How to Avoid Fileless Malware

Sidestep the Silent Sniper: How to Avoid Fileless Malware

Not every piece of malware relies on an actual file on your system to execute programmed instructions. Fileless malware is an imminent threat that disrupts entire systems; a nasty exploit, it harnesses system-based anomalies to remotely infect your system, with little hope for detection. 

Studies estimate fileless and exploit-based malware will rise to a whopping 51% of all attacks in 2022 in enterprise environments. For the first time ever, this makes fileless malware as common as traditional file-based viruses.

Malware takes center stage when it comes to device security, especially in a world where internet-connected devices dominate every part of our work and lives. Attacks are also getting increasingly sophisticated, redefining what it means for an entity to be classified as “malware” in the first place. 

Let’s examine fileless malware in more detail and see what you can do to stay one step ahead.

Fileless Foes: Understanding Fileless Malware

A conventional virus will typically download a file-based agent (also known as a payload) on your system and use it to further its ulterior motives. Think of infected USB drives, infected apps and software, and viruses concealed in email attachments.

At the other end of the spectrum, a fileless virus doesn’t rely on any file, such as a download from the internet or an infected file on a USB drive, at all. It’s truly “fileless”, so to say; the attacker doesn’t need access to your system and can still take you in for a rather ghastly surprise through remote monitoring and ransomware. 

How does fileless malware work if it doesn’t employ a secret payload? Fileless malware uses native apps and built-in utilities already installed on your computer. That’s pretty much all it takes.

The virus simply exists in the RAM, your computer memory. It’s therefore memory-based, unlike traditional spyware, which lives on your computer’s physical storage. 

This is the reason fileless attacks so cleverly go unnoticed. When your trusted antivirus software scans files on the computer, it will detect trojans and worms but completely miss fileless malware, because there’s really “nothing” on the computer disk. 

a RAM chip with memory modules visible symbolizing how fileless malware lives in RAM
Fileless malware injects itself into your RAM leaving no footprint

Digital forensics teams have a hard time investigating the aftermath of a fileless malware attack too, which leaves no trail. One reboot and it vanishes into thin air, just like that, all thanks to RAM’s volatility. 

TL;DR: Is fileless malware deadly? You bet. It bites where it hits the most and then disappears leaving no signs.

A simple way for attackers to deploy fileless malware is to infiltrate your internet traffic and infect your device. Use a VPN to secure your internet traffic from network snoopers with unbreakable encryption. CyberGhost VPN offers a worry-free 45-day money-back guarantee.

Tracing Fileless Malware Origins

Fileless viruses might seem like the new kid on the block, but they’ve been with us for quite a few years now. Some experts believe they first appeared two decades ago. Code Red, one of the first fileless malware on record, took down entire enterprise networks, infecting even the White House web server.

Code Red used a vulnerability with an overflow in a Microsoft IIS web server buffer, the temporary data storage memory that stores data in transit. It swamped a web server with a long string of characters, which the server interpreted as a legitimate computer program. The result: hundreds of thousands of infected systems.

A computer screen showing how Code Red worm would throw an error message
The Code Red worm is a fileless malware that went ‘viral’ on web servers

Another well-known fileless malware attack was Operation Cobalt Kitty. The malware exploited PowerShell scripts to spy on a major Asian corporation for months on end. The attack compromised key management systems, file servers, and systems belonging to vice presidents and department directors at the company.

How does Fileless Malware Work?

At its core, a fileless virus uses legitimate system processes and user-downloaded apps to launch an attack. The attacker doesn’t need to download or copy anything onto your system — everything they need is already there in the operating system. It’s a multi-step process, where a fileless virus gains access to the system memory and then escalates its access privileges to work its way upwards.

Consider PowerShell, for example. It’s an amazing tool that administrators around the globe use every single day to automate tasks that would be otherwise tedious. Fileless malware attacks can use PowerShell scripts to execute commands and even load portable executable files directly from the memory without ever touching the disk.

Cybercriminals often use social engineering to trick their victim into clicking on a link that loads a code into the RAM custom-built to target an exploit. An attacker can even inject code into a Microsoft Word document and then use it to take control of your system. 

The key here is trust exploitation — fileless malware ruthlessly uses everyday tools we’ve come to trust against us. This makes it really difficult to combat them.

Concerned about social engineering attacks like phishing? Phishing is a highly successful form of cyber attack because it relies on malicious tricks that get you to mess up — and it’s human to make mistakes. Here are some tips you can follow to avoid becoming a phishing victim:

What can Fileless Malware do to Your System?

From a technical perspective, fileless malware can do anything a traditional virus can do. However, practical considerations make their design quite complex. Here are some of the main threat types you could face with fileless malware:

          • Vulnerability exploitation: The first step most fileless malware takes is to exploit a known or unknown vulnerability in an application. An attacker can craft a code that loads into your computer memory when you visit a website. The code can exploit a vulnerability in your browser to accomplish its objectives, like stealing your saved passwords or mining cryptocurrencies with your CPU resources (also known as cryptojacking).
          • Persistent surveillance: Fileless malware can stay active in the background, constantly monitoring system activities for months, exceeding the capabilities of modern keyloggers by leaps and bounds. Some viruses can even install a backdoor that remains operational for future surveillance.
          • Multi-phased attacks via payload installation: A rapidly evolving attack mechanism is when fileless malware discreetly ‘enters’ your system and then installs what is called a ‘payload’. This is a secondary, more conventional malware file, taking the attack to the next level once the fileless virus drops it to its destination.

We’ve barely scratched the surface here. As you can imagine, the possibilities with such sophisticated delivery mechanisms are endless.

How to Protect Yourself from Fileless Viruses

It’s exceedingly difficult to protect yourself from something that stealthily hides in your memory and leaves no footprint anywhere. If you want to stop fileless malware in its tracks, you need to embrace a proactive, multi-pronged approach. 

Prevent Attacks Before They Happen

Prevention is the best cure, goes the old adage. Nothing could be truer for fileless malware. The best defense is to prevent an attack from happening at all. It’s easier said than done but there are steps you can take to secure yourself from even the most obfuscated malware. 

Avoid clicking on links in unsolicited emails and stay aware of spear phishing attempts. Most fileless malware enters a system through a simple email link.

Only install apps and programs you absolutely trust. Never download files or apps from unofficial portals. Stick to the main system app stores and marketplaces for downloading apps.

Use a VPN

Your internet traffic is often exposed to your ISP and any cybercriminals on the network. Public Wi-Fi hotspots are, in particular, favorite haunts for threat actors. If an attacker can see your internet traffic, they can potentially execute a Man-in-The-Middle (MiTM) attack and plant fileless malware in your system. 

Use a VPN like CyberGhost VPN to encrypt your internet traffic and shield your browsing activity on all devices. CyberGhost VPN offers 7 simultaneous connections with just one subscription. What’s more, CyberGhost has advanced features like a Kill Switch and automatic Wi-Fi protection to keep you safe, even on unsecured networks. 
Download the CyberGhost VPN app on your devices and secure yourself from a plethora of cyberattacks.

Update, Update, Update

Keep your system up-to-date with the latest security patches and upgrades. It’s all too easy to lose track of OS updates. Further, regularly update each individual app or software program, be it a browser, word processor, or server software on all of your devices.

Fileless malware exploits vulnerabilities and software updates patch those as soon as they’re discovered, hopefully closing the door on the virus before it appears. Although zero-day attacks are still a potential problem.

Use Apps Vigilantly

Even when you use a highly trusted application such as Microsoft Word, be mindful of the documents you open and the macros you use and run. When not in use, turn off macros. You should also turn off PowerShell and Windows Management Instrumentation (WMI) when not in use.

Even seemingly simple macros can wreak havoc on your system. A macro embedded in a document can execute a malicious script, without you knowing.

A laptop with a spreadsheet open symbolizing how fileless malware can hide in macros
Macros can harbor fileless malware which are executed when run

Use Two-Factor Authentication

Build as many guardrails as possible when it comes to securing sensitive information. Wherever you have password protection, consider utilizing multi-factor authentication to add another security stop. The most popular varieties include getting a one-time PIN (OTP) or using biometrics like your fingerprint or face scan to unlock an app or account.

This way, even if your passwords are stolen in an attack, the malicious code will not be able to use those without additional authentication. 

Monitor Infection Signs

Lookout for noticeable signs of infection. Monitor the behavior of your device and observe any changes to the configuration you do not recall making. 

Consider examining your network data — if you’re a business, ask your IT teams to look out for signs of your device communicating with a remote server that was unintended. If you discover huge volumes of unexplained data leaving your device, that’s a red flag too.

Similarly, monitor your CPU, GPU, and memory usage when using your devices. If you find abnormally high usage levels when no process is running, it’s time to consider the possibility of a malicious actor at play.

Look out for error messages that pop up on your devices, especially random error messages that appear out of the blue.

Install Fileless Malware Detection Software

A tablet with the message "Warning Cyber Attack" flashing
Anti-malware software with behavioral analysis can detect fileless malware

Specialized antivirus software conducting AI-driven behavioral analysis can often detect fileless malware.

Look out for tools that offer centralized management of all devices so you can oversee all security statuses in one place rather than having to switch back and forth between multiple apps. The best anti-malware software has smart dashboards offering visibility into system and process status. These can significantly help to assess network communications, device statuses, and quickly isolate malware-infected systems should the need arise.

What to do When Your System is Infected with Fileless Malware

If you find yourself in a situation where fileless malware appears to have compromised a device, start by identifying all of the infection’s components.

Every system has a distinct attack surface — which refers to the number of unauthorized entry points to gain access into it. The greater the attack surface, the more entry points an attacker can use to gain control of the system.

If you think your device is infected, think about all the entry points into your system an attacker could use. Do you use a weak administrator password to log in? Are you running apps that haven’t been updated in a while? Was your password compromised in a data breach? 

Consider hiring a security specialist to conduct a detailed security audit to identify your systems’ attack surface. While this is recommended even before an attack occurs, it’s absolutely essential after one. 

An expert can also help you locate all individual malware pieces. If you simply try to get rid of the ‘visible’ portion of a fileless virus, there’s a good chance it will recapture your system in no time. It’s imperative to completely weed out all malware parts for complete security.

Sometimes, simply restarting your device will also rid you of some kinds of fileless malware, particularly those without persistence. Since they live in the system RAM, the moment you reboot the device, the RAM flushes all data, eliminating the malicious code in the process.

Security Information and Event Management (SIEM) tools can provide a bird’s eye view of all your devices and manage software, hardware, and network security in a holistic way. 

The fact that fileless malware conceals itself so efficiently means you’ll likely be better off seeking professional digital forensics services to remove fileless malware from your system.

Wrap Up

Fileless malware exists in your device’s memory and doesn’t leave a trace on the system’s hard disk, making it hard to find. These attacks typically harness the highly trusted apps and software already on your system, so there’s no reliance on you downloading any malicious files.

Malware attacks, including fileless malware, still need an entry point to gain access to your device. When you use a VPN to browse the web, you can secure your connection to the destination web server end-to-end. This lowers the risk of many cyber attacks, including fileless malware; a VPN also conceals your IP address from cybercriminals. 

Download CyberGhost VPN now to get an extra level of protection for your devices. One CyberGhost subscription supports up to 7 device connections simultaneously.

A proactive monitoring strategy is the best defense against fileless malware. Stay clear of phishing emails, watch out for suspicious behavior when using your devices, and use a multi-factor authentication approach to protect sensitive information.


How does fileless malware work?

Fileless malware works by gaining access to an entry point into your device. It can be as simple as an email or a document you receive from a colleague. The malware then injects itself into the system RAM and executes itself. As it leaves behind no trail on your system disk, fileless malware can be extremely difficult to detect.

How does fileless malware spread?

Unfortunately, fileless malware relies on the apps and software you already have installed on your system. It doesn’t require you to download any malicious files or programs. Fileless malware can exploit vulnerabilities in PowerShell scripts, .NET, WMI, and native OS apps and tools. Once the code executes in the system memory, it can then download additional ‘payload’ files.

If your internet traffic is exposed to an attacker, they can find ways to gain entry into your system and execute a fileless malware attack. Use CyberGhost VPN to encrypt your browsing sessions end-to-end, which forms a protective tunnel around your device’s connection. Outsiders won’t get past our unbreakable 256-bit AES encryption.

Is fileless malware really fileless?

Yes, ‘fileless’ malware is indeed fileless, as it doesn’t access your system disk and remains in your RAM. The malicious code exists in your system’s memory and is typically flushed out when the system is restarted. However, if it runs for long enough, fileless malware can become persistent and monitor your activities in the background for months.

Download the CyberGhost VPN app on your device to bolster your security online. You can connect up to 7 devices simultaneously with one CyberGhost connection which all benefit from features like automatic Wi-Fi protection, our Kill Switch, and Smart DNS protection.

Is it possible to remove fileless malware?

Yes, it is possible to remove fileless malware. That said, the task is challenging because a fileless malware attack is so difficult to detect. We recommend rebooting your system to remove early infections. Also use a smart anti-malware program that relies on behavioral analysis to monitor your system for suspicious activities.
The best response is still prevention, though. Use a premium VPN like CyberGhost to secure your internet connection so outsiders can’t inject fileless malware into your devices in the first place.

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