Today, somebody had a problem: they kept seeing a popup on their screen, and obvious scam trying to sell them McAfee anti-virus. Where was this coming from?
In this blogpost, I follow this rabbit hole on down. It starts with "search engine optimization" links and leads to an entire industry of tricks, scams, exploiting popups, trying to infect your machine with viruses, and stealing emails or credit card numbers.
Evidence of the attack first appeared with occasional popups like the following. The popup isn't part of any webpage.
This is obviously a trick. But from where? How did it "get on the machine"?
There's lots of possible answers. But the most obvious answer (to most people), that your machine is infected with a virus, is likely wrong. Viruses are generally silent, doing evil things in the background. When you see something like this, you aren't infected ... yet.
Instead, things popping with warnings is almost entirely due to evil websites. But that's confusing, since this popup doesn't appear within a web page. It's off to one side of the screen, nowhere near the web browser.
Moreover, we spent some time diagnosing this. We restarted the webbrowser in "troubleshooting mode" with all extensions disabled and went to a clean website like Twitter. The popup still kept happening.
As it turns out, he had another windows with Firefox running under a different profile. So while he cleaned out everything in this one profile, he wasn't aware the other one was still running
This happens a lot in investigations. We first rule out the obvious things, and then struggle to find the less obvious explanation -- when it was the obvious thing all along.
In this case, the reason the popup wasn't attached to a browser window is because it's a new type of popup notification that's suppose to act more like an app and less like a web page. It has a hidden web page underneath called a "service worker", so the popups keep happening when you think the webpage is closed.
Once we figured the mistake of the other Firefox profile, we quickly tracked this down and saw that indeed, it was in the Notification list with Permissions set to Allow. Simply changing this solved the problem.
Note that the above picture of the popup has a little wheel in the lower right. We are taught not to click on dangerous thing, so the user in this case was avoiding it. However, had the user clicked on it, it would've led him straight here to the solution. I can't recommend you click on such a thing and trust it, because that means in the future, malicious tricks will contain such safe looking icons that aren't so safe.
Anyway, the next question is: which website did this come from?
The answer is Google.
In the news today was the story of the Michigan guys who tried to kidnap the governor. The user googled "attempted kidnap sentencing guidelines". This search produced a page with the following top result:
Google labels this a "featured snippet". This isn't an advertisement, not a "promoted" result. But it's a link that Google's algorithms thinks is somehow more worthy than the rest.
But where is the text I was promised in the Google's search result? It's there, behind the image. PDF files have layers. You can put images on top that hides the text underneath. Humans only see the top layer, but google's indexing spiders see all the layers, and will index the hidden text. You can verify this by downloading the PDF and using tools to examine the raw text:
If you click on the "I am not robot" in the fake PDF, it takes you to a page like the following:
Here's where the "hack" happened. The user misclicked on "Allow" instead of "Block" -- accidentally. Once they did that, popups started happening, even when this window appeared to go away.
As described above, once we identified this problem, we were able to safely turn off the popups by going to Firefox's "Notification Permissions".
Note that the screenshots above are a mixture of Firefox images from the original user, and pictures of Chrome where I tried to replicate the attack in one of my browsers. I didn't succeed -- I still haven't been able to get any popups appearing on my computer.
So I tried a bunch of different browsers: Firefox, Chrome, and Brave on both Windows and macOS.
Each browser produced a different result, a sort of A/B testing based on the User-Agent (the string sent to webservers that identifies which browser you are using). Sometime following the hostile link from that PDF attempted to install a popup script in our original example, but sometimes it tried something else.
For example, on my Firefox, it tried to download a ZIP file containing a virus:
When I attempt to download, Firefox tells me it's a virus -- probably because Firefox knows the site where it came from is evil.
So I opened the password file to get the password ("257048169") and extracted the virus. This is mostly safe -- as long as I don't run it. Viruses are harmless sitting on your machine as long as they aren't running. I say "mostly" because even for experts, "misclicks happen", and if I'm not careful, I may infect my machine.
You can go investigate on VirusTotal other things it found with this virus.
Viruses and disconnected popups wasn't the only trick. In yet another attempt with web browsers, the hostile site attempt to open lots and lots of windows full of advertising. This is a direct way they earn money -- hacking the advertising companies rather than hacking you.
In yet another attempt with another browser, this time from my MacBook air, it asked for an email address:
- somebody skilled at SEO optimization, who sends links to a broker
- a broker who then forwards those links to other middlemen
- middlemen who then deliver those links to sites like AppCine.net that actually ask for an email address or credit card
- popups pretending to be anti-virus warnings that show up outside the browser
- actual virus downloads in encrypted zips that try to evade anti-virus, but not well
- endless new windows selling you advertising
- steal your email address and password, hoping that you've simply reused one from legitimate websites, like Gmail or your bank
- signups for free movie websites that try to get your credit card and charge you legally
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