You load your own site, and instead of your homepage you get a blank page with a line of text reading 500 Internal Server Error. No explanation, no stack trace, nothing to act on. For visitors, it looks like the site is simply gone, and for you it usually means the admin area is down too, so the one tool you’d normally reach for is unavailable.
The frustrating part is that a 500 is deliberately vague. It’s the server’s way of saying “something broke while I was handling your request, and I’m not going to tell you what.” The real detail exists, but it lives in your error log, not on the page your visitors see.
In this guide, we’ll explain what a 500 error actually is, what causes it most often, how to work through the fix in a sensible order, and the part most troubleshooting guides skip: how to tell when a 500 is a symptom of a compromised website rather than a simple configuration mistake.
Contents:
- What is a 500 internal server error?
- What does a 500 error look like on your site?
- What causes a 500 internal server error?
- Is a 500 error the website’s fault or my browser’s?
- How to fix a 500 internal server error, step by step
- How do you fix a 500 internal server error in WordPress?
- Can a hacked website cause a 500 error?
- Does a 500 error hurt SEO and visitors?
- How to reduce 500 errors going forward
- Wrapping up
- Frequently asked questions
What is a 500 internal server error?
A 500 internal server error is an HTTP status code the server returns when it encounters an unexpected condition that stops it from completing the request. That’s the whole definition, and it’s intentionally broad. The 5xx family means the problem is on the server side; the 500 specifically means the server couldn’t categorize the failure any further.
Compare that to its neighbors. A 502 means one server got a bad response from another server upstream, a 503 means the service is unavailable or overloaded, and a 504 means something upstream timed out. Those at least point you in a direction. A 500 doesn’t, it’s the catch-all.
It also helps to know what a 500 is not. It isn’t a browser problem, and it isn’t a DNS or network problem. The request reached your server and your server tried to answer it. Something in the middle of that attempt- maybe PHP, a configuration directive, a permission, or a database call, failed hard enough that there was no usable response to send back.
What does a 500 error look like on your site?
The wording changes depending on the web server, the host, and whether your application managed to render anything before it gave up. You may see any of these:
- 500 Internal Server Error
- HTTP Error 500
- HTTP 500 – Internal Server Error
- Internal Server Error. The server encountered an internal error or misconfiguration and was unable to complete your request
- A completely blank white page
- “There has been a critical error on this website” in WordPress
That last one matters. WordPress will sometimes catch a fatal PHP error and show its own message instead of letting the raw 500 through, which is friendlier but hides the status code. If that’s what you’re looking at, our walkthrough of “There Has Been a Critical Error on This Website” covers the same underlying failure from the WordPress side.
A blank page with no text at all is also commonly a 500, the server returned the status code but no body. Check the status code in your browser’s developer tools (the Network tab) or with a command-line request so you know what you’re actually dealing with.
What causes a 500 internal server error?
Almost every 500 traces back to one of a handful of causes. Here they are, roughly in the order we see them cause trouble on real sites.
A faulty plugin, extension, or theme. A plugin update introduces code your PHP version can’t run, two plugins define the same function, or a theme file calls something that no longer exists. PHP throws a fatal error, and a fatal error with nothing to catch it becomes a 500.
A corrupt or conflicting .htaccess file. On Apache, .htaccess controls rewrites, redirects, and various per-directory settings. One invalid directive, a typo, a rule copied from a different server, a PHP setting your host doesn’t allow to be set there, is enough to take down every URL under that directory.
PHP memory exhaustion or a PHP version mismatch. A script that needs more memory than the limit allows will die mid-request. So will code written for a different PHP version than the one your host is now running, which is a very common outcome after a host-initiated PHP upgrade.
Wrong file or directory permissions. If the web server can’t read a file it needs, or if a file or folder is set to permissions the server refuses to execute from, the request fails. Overly permissive settings cause the same result on hardened hosts, which surprises people.
A failing script or external dependency. A cron job, a custom integration, or an API call that hangs or returns garbage can produce an unhandled error. Database connection failures often surface as a 500 as well.
Something malicious. Injected PHP and modified .htaccess rules are two of the most common things attackers leave behind, and both can break a site outright. We’ll come back to this below because the troubleshooting path is different.
Is a 500 error the website’s fault or my browser’s?
It’s the website’s. A 500 is generated by the server, so the fix has to happen on the server or in the site’s code and configuration. No amount of clearing your browser cache will resolve a genuine 500.
That said, two things are worth ruling out before you start digging, because they take seconds. First, reload the page once. If an error was momentary (a brief resource spike, a dependency that recovered), it won’t repeat. Second, check the site from another network or device, or from an outside status-checking service. If it fails for everyone, it’s the server. If it fails only for you, you may be hitting a cached error response or a stale entry at a CDN or proxy layer, and purging that cache is the fix.
If the page loads for you but not for your visitors, you may be looking at a different problem entirely, something closer to the territory covered in “This Site Can’t Be Reached”.
How to fix a 500 internal server error, step by step
Work through these in order. The sequence is deliberate. It starts with the step that tells you the actual cause, then moves through the causes by how often they’re responsible.
- Read your server’s error log – This is the single most valuable step, and it’s the one people skip. The log will usually name the file and line number that failed. Find it in your hosting control panel (often labeled “Error Log” or “Logs”), or at the path your host documents for Apache, Nginx, or PHP-FPM error logs. Our piece on website and server logs explains what’s in each type and why keeping them accessible matters.
- Turn on application-level debug logging – If the server log is unhelpful, enable your platform’s own error logging so PHP notices and fatal errors get written to a file rather than discarded. In WordPress that means setting the debug and debug-log constants in
wp-config.php. Log to a file andnd never display errors on screen on a live site, since error output can expose paths and other internals to anyone who triggers it. - Rule out
.htaccess– Rename.htaccessto.htaccess_oldand reload the site. If the error clears, the file was the problem. On WordPress, re-save your permalink settings to generate a clean one. On other platforms, re-add directives a few at a time until the error returns so you know which one broke it. - Deactivate plugins and switch to a default theme – If you can reach the admin area, deactivate all plugins, confirm the site loads, then reactivate one at a time. If you’re locked out, rename the plugins directory over SFTP to disable everything at once, then rename it back and disable individual plugin folders. Do the same with your active theme by temporarily switching to a default one.
- Raise the PHP memory limit – If the log mentions allowed memory size being exhausted, increase memory_limit through your host’s PHP settings panel, ini, or
wp-config.php. Treat this as a diagnostic, not a cure. If a plugin needs far more memory than the rest of your site combined, that plugin is the real issue. - Check which PHP version you’re running – If the error started right after a host-side upgrade (or right after you changed versions yourself), switch back temporarily to confirm that’s the cause, then update the code that can’t run on the new version. Staying on an unsupported PHP version indefinitely is its own risk, so treat the rollback as a window to fix things.
- Verify file and directory permissions and ownership – On most shared hosts, files are expected at 644 and directories at 755, with everything owned by your hosting account’s user. A file sitting at 777, or owned by a user the web server doesn’t recognize, is both a functional problem and a security problem worth looking into.
- Look at what changed recently – Check the modification times on your core, theme, and plugin files. A 500 that starts with no deployment, no update, and no configuration change on your part is a strong hint that something modified your files without you (see the next step).
- Clear every cache in the chain – Purge your page cache, object cache, CDN, and any reverse proxy. Caches can hold a 500 response and keep serving it after the underlying fault is fixed.
- Ask your host – If the log points at something outside your control, like a resource limit, a failing database server, a server-level module, your host can see layers you can’t. Give them the exact timestamp and the log line; it saves a round trip.
Before you change anything, take a full backup of files and database. Troubleshooting a 500 involves renaming and editing files that your site depends on, and you want a way back.
How do you fix a 500 internal server error in WordPress?
The order above still applies, but WordPress gives you a few extra places to look and a few extra ways in when the dashboard is unreachable.
Start by enabling debug logging in wp-config.php so fatal errors land in a log file inside wp-content instead of vanishing. Then disable plugins by renaming the wp-content/plugins folder over SFTP. WordPress will load with everything off, and if the site comes back you’ve confirmed a plugin is at fault. Rename the folder back, then rename individual plugin directories one by one to find the culprit.
If plugins aren’t it, switch themes the same way by renaming your active theme’s folder, which forces WordPress to fall back to a default theme. After that, regenerate .htaccess by deleting (or renaming) it and re-saving Settings → Permalinks once you have admin access again.
Two WordPress-specific causes are worth checking directly. Corrupted core files can be fixed by re-uploading a fresh copy of WordPress over SFTP, excluding wp-content and wp-config.php. And a failed or interrupted update can leave a .maintenance file in the site root. Deleting it releases the site.
If you’d rather not poke at a live site blind, do this work on a staging copy where enabling verbose errors carries no risk.
Can a hacked website cause a 500 error?
Yes, and this is the part generic troubleshooting guides tend to leave out. Malicious code is still code, and badly written or environment-mismatched malicious code breaks sites the same way a buggy plugin does.
We see a few patterns regularly. Injected PHP at the top of index.php, wp-config.php, or a theme’s functions.php can throw a fatal error, sometimes immediately, sometimes only after the host changes PHP versions and the injected code stops being valid. A modified .htaccess is just as common. Attackers add redirect rules, conditional directives keyed to user agent or referrer, or php_value and auto_prepend_file directives that the server rejects, and the whole directory tree starts returning 500s. Backdoors left behind after a cleanup, or a partially removed infection, can break things too. Half a function is worse than all of it.
A few signals suggest you’re looking at a compromise rather than a configuration mistake:
- The error appeared with no update, deployment, or settings change on your side.
- File modification timestamps on core, theme, or plugin files are recent and unexplained.
- The 500 only happens for some visitors, some user agents, or visitors arriving from search (cloaked malware often behaves conditionally).
- You find unfamiliar files, or
.htaccessfiles in directories that shouldn’t have one. - Your error log names a file or function you don’t recognize and can’t trace to anything you installed.
None of these is proof on its own. A recent timestamp can come from a legitimate automatic update, and conditional behavior can come from caching. But when the error log points at code you never wrote, stop troubleshooting and start investigating.
The practical move is to run a server-side scan or file integrity check that compares your core files against known-good versions, review .htaccess in every directory (not just the root), check for recently added admin users, and look at access logs around the timestamp of the first 500. If you do find an infection, clean the files, change every credential such as hosting, SFTP, database, and CMS admin, and then patch whatever let the attacker in, because restoring a clean backup over an unpatched vulnerability just resets the clock.
Does a 500 error hurt SEO and visitors?
A brief 500 that you catch and fix within minutes is unlikely to cause lasting damage. Search crawlers encounter transient server errors all the time and will generally come back and try again, which is exactly why 500 is a server-error code and not a “remove this page” instruction.
Sustained 500s are a different story. If crawlers keep hitting errors over days, affected URLs can drop out of the index, crawl frequency can fall, and depending on how your site is configured, error responses may get cached and served to real people long after you think you’ve fixed things. The business cost usually arrives before the search cost. A checkout that returns a 500 doesn’t convert, and a visitor who sees a server error rarely tries again.
So the goal isn’t only to clear the error, it’s to find out quickly when one appears. Uptime monitoring that alerts on 5xx responses, and a habit of actually reading your error logs, turn a multi-day outage into a short one. If you use Google Search Console, keep an eye on the server-error reports there as a second pair of eyes on crawler-visible failures.
How to reduce 500 errors going forward
Most 500s are preventable, and the preventive habits are unglamorous. Update plugins, themes, and PHP on a staging copy before production, one change at a time, so when something breaks you already know what caused it. Keep automated backups you’ve actually tested restoring.
Keep your error logs turned on and reachable. The difference between a ten-minute fix and an afternoon of guesswork is almost always whether you could read the log line that named the failing file.
Tighten the basics that double as both stability and security measures. Use sane file permissions, no world-writable directories, unique strong credentials for hosting and admin accounts, and as few plugins as you genuinely need. Fewer moving parts means fewer things that can throw a fatal error.
And treat unexplained 500s as worth a second look rather than a reload. A 500 you can’t account for is one of the clearer invitations to check your site’s integrity. See our guide to HTTP error 403 for a related status code that malware sometimes produces in the same way.
Wrapping up
A 500 internal server error tells you that your server failed, not why. Everything useful lives one layer down in the error log, and the fastest path through the problem is to read that log first and only then start renaming .htaccess, disabling plugins, and adjusting PHP settings.
Keep the second question in mind as you work. If nothing you did explains the failure and the log points at code you don’t recognize, you may be fixing the symptom of a compromise rather than a bug. Checking that early costs you a few minutes and can save you from cleaning the same site twice.
Frequently asked questions
What causes a 500 internal server error?
Most 500 errors come from a faulty plugin, extension, or theme, a corrupt .htaccess file, PHP memory exhaustion or a PHP version mismatch, incorrect file and directory permissions, or a script or database call that fails mid-request. Injected malicious code and malware-modified .htaccess rules can cause the same failure.
Is a 500 error the website’s fault or my browser’s?
It’s the website’s. A 500 is generated by the server after your request reaches it, so clearing your browser cache won’t help. The exception worth checking: a cached 500 response at a CDN, proxy, or page cache can keep showing the error after the real cause is fixed, so purge those caches.
Can a hacked website cause a 500 error?
Yes. Injected PHP in files like index.php or functions.php can throw a fatal error, and malware-modified .htaccess directives can break every URL in a directory. Treat a 500 that appeared with no update or change on your side, or that names unfamiliar code in your log, as worth investigating.
Does a 500 error hurt SEO?
A short-lived 500 usually doesn’t cause lasting harm, since crawlers retry server errors. Sustained errors are riskier: affected URLs can drop from the index and crawl rates can fall. Monitor for 5xx responses so outages stay short, and watch server-error reports in Google Search Console.
How do I find out what’s actually causing my 500 error?
Read your server’s error log, available in your hosting control panel or at the path your host documents for Apache, Nginx, or PHP-FPM. It usually names the failing file and line number. If it’s unhelpful, enable your application’s own debug logging to a file. Never display errors on a live site.
How is a 500 error different from a 502, 503, or 504?
All four are server-side errors. A 500 is the generic catch-all: the server failed and couldn’t categorize why. A 502 means a bad response from an upstream server, a 503 means the service is unavailable or overloaded, and a 504 means an upstream request timed out.
Matt Morrow![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)
Justin Channell
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