HTML/Brocoiner found in Firefox cache. What to do?
A few days ago, Windows Defender started finding HTML/Brocoiner!frn on my main computer. It always found it in the Firefox cache. I was getting the warning every few minutes while connected to the Internet. The warnings stopped when I unplugged the network cable and resumed when I plugged it back in. I have several computers on my network and an extensive scan of each with the same Windows Defender found nothing. I wiped the infected computer clean and spent the better part of a day rebuilding it. I used the Microsoft Media Creation tool to download a clean Win10 Pro onto a memory stick. Imagine my surprise when, the following day I did another full scan on the computer and found another instance of HTML/Brocoiner!frn in the Firefox cache. Again I scanned the other computers on the network and again found nothing. I immediately removed Firefox from the computer, making sure that the Mozilla Maintenance Service was also uninstalled. Then I scanned the folder 'C:\Users\HealthyPhil\AppData\Local\Mozilla and deleted it. So currently, I've decided to go ahead without my favorite browser, putting up with Edge instead. Does anyone know anything more about this issue? Could Windows Defender be reporting a 'false positive' - mistaking something legitimate the latest Firefox is doing for this Trojan? !!!! Disturbing thing !!!! After writing this post I clicked on the 'Automatically Add' button below. It took me straight to a Firefox page saying it couldn't find the link. Of course, it wiped out my whole post at the same time! Luckily, as a seasoned computer person, I had already copied the post into a temporary Notepad text file before clicking on the button!
Όλες οι απαντήσεις (9)
Hello, Ublock Origin for Firefox blocks bitcoin miners embedded in Websites. https://addons.mozilla.org/en-US/firefox/addon/ublock-origin/
To clear Firefox Cache:
- Click the menu button
, choose Library, and then click on History, and select "Clear Recent History...".
- Under "Time range to clear", select "Everything".
- Now, click the arrow next to Details to toggle the Details list active.
- From the details list, check Cache and Cookies and uncheck everything else.
- Now click the "Clear Now" button.
Further information can be found in the Delete browsing, search and download history on Firefox article.
Did this fix your problems? Please report back to us!
Thank you.
Τροποποιήθηκε στις από τον/την Mkll
Hi, Mkll - thanks for your speedy reply. Yes, I did this. I clear my Firefox cache on a regular basis. When this was happening - I went in and cleared EVERYTHING, all boxes ticked. It made no difference whatsoever. Windows Defender continued to pop up a new instance of this Trojan at the same rate (about once every 3 minutes or so). Thinking back, it didn't matter if Firefox was open or not, the instances kept going constantly so long as the computer was on and connected to the Internet. But they were in the Firefox cache! But so far, on the rebuilt system, I've only had the single instance, yesterday. As I said, I completely uninstalled Firefox and deleted the Mozilla folder under ..appdata\local. Since then I've had no issue. But time will tell whether that continues.
Mkll said Sorry, nothing more to add. Created this by mistake and don't know how to delete it (I'm new to this forum).
Τροποποιήθηκε στις από τον/την HealthyPhil
Did Ublock Origin fix it?
Mkll said
Did Ublock Origin fix it?
Not yet. I haven't re-installed Firefox yet. I'll do that and if UBlock fixes the issue I'll install it in Firefox on my other computers, too. Thanks muchly! I'll consider this tentatively resolved but I won't mark it as resolved until it's been running a few days Cheers (and Merry Christmas)
This KB article is no longer maintained but the information may still be useful: Firefox cache file was infected with a virus
A similar question was posted a few days ago at reddit, in case it helps ("Trojan:HTML/Brocoiner!rfn" found by Windows Defender in Firefox cache) : https://www.reddit.com/r/computer_help/comments/7icdu3/virus_help/
You can also run www.malwarebytes.org/
Malwarebytes - Thanks, Tyler. I'll check it out.
AliceWyman said
This KB article is no longer maintained but the information may still be useful: Firefox cache file was infected with a virus A similar question was posted a few days ago at reddit, in case it helps ("Trojan:HTML/Brocoiner!rfn" found by Windows Defender in Firefox cache) : https://www.reddit.com/r/computer_help/comments/7icdu3/virus_help/
Thanks, Alice. I found those posts on Reddit while I was searching for help on the issue. And thanks for the old Firefox cache page, too. I've just re-installed Firefox again and activated the UBlock Origin plug-in as recommended by Mkll. We'll see how it goes. I'm not going to make Firefox my default for now. I'll stick with Edge until I'm sure the problem's disappeared. I'm using Firefox and doing a quick scan with Windows Defender every couple of hours. Then I'll do a full scan every evening, too. If everything's clean in a couple of days, I'll come back and mark this problem as solved. I'm not convinced it was actually a Firefox-related issue. Windows Defender kept finding instances of the Trojan popping up every couple of minutes, even when the computer was just sitting with no apps running. I'm wondering if the Trojan was just using the Mozilla cache as an extra level of cover to hide what it was doing.
Τροποποιήθηκε στις από τον/την HealthyPhil