You are probably familiar with computer viruses, adware, spyware, and other malicious programs, which are considered threats for the most part. However, a different form or class of malware (rootkits) might be the most dangerous of them of all. By “dangerous,” we mean the level of damage the malicious program can cause and the difficulty users have in finding and removing it.

What are rootkits?

Rootkits are a type of malware designed to grant unauthorized users access to computers (or certain applications on computers). Rootkits are programmed to remain hidden (out of sight) while they maintain privileged access. After a rootkit gets inside a computer, it easily masks its presence, and users are unlikely to notice it.

How does a rootkit harm a PC?

Essentially, through a rootkit, cybercriminals can control your computer. With such a powerful malicious program, they can force your PC to do anything. They can steal your passwords and other sensitive information, track all the activities or operations being executed on your computer, and even disable your security program.

Given rootkits’ impressive capabilities to hijack or put down security applications, they are quite difficult to detect or confront, even more so than the average malicious program. Rootkits can exist or operate on computers for a long period while evading detection and doing significant damage.

Sometimes, when advanced rootkits are at play, users are left with no choice but to delete everything on their computer and start all over again – if they want to get rid of the malicious programs.

Is every malware a rootkit?

No. If anything, only a small proportion of malware are rootkits. When compared to other malicious programs, rootkits are considerably advanced in terms of design and programming. Rootkits can do a lot more than the average malware.

If we are to go by strict technical definitions, then a rootkit is not exactly a form or type of malicious program. Rootkits simply correspond to the process used to deploy malware on a target (usually a specific computer or individual or organization). Understandably, since rootkits pop up quite often in the news about cyberattacks or hacks, the term has come to carry a negative connotation.

To be fair, rootkits run quite similarly to malware. They like to operate without restrictions on victims’ computers; they do not want protective utilities to recognize or find them; they usually try to steal stuff from the target computer. Ultimately, rootkits are threats. Therefore, they must be blocked (to stop them from coming in in the first place) or addressed (if they already found their way in).

Why are rootkits used or chosen?

Attackers employ rootkits for many purposes, but most times, they try to use them to improve or extend stealth capabilities in malware. With increased stealth, the malicious payloads deployed on a computer can remain undetected for longer while the bad programs work to exfiltrate or remove data from a network.

Rootkits are quite useful in that they provide a convenient way or platform through which unauthorized actors (hackers or even government officials) gain backdoor access to systems. Rootkits typically achieve the aim described here by subverting login mechanisms to force computers to give them secret login access for another individual.

Rootkits can also be deployed to compromise or overwhelm a computer to let the attacker gain control and use the device as a tool to perform certain tasks. For example, hackers target devices with rootkits and use them as bots for DDoS (Distributed Denial of Service) attacks. In such a scenario, if the source of the DDoS is ever detected and traced, it will lead to the compromised computer (the victim) instead of the real computer responsible (the attacker).

The compromised computers that participate in such attacks are commonly known as zombie computers. DDoS attacks are hardly the only bad stuff attackers do with compromised computers. Sometimes, hackers use their victims’ computers to carry out click fraud or to distribute spam.

Interestingly, there are scenarios where rootkits are deployed by administrators or regular individuals for good purposes, but examples of such are still quite rare. We have seen reports about some IT teams running rootkits in a honeypot to detect or recognize attacks. Well, this way, if they succeed with the tasks, they get to enhance their emulation techniques and security applications. They might also gain some knowledge, which they could then apply to improve anti-theft protection devices.

Nevertheless, if you ever have to deal with a rootkit, the chances are that the rootkit is being used against you (or your interests). Therefore, it is important that you learn how to detect malicious programs in that class and how to defend yourself (or your computer) against them.

Types of rootkits

There are different forms or types of rootkits. We can classify them based on their mode of infection and the level at which they operate on computers. Well, these are the most common rootkit types:

  1. Kernel-mode rootkit:

Kernel-mode rootkits are rootkits designed to insert malware into the kernel of operating systems to alter the OS functionality or setup. By “kernel,” we mean the central part of the operating system that controls or links operations between hardware and applications.

Attackers find it difficult to deploy kernel-mode rootkits because such rootkits tend to cause systems to crash if the code being used fails. However, if they do ever manage to succeed with the deployment, then the rootkits will be able to do incredible damage because kernels typically possess the highest privilege levels within a system. In other words, with successful kernel-mode rootkits, attackers get easy rides with their victims’ computers.

  1. User-mode rootkit:

The rootkits in this class are the ones that get executed by acting as ordinary or regular programs. They tend to operate in the same environment where applications run. For this reason, some security experts refer to them as application rootkits.

User-mode rootkits are relatively easier to deploy (than kernel-mode rootkits), but they are capable of less. They do less damage than kernel rootkits. Security applications, in theory, also find it easier to deal with user-mode rootkits (compared to other forms or classes of rootkits).

  1. Bootkit (boot rootkit):

Bootkits are rootkits that extend or improve upon the abilities of regular rootkits by infecting the Master Boot Record. Small programs that get activated during system startups constitute the Master Boot Record (which is sometimes abbreviated as MBR). A bootkit is basically a program that attacks the system and works to replace the normal bootloader with a hacked version. Such a rootkit gets activated even before a computer’s operating system starts up and settles down.

Given bootkits’ mode of infection, attackers can employ them in more persistent forms of attacks because they are configured to run when a system comes on (even after a defensive reset). Furthermore, they tend to remain active in system memory, which is a location rarely scanned by security applications or IT teams for threats.

  1. Memory rootkit:

A memory rootkit is a type of rootkit designed to hide inside a computer’s RAM (an acronym for Random Access Memory, which is the same thing as temporary memory). These rootkits (once inside the memory) then work to execute harmful operations in the background (without users knowing about them).

Fortunately, memory rootkits tend to have a short lifespan. They can only live in your computer’s RAM for a session. If you reboot your PC, then they will disappear – at least, in theory, they should. Nevertheless, in some scenarios, the restart process is not enough; users might end up having to do some work to get rid of memory rootkits.

  1. Hardware or firmware rootkit:

Hardware or firmware rootkits get their name from the place they are installed on computers.

These rootkits are known to take advantage of software embedded in the firmware on systems. Firmware refers to the special program class that provides control or instructions at a low level for specific hardware (or device). For example, your laptop has firmware (usually the BIOS) that was loaded into it by its manufacturer. Your router too has firmware.

Since firmware rootkits can exist on devices such as routers and drives, they can remain hidden for very long – because those hardware devices are rarely checked or inspected for code integrity (if they are even checked at all). If hackers infect your router or drive with a rootkit, then they will be able to intercept data flowing through the device.

How to stay safe from rootkits (tips for users)

Even the best security programs still struggle against rootkits, so you are better off doing whatever is necessary to prevent rootkits from entering your computer in the first place. It is not that difficult to stay safe.

If you keep to the best security practices, then the chances of your computer getting infected by a rootkit get reduced significantly. Here are some of them:

  1. Download and install all updates:

You simply cannot afford to ignore updates for anything. Yes, we understand that updates to applications can be annoying and updates to your operating system build can be disturbing, but you cannot do without them. Keeping your programs and OS updated ensures that you get patches to security holes or vulnerabilities that attackers take advantage of to inject rootkits into your computer. If the holes and vulnerabilities get closed, your PC will be better for it.

  1. Watch out for phishing emails:

Phishing emails are typically sent by scammers who are looking to trick you into providing them with your personal information or sensitive details (login details or passwords, for example). Nevertheless, some phishing emails encourage users to download and install some software (which is usually malicious or harmful).

Such emails might look like they have come from a legitimate sender or trusted individual, so you must watch out for them. Do not respond to them. Do not click on anything in them (links, attachments, and so on).

  1. Watch out for drive-by downloads and unintended installations:

Here, we want you to pay attention to the stuff that gets downloaded on your computer. You do not want to get malicious files or bad applications that install malicious programs. You must also be mindful of the apps that you install because some legitimate applications are bundled with other programs (which can be malicious).

Ideally, you should get only the official versions of programs from official pages or download centers, make the right choices during installations, and pay attention to the installation processes for all apps.

  1. Install a protective utility:

If a rootkit is to get inside your computer, then its entry is likely to be connected to the presence or existence of another malicious program on your computer. The chances are that a good antivirus or antimalware application will detect the original threat before a rootkit gets introduced or activated.

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How to detect rootkits (and some tips for organizations and IT admins)

There are few utilities that are capable of detecting and removing rootkits. Even the competent security applications (known to deal with such malicious programs) sometimes struggle or fail to do the job properly. Rootkit removal failures are more common when the malware exists and operates at the kernel level (kernel-mode rootkits).

Sometimes, the reinstallation of the OS on a machine is the only thing that can be done to get rid of a rootkit. If you are dealing with firmware rootkits, then you might end up having to replace some hardware parts inside the affected device or get specialized equipment.

One of the best rootkit detection processes requires users to execute top-level scans for rootkits. By “top-level scan,” we mean a scan that is operated by a separate clean system while the infected machine is powered down. In theory, such a scan should do enough to check for signatures left by attackers and should be able to identify or recognize some foul play on the network.

You can also use a memory dump analysis to detect rootkits, especially if you suspect that a bootkit – which latches onto the system memory to operate – is involved. If there is a rootkit in a regular computer’s network, then it probably will not be hidden if it is executing commands involving the use of memory –  and Managed Service Provider (MSP) will be able to view the instructions that the malicious program is sending out.

Behavior analysis is another reliable procedure or method that is sometimes used to detect or track rootkits. Here, instead of you checking for a rootkit directly by checking the system memory or observing attack signatures, you must look for rootkit symptoms on the computer. Things like slow operating speeds (considerably slower than normal), odd network traffic (which should not be there), and other common deviant patterns of behavior should give rootkits away.

Manager Service Providers can actually deploy the principle of least privileges (PoLP) as a special strategy in their customers’ systems to deal with or mitigate the effects of a rootkit infection. When PoLP is used, systems are configured to restrict every module on a network, which means individual modules gain access only to the information and resources that they need for their work (specific purposes).

Well, the proposed setup ensures tighter security between the arms of a network. It also does enough to block the installation of malicious software to network kernels by unauthorized users, which means it prevents rootkits from breaking in and causing trouble.

Fortunately, on average, rootkits are in decline (when compared to the volume of other malicious programs that have been proliferating over the past years) because developers are continuously improving the security in operating systems. Endpoint defenses are getting stronger, and a larger number of CPUs (or processors) are being designed to employ built-in kernel protection modes. Nevertheless, currently, rootkits still exist and they must be identified, terminated, and removed wherever they are found.