The Virus Lab – Fileless Malware

New forms of malware are constantly being developed, and keeping up with new strains can feel like a full-time job for quite a few people. Fileless malware has become the latest threat to gain traction in the realm of cybersecurity – but what exactly is fileless malware, and how can it affect your computer?

What is fileless malware?

Fileless malware is a type of malicious software that uses legitimate programs to infect your computer. Rather than infecting your computer with visible (and otherwise obvious) malicious programs, fileless attacks abuse tools built-in to the operating system to carry out attacks, leaving no trace and making it incredibly challenging to detect and remove. Essentially, the malware piggy-backs onto legitimate applications, running malicious code while your legitimate programs continue to performs their functions, effectively leaving you and your computer oblivious to what’s being done.

How does fileless malware work?

What makes fileless malware so effective in attacking your computer is that it’s already hiding in your system and doesn’t need to use malicious software as an entry point.

This stealthiness is what makes it so challenging to detect fileless malware and is inevitably what makes it so dangerous. By simply clicking on an ad or downloading a seemingly safe program, fileless malware runs malicious scripts alongside your existing Windows programs, making the malware seem safe and legitimate to any security programs.

Here are a list of ways fileless can infect your computer:

  • Through phishing emails, malicious downloads, and links that look legitimate: when you click on these links, they load to your PC’s memory, enabling hackers to remotely load codes via scripts that capture and share your confidential data.
  • Through applications you’ve already installed, like Microsoft Word or JavaScript: malicious code can be injected into already-installed, trusted applications, which can then be hijacked and executed.
  • Through local and highly trusted applications like Windows Management Instrumentation (WMI) and Microsoft PowerShell: fileless malware can target these legitimate programs remotely. For example, fileless malware can embed malicious scripts into legitimate PowerShell scripts – going along and injecting malicious code as it runs normal processes.
  • Legitimate-looking websites that actually are malicious: cybercriminals often create fake websites that are designed to appear like legitimate business pages or websites. When users visit these pages, the websites look for vulnerabilities in the Flash plugin, which allows malicious code to run in the browser memory.
An image of a computer with code across the screen to represent the fileless malware.

How to Prevent Fileless Malware from Infecting Your Computer

Fileless malware may be one of the more tricky types of malware to deal with, especially since it runs alongside legitimate apps – in many cases, the victim won’t even know that they’ve been infected! In order to prevent malware from infiltrating your computer, here are some steps you can take to protect yourself:

  • Being careful when downloading and installing applications – To actually infect your computer, malware needs to be downloaded first. Be sure that you’re only downloading files from secure and trusted websites.
  • Stay up to date with security patches and software applications – Updates exist for a reason. Security and software updates protect your computer from vulnerabilities that often are exploited by malware!
  • Watching out for phishing scamsPhishing scams have been on the rise lately, so keeping an eye out for them should be your top priority. Don’t open any emails or attachments from anyone you don’t know, and keep personal information private.

Because the malware runs parallel with your computer’s legitimate programs, it means that your operating system needs to be in use for the malware to run. Unfortunately, this means that the FixMeStick won’t be your best option for getting rid of fileless malware. The FixMeStick works by detecting malware before your computer is able to boot, but because fileless malware is only present while the computer is active, it means the FixMeStick can’t properly detect it.

The real key to counteracting these types of threats is understanding how the malware acts and the processes it undertakes as it attacks your computer. However, hunting down fileless malware by yourself can be a long and difficult task.

In this case, your best bet for combating fileless malware is to use a dependable antivirus such as McAfee Total Protection. With up-to-date blacklisting functions, the antivirus blocks unauthorized applications and code from running on servers and computers. It also automatically investigates abnormal behavior and searches for fileless attack footholds, making sure that your computer is completely virus-free.

Need extra protection on your computer? Click here to try McAfee Total Protection today!


Want to learn more about the different types of computer viruses? Check out other blogs in our Virus Lab series below!

What is Malware and Why Does it Exist?
What is Ransomware?
What is a Worm?
What is Adware?

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