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Also known as: Backdoor-CKA, Agent.MJ, Kivars

Category: Malware

Type: Backdoor trojan

Platform: Windows

Variants: Backdoor:Win32/Bifrose. Win32/Bifrose, Backdoor:Win32/Bifrose.EX

Damage potential: system performance issues, unauthorized access, data theft, installation of undesirable software, network connectivity problems, malware infection, file corruption and loss, stolen keystrokes, system performance issues, network connectivity problems, browser interference.


Bifrose is a prominent RAT (remote access trojan) first discovered in the 2000s. It was mainly active in Windows 95 through Windows 10, although since Microsoft started to implement better security features in its operating system, Bifrose hasn’t been as dangerous.

Bifrose can be used to create a network of compromised computers used in large-scale DDoS attacks.

Possible symptoms

RATs such as Bifrose can be difficult to detect because they often stay idle for a long time until they receive orders from the C2 center. Due to its communication with the attackers, you can recognize it from unusual spikes in traffic and unauthorized downloads.

Other Bifrose symptoms include:

  • Unauthorized downloads. You may notice unfamiliar apps in the start menu, task manager, or your desktop.
  • System performance issues. During a DDoS attack, your system may become virtually unusable, but smaller performance issues such as lags are common, too.
  • Strange system behavior. Bifrose may change your browser settings, install extensions, or alter the system in other ways.

Sources of the infection

Bifrose is spread via the internet and social media sites, or can be installed by other malware such as droppers, able to infiltrate a system and download more dangerous strains of malware. Bifrose also can be transferred via email attachments, pirated software, and exploit kits.


Bifrose may be posing as legitimate software, so only use official sources to update your software. Other ways to protect against Bifrose include:

  • Do not click on links and attachments if you haven’t requested them. Even if you`ve received a message from a person in your contacts, double check if they actually sent you anything.
  • Keep software up to date. Whether it’s your operating system or one of your security apps, make sure to update them as soon as possible.
  • Enable NordVPN’s Threat Protection Pro. It’s a NordVPN feature that scans files for malware before they’re downloaded to your device.


Windows Defender is likely to handle Bifrose without the need to download any third-party special software. So if you notice your system misbehaving, update your antivirus software and run a full system scan. If your antivirus does not find anything but you still suspect your device has been infected, try scanning your device with an anti-malware app.