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Danger level 7
Type: Adware
Common infection symptoms:
  • Annoying Pop-up's
  • Shows commercial adverts
  • Connects to the internet without permission


CoronaBorealis seems to be a new useless adware program that is a clone of Canopus and Capricornus. So, if you notice “ads by CoronaBorealis” labels while you are browsing the web, you need to know that your computer may have been infected with this malware. We have discovered that even if you have CoronaBorealis adware on your system, it is still possible to see “ads by Capricornus” labels on third-party ads. In any case, if you have this adware infection on board, you need to act before you are exposed to potentially harmful third-party web content. We advise you to remove CoronaBorealis because this infection poses a threat to your system security, not to mention that it may not even be alone. In order to be able to step up against this threat, you need to understand the risks it may represent to you and your computer as well as how you could protect your PC from similar invasions.

As our research shows, this adware application cannot be found as a standalone installer, we have found no official, promotional website. Instead, we have come across free software bundles that not only contained CoronaBorealis, but also some other malware infections. So, if you have noticed annoying third-party ads while you were surfing the web, you need to scan your computer to identify all malware infections as long as you want to restore the previous security level. You can try to find malware applications by going through the installed programs list in Control Panel, or the extension lists in your browsers.

However, that way you could most likely spot adware programs, browser hijackers, and potentially unwanted programs. But there are much more dangerous infections out there, such as Ransomware programs, Trojans, and Rootkits, which all hide deep in your operating system. It would take an expert to find any trace of these. That is why we suggest that you use a free online scanner you can trust to run a malware scan on your computer. Of course, you can also use a reliable antimalware application that will not only detect all the threats present on your PC, but it will also eliminate them and protect your operating system from further attacks.

You need to be careful what software you download and where you download it from. Most users infect their machines when they end up on unfamiliar freeware sites or torrent sites. It is important to mention that there are malicious sites that can run a code in the background the moment your browser loads the page. This code can download and install malicious software onto your computer without your knowledge. But it is also possible that you simply click on corrupt third-party ads, either banner or pop-up ads, and that is how an infected bundle lands on your computer. Since you may not know or recall how this adware application showed up on your system, we recommend that you delete CoronaBorealis and perform a system scan right afterwards. Leaving any threats on board could further endanger your system security and your online activity.

This adware usually displays banner ads, pop-up ads, and coupons while you are using your browsers. However, these third-party ads may be dangerous to click on. You can never really know which one is legitimate and which one might take you to infected websites. CoronaBorealis does not use browser extensions to show ads; instead, it replaces a system file, dnsapi.dll, and that is how it can connect to remote adware servers to generate its advertisements. Clicking on an infected ad can be rather detrimental to you and your computer. You may simply infect your system with more malware programs, but you might also get scammed on fake websites. One of the most usual tricks schemers use is to make you click on their ad, which displays a warning about how you are unable to see some “important” content because of the lack of a driver or plug-in. Other misleading ads would tell you that your system has some errors that need immediate fixing, and the list goes on. These are very creative people, so you should never trust any of these disguised third-party ads, or else you may find yourself on a malicious website run by criminals. For example, landing on a fake online shop may cost you your personal and banking details if you are not careful enough. In order to avoid any of these horrible scenarios, you should remove CoronaBorealis right now.

It is not the simplest thing to make this adware disappear. But you can still do it even if you are not an experienced computer user, if you follow our instructions below. First, you have to uninstall the application via Control Panel. Although our researchers did not see CoronaBorealis changing the DNS settings apart from replacing the dnsapi.dll system file, we have included instructions for resetting your DNS settings as well, on a “just in case” bases. Finally, you have to restore this system file. Do not forget to keep all your programs and drivers updated because that is essential if you want to protect your computer and data from criminals trying to exploit the bugs in them.

Remove CoronaBorealis from Windows

Windows XP

  1. Tap Win+R and type in Control Panel. Click OK.
  2. Choose Add or Remove Programs.
  3. Select the application and press Remove.

Windows Vista and Windows 7

  1. Open the Start menu and go to Control Panel.
  2. Choose Uninstall a program.
  3. Click on the application and click Uninstall.

Windows 8, Windows 8.1, and Windows 10

  1. Press Win+Q and enter Uninstall a program.
  2. Select the application and press Uninstall.

Restore your DNS settings

Windows XP

  1. Click Start and go to Control Panel.
  2. Access Network Connections.
  3. Right-click on the active connection and choose Properties.
  4. Click Internet Protocol on the Local Area Connection Properties panel.
  5. Click Properties and pick Obtain DNS server address automatically.
  6. Press OK.

Windows Vista and Windows 7

  1. Press the Windows button on the Taskbar and open Control Panel.
  2. Pick Network and Internet.
  3. Open Network and Sharing Center.
  4. Click on your connection type.
  5. Click Properties and choose Internet Protocol Version 4 (TCP/IPv4).
  6. Click Properties and select Obtain DNS Server address automatically.
  7. Press OK.
  8. Press OK again.

Windows 8, Windows 8.1, and Windows 10

  1. Press Win+X and open Control Panel.
  2. Choose Network and Internet and open Network and Sharing Center.
  3. Click on the active connection next to Connections.
  4. Press Properties in the pop-up.
  5. Select Internet Protocol Version 4 (TCP/IPv4) in the item list box and click Properties.
  6. Mark the Obtain DNS server address automatically option and click OK.
  7. Press OK.

Restore dnsapi.dll

  1. Tap Win+R and enter cmd to open the command window. Click OK.
  2. Enter “sfc /scanfile=C:\Windows\system32\dnsapi.dll” and press the Enter key.
  3. If you have a 64-bit system, enter “sfc /scanfile=C:\Windows\syswow64\dnsapi.dll” and press the Enter key.
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