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Yesterday I was setting up my new windows laptop and while browsing on Firefox I got a webpage saying "urgent Firefox update is available" and I accidentally executed it.
I immediately realised that it was a malware and immediately uninstalled Firefox. I had my Facebook and Gmail logged in on Firefox and have since changed their passwords.

Is there anything else that I should be concerned about?

It is a brand new laptop so I don't have any personal data on it. So that is not a worry.

On a side note, when I installed Firefox back, I was already logged into FB and Gmail. I am not sure if it is because of the malware.

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    Change the passwords you saved in any application. Change them on any other environment where you used the same passwords. If you have online backups, check them. A reinstall is an heavy task and far from sufficient, something of a sadistic approach which make you lose any chance to understand and progress. – dan Aug 17 '16 at 6:54
  • @danielAzuelos that's my exact purpose!! I want to learn about the impact or know how to understand the impact! – Limit Aug 17 '16 at 12:24
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If it is a brand new laptop I would just reinstall the OS.

The malware that you executed will not be fixed by removing Firefox. If your computer had more time invested in it, it may of been worth while trying various malware/virus detection/removal products. But as it is brand new just reinstall the operating system.

As for what effect it could have, did it prompt to "make changes to your computer"? If yes and you clicked yes, then the malware could do almost anything, from installing new software, to modifying the operating system, to installing device drivers.

The most common thing for malware to do is to install something that autostarts and contacts another computer and requests instructions. These instructions are normally either to be part of a botnet, being part of a DDoS attack, sending spam emails, clicking on ads on webpages. Or installing crypto-locker which would encrypt all your files on your computer and demand money to decrypt. There are lots of other things this could do, these are just some examples.

  • Being a student, I'm also interested in finding out the extent or suggestions on how to find out the impact. Can you help me with that? – Limit Aug 17 '16 at 11:28
  • answer edited with some examples of what it could do – David Waters Aug 18 '16 at 21:08
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  1. I suggest you to run Malwarebytes, and suppress the identified malware.

    I bet it will find a Javascript downloader, which will be identified as a Trojan horse.

    Feel free to test any other malware detection software, since you will never be in such a freedom to experiment.

  2. Once removed from your disk, take care to remove it also of all your backups online at the time of the suspected impact (a few seconds before the false update window).

  3. Read the available documentation about this Trojan horse, and if you discover it is fired by any specific piece of software, for example Adobe Flash Player, verify you have a version updated of all the security vulnerabilities.

    I bet your malware was coming from a vulnerable Adobe Flash Player. That's an easy bet, Adobe is one of the leader in this field.

  4. Once badware upgraded, change your password within any application you trusted to keep it on this PC. Because all these applications (for example Outlook) display you a nice •••••••• when you register your password, but they keep it in clear text format because this is the format they need to provide it in your place. And all the malware know where to collect them in clear.

  5. Since you are pretty sure that your passwords are now owned by criminals, you have to change them on any other server where you were using the same ones. Take advantage of this small nightmare to choose different passwords on different servers so as to avoid to play the same sadistic horror cleaning twice.

Notes

I have no evidence you need to reinstall Firefox (because I bet that this software wasn't the entry point of the malware). Then don't do it if it isn't necessary (step 3.). You already have enough sadistic cleaning to do thus far.

To reinstall Windows won't fix all the damages made by a malware. Then the time investment on this sadistic task is rarely appropriate. It is a religious procedure sold by many support teams to the dummies. To be honnest, I don't like this religion. For me its the "baseball bate to smash the mosquitoes" of the information security market.

  • "To reinstall Windows won't fix all the damages made by a malware". What are you talking about? Of course reinstalling windows will fix the issue or at least more likely to fix the issue. Reinstalling windows = reformat your drive and re-install windows. Unless the malware hacked your bios or your recovery partition this will entire eradicate the malware – gman May 19 '18 at 3:40
  • I am thinking here to what most malware do: they don’t politely stop their impact at the frontier of the OS. Most of malwares impact user space and neighbour computers. Considering only the first of these collateral damages, once a cold reinstall of Windows has been performed, a Windows system is of course clean. But to make real work, its owner will immediately restore all user space files, and the malware will be restored too (e.g. within a PDF, Word file, within a Javascript downloader which will be in the Internet Explorer history…). – dan May 23 '18 at 6:24

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