Fileless Malware – Detection, Response and Prevention

Modern-day malware is much more menacing and vicious than ever before. They can evade early detection not just by traditional security tools but even advanced solutions like anti-malware, intrusion prevention systems, and intelligent email filters.

Therefore, they are being widely leveraged by attackers across the globe. One such menacing modern-day malware with a substantial increase in usage is fileless malware. As per data, fileless malware rates have grown by nearly 900%!  

Since it leaves no footprints, this modern malware is difficult to detect but not impossible. So, how do you detect and protect against fileless malware attacks? 

What is Fileless Malware?

Fileless malware is a malicious program/ code/ software that works directly within a system’s memory instead of the hard drive, leaving no footprints. 

Being a memory-based malware, code isn’t directly installed on the machine or stored in the machine. Instead, the malicious content goes straight to the memory without touching the hard drive. Owing to the lack of malicious files, fileless malware gets its name. 

Unlike traditional malware, it doesn’t require code to be installed on the target system. So, it is challenging to detect. Instead, this malware leverages native, legitimate, and otherwise benevolent tools and programs. Those are built into the system already to execute attacks and compromise systems. That is why fileless malware is known as living off the land or LOLbins. 

How Does a Fileless Malware Attack Work?

Though attackers don’t install code to launch fileless malware attacks, they will have to gain access to the environment to modify native tools to do their bidding. They use one or more of the following techniques to achieve this: 

• Social engineering and phishing attacks. Here users click a link or download a malicious attachment
• Exploit kits
• Fileless ransomware
• Stolen credentials
• Memory-only malware
• Hijacked native tools like JavaScript, Microsoft Word, and Microsoft PowerShell
• Registry resident malware

Once the fileless malware has infected the system, it makes lateral movement from one device to the next. The attacker gets remote access to the system. It enables them to steal credentials and create a backdoor to maintain persistence. 

Using the stolen credentials and the backdoor, they gain illegitimate access to data and systems. Thereby they can steal data and sabotage operations.

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Why is Fileless Malware so Dangerous?

• Being written directly to the RAM, fileless malware isn’t a rogue program or file. Additionally, it uses trusted, native tools, applications, and software to execute malicious activities. It escapes advanced tools like anti-malware software, sandboxing, and IPS systems, not just basic tools like anti-virus and firewalls.
• Even if the defenses detect and remove the original script, the malware remains operational using exploit kits like PowerSploit and CobaltStrike.

How to Detect Fileless Malware?

Don’t Use File and Signature-Based Detection

Traditional file-based and signature-based detection techniques are highly ineffective in fileless. These look for known signatures, check for static malicious/ rogue files and perform static testing of OS processes. So, they end up missing fileless malware.

You must leverage behavioral and pattern analysis, fingerprinting, and global threat feeds to detect this malicious malware effectively. In addition, use intelligent tools to automatically recalibrate the normal variance in malicious behavior and keep detecting malware even if it mutates. 

Look for Indicators of Attack

Instead of focusing on indicators of compromise which are challenging to detect, look for indicators of fileless malware attacks. For instance, lateral movements, code execution, data exfiltration, suspicious actions/ activities seemingly legitimate, and so on. 

Set triggers for such activities so your IT security team can scan the system and start fileless malware mitigation processes. 

Leverage Fully Managed Threat Hunting

Reputable and trusted security service providers like Indusface offer fully managed threat-hunting services to help you proactively and effectively identify fileless malware. 

They monitor the environment and detect malware in real-time using intelligent scanning, automated pen-testing, manual security testing, and false positive management. 

How to Prevent Fileless Malware Attacks?

Detection of such malware doesn’t automatically prevent such fileless attacks. For fileless attack protection, you must identify vulnerabilities, flaws, and gaps that malicious attackers could exploit to do their bidding and secure them proactively. 

You can prevent these attacks by combining fileless malware detection with next-gen, fully managed security solutions. Such a solution must be comprehensive and provide multiple layers of security. 

Other measures include: 

• Patching and updating everything in the environment
• Continuous logging and monitoring
• Hardening the security posture proactively
• Continuously educating employees and users to ensure they don’t fall prey to phishing and other scams

The Way Forward

Fileless malware may be stealthy, evading traditional security measures. However, with the right security measures and solutions, you can effectively detect and prevent them.

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