, all of a sudden your website might go from being ranked number five on the first page to being on the 10th page. And then you rank for all these other keywords that you didn't intend to. And then people search for something completely different. They're searching for jerseys or something, or now they're searching for Prada products, and then suddenly your website pops up in there. So you're not really getting any good traffic, not targeted traffic. But, yeah. Justin Channell: Okay. So in a lot of ways, the effects of SEO spam would kind of be the same for defacements or any kind of malware with the blacklisting, but it does bring that kind of unique part to it where then it can also then bring traffic that you weren't expecting from somebody searching for jerseys, for example. I had not really ever thought about that. Krasimir Konov: Right, right. Yeah. It will definitely bring some traffic. I've seen a lot of times where websites will be connected. Let's say, there was 1,000 websites that were all infected with SEO spam, and it will kind of link each other to try to bring each other up into the rankings. And so you would see a lot of strange traffic from some random websites that were, for example, that were previously infected, even if they might not be anymore. But yeah, they'll be sending traffic to you or there'll be usually search engines sending you traffic, but for the wrong keywords. People are looking for something else, so obviously they're not going to be interested in your website. They're not going to buy anything because they're not looking for that. Justin Channell: And now, so thinking of the way websites get infected, a very common way it seems to be is through phishing campaigns. What are some recommendations you have for the best ways to avoid becoming a phishing victim? Krasimir Konov: Yeah. There is some ways. I mean, it depends really on the type of attack. Obviously, a lot of people, when they think of phishing, they think, "Oh, it's just like a PayPal phishing page and it just looks like the original," but it could be more subtle. If it's just a regular page where you're just going and you get redirected to another website, obviously the first thing to look is if you have the security padlocks, make sure that traffic is encrypted. A lot of these websites don't really have any encryption nowadays. More are starting to get that with pre SSLs being issued and whatnot. But that's the first thing to look and see, make sure. Anywhere you're typing your sensitive information, you want to make sure you have the padlock to make sure everything is encrypted. Krasimir Konov: But also you want to look at the URL of the actual website you're visiting. A lot of times they'll try to hide it. So you might have to be careful and look closely. Something that might be an I will be an L or something like that. And a capital I and L might look kind of similar into your IRL, so you might miss something like that. Say, if you're looking for PayPal and it might replace the L with an I, and if you don't look closely, it might look exactly the same. And you're like, "Oh, okay, it's paypal.com," but not really. So yeah. Just pay attention to the URL, make sure it is the actual website. There's no paypal.com dot something, dot something else, dot com. Yeah. You want it to just say paypal.com, and then it'll have forward slash and something else. But yeah, it gets more complicated when you have, for example, a phishing page that's injected into a regular page. For example, you have a checkout page on a website that you're buying things from and you go through the checkout page and you're looking at where you type in your credit card information and whatnot. And you might have a phishing page that actually looks exactly like a little box that gives you where you put in your credit card number, or your name, your address, and all that. So that will be more subtle. For example, that could be also an I-frame that's just coming from another page. And it will look exactly like it's part of the website. You're on the legitimate website, but only that portion of the website is actually the phishing page. And you look at it and you're like, "Oh, okay. It looks fine. I'm just putting my credentials." So that one could be a lot harder to figure it out. Usually, if it's something like that, I look for something that looks kind of out of place. Maybe they didn't get the right font. It might not be the same as the original website or there might be something out of place, some fields that are missing or some fields that are squished into the left or the right. It looks kind of awkward. It's like, why would this be like this? The whole website looks professional. There's a pink background or something, for example, and then suddenly there's this white box in the middle. It's like, ah, it looks kind of weird, out of place. Justin Channell: So pretty much if anything looks slightly out of place, you really should double check everything at that point. Krasimir Konov: Right. Right. Yeah. Obviously there's more ways that you can check, but I wouldn't get into more technical, like inspecting elements and looking at stuff, but yeah. Justin Channell: And now another type of malware that's kind of, and it kind of plays in with whatever the other infection is, is backdoors. Can you give us some examples of what backdoors can be? It's mainly just when a hacker can get back into the site to reinfect it, but I know there are a ton of different methods. And what are some of the more common ones and then maybe some that really interesting that you've seen? Krasimir Konov: Yeah, there is a lot. They'll probably be one of the first things the hacker would do is if they compromise a website, obviously they'll try to spread backdoors and just inject code everywhere so they can get back in, even if the owner of the website or webmaster cleans it. They want to try and hide some malicious code somewhere so they can always get back in. There's many variations. A backdoor could be something as simple as a single line of code to just [inaudible 00:20:19] argument, some kind of string or something via get or post. Krasimir Konov: And then it runs into an eval, so it evaluates the code and executes it. And some backdoors are very complex and they can be included in, let's say you have a WordPress site and you have a specific login page where all the login credentials are being processed and everything else. They could even inject code into that to basically bypass the whole login mechanism so that they can just bypass everything. They don't even have to know any user. They don't have to know the password, nothing. They'll just include some lines in there, and every time they'll be just able to log in. Yeah. It gets pretty crazy. Yeah. I mean, there's all kinds of malware. There is always a malware, for example, that just targets credit cards and will just target the eCommerce websites. And they'll just try to steal the login credentials, I mean, the credit cards. They'll try to get your address, your credit card information, any kind of CVV code or whatever you typed into the billing address, everything. And then there's also malware like the backdoors that are just trying to keep the attacker in control and trying to get them back into the website. There's just so many variations of what a malicious user might want to do on a website. Some can be something as simple as just reinfecting the website. They don't want to keep control. They just want to keep reinfecting it with some kind of malware. So even if you clean it, it would just get reinfected. Some of them in the database, otherwise might be in the files. We've seen some added into a [inaudible 00:22:14] job that just keeps running on the server. There could be malware that is just a giant to, for example, attack out of websites. Like for example, a distributed denial service where they put the same malware on thousands of websites. And then they try to send traffic to one website to try to bring it down. Yeah. People try to do all kinds of stuff with websites. We've seen even some cryptocurrency mining malware that you go onto a website and suddenly your PC starts running like crazy. And you're like, what the hell is going on? Your fans turn on and the PC is 100% CPU. And it turns out that the website has some malware that's just by mining Bitcoins with your CPU and it's using all of it. Justin Channell: Wow. Okay. So one question now, the last question I have is of all the malware that you've seen, what do you think is the coolest piece of malware that you've ever seen? Krasimir Konov: I think the coolest would be the ones that are so subtle that you don't even know that it's there. For example, we've seen some that were pretty innovative. It will be just a one liner code that's just one line. And for example, it will be let's say 40-50 characters, something like that. And that's all it is. And they'll hide it somewhere in between the legitimate code. And if you don't know what you're looking for, you would never see it. It doesn't look suspicious. There is no links to some other website. There's no some kind of encrypted code or anything like that. It's just a simple one line. And then if you're just scrolling through the file looking for something, you would never see it. It just looks like all the other code. And then if you look closely, you're like, "Oh, there's this..." Look closely, and you're like, "Oh wow, this is not supposed to be there." And then you keep looking at it and you're like, "This looks really weird." And then you see that it's actually doing some malicious things and trying to evaluate some code or taking output from the outside, I mean, some input from outside, you can call it and give it code to run. Justin Channell: Well, Krasimir, thanks for coming on and talking to us for today. Krasimir Konov: Yeah. Thank you. Thank you. I'm so happy. I'm glad I was able to do this podcast and I can't wait to do another one. Justin Channell: Yeah, we'll have you on again. Thanks. Krasimir Konov: Thank you. Justin Channell: Thanks again to Krasimir for joining us here on the Sit Down. We'll be back with another episode next month. So be sure to subscribe on Apple podcasts, Spotify, Stitcher, or any podcasting platform. Also, be sure to follow us on social media at Sucuri Security and check us out at sucuri.net. That's S-U-C-U-R-I.net. I'm Justin Channell, And this has been the Sucuri Sit Down. Stay safe out there.](https://blog.sucuri.net/wp-content/uploads/2020/05/20-sucuri-podcast-blog-post_blog_image-390x183.jpg)



