User-mode rootkits run in Ring 3, along with other applications as user, rather than low-level system processes.[27] They have a number of possible installation vectors to intercept and modify the standard behavior of application programming interfaces (APIs). Some inject a dynamically linked library (such as a .DLL file on Windows, or a .dylib file on Mac OS X) into other processes, and are thereby able to execute inside any target process to spoof it; others with sufficient privileges simply overwrite the memory of a target application. Injection mechanisms include:[27]
UEFI rootkit could infect a kernel of an iso inside an other iso
A rootkit can modify data structures in the Windows kernel using a method known as direct kernel object manipulation (DKOM).[33] This method can be used to hide processes. A kernel mode rootkit can also hook the System Service Descriptor Table (SSDT), or modify the gates between user mode and kernel mode, in order to cloak itself.[4] Similarly for the Linux operating system, a rootkit can modify the system call table to subvert kernel functionality.[34][35] It is common that a rootkit creates a hidden, encrypted filesystem in which it can hide other malware or original copies of files it has infected.[36] Operating systems are evolving to counter the threat of kernel-mode rootkits. For example, 64-bit editions of Microsoft Windows now implement mandatory signing of all kernel-level drivers in order to make it more difficult for untrusted code to execute with the highest privileges in a system.[37]
A kernel-mode rootkit variant called a bootkit can infect startup code like the Master Boot Record (MBR), Volume Boot Record (VBR), or boot sector, and in this way can be used to attack full disk encryption systems.[38]An example of such an attack on disk encryption is the "evil maid attack", in which an attacker installs a bootkit on an unattended computer. The envisioned scenario is a maid sneaking into the hotel room where the victims left their hardware.[39] The bootkit replaces the legitimate boot loader with one under their control. Typically the malware loader persists through the transition to protected mode when the kernel has loaded, and is thus able to subvert the kernel.[40][41][42] For example, the "Stoned Bootkit" subverts the system by using a compromised boot loader to intercept encryption keys and passwords.[43][self-published source?] In 2010, the Alureon rootkit has successfully subverted the requirement for 64-bit kernel-mode driver signing in Windows 7, by modifying the master boot record.[44] Although not malware in the sense of doing something the user doesn't want, certain "Vista Loader" or "Windows Loader" software work in a similar way by injecting an ACPI SLIC (System Licensed Internal Code) table in the RAM-cached version of the BIOS during boot, in order to defeat the Windows Vista and Windows 7 activation process.[citation needed] This vector of attack was rendered useless in the (non-server) versions of Windows 8, which use a unique, machine-specific key for each system, that can only be used by that one machine.[45] Many antivirus companies provide free utilities and programs to remove bootkits.
Once installed, a rootkit takes active measures to obscure its presence within the host system through subversion or evasion of standard operating system security tools and application programming interface (APIs) used for diagnosis, scanning, and monitoring.[60] Rootkits achieve this by modifying the behavior of core parts of an operating system through loading code into other processes, the installation or modification of drivers, or kernel modules. Obfuscation techniques include concealing running processes from system-monitoring mechanisms and hiding system files and other configuration data.[61] It is not uncommon for a rootkit to disable the event logging capacity of an operating system, in an attempt to hide evidence of an attack. Rootkits can, in theory, subvert any operating system activities.[62] The "perfect rootkit" can be thought of as similar to a "perfect crime": one that nobody realizes has taken place. Rootkits also take a number of measures to ensure their survival against detection and "cleaning" by antivirus software in addition to commonly installing into Ring 0 (kernel-mode), where they have complete access to a system. These include polymorphism (changing so their "signature" is hard to detect), stealth techniques, regeneration, disabling or turning off anti-malware software,[63] and not installing on virtual machines where it may be easier for researchers to discover and analyze them.
The fundamental problem with rootkit detection is that if the operating system has been subverted, particularly by a kernel-level rootkit, it cannot be trusted to find unauthorized modifications to itself or its components.[62] Actions such as requesting a list of running processes, or a list of files in a directory, cannot be trusted to behave as expected. In other words, rootkit detectors that work while running on infected systems are only effective against rootkits that have some defect in their camouflage, or that run with lower user-mode privileges than the detection software in the kernel.[29] As with computer viruses, the detection and elimination of rootkits is an ongoing struggle between both sides of this conflict.[62] Detection can take a number of different approaches, including looking for virus "signatures" (e.g. antivirus software), integrity checking (e.g. digital signatures), difference-based detection (comparison of expected vs. actual results), and behavioral detection (e.g. monitoring CPU usage or network traffic).
Rootkits are a sophisticated and dangerous type of malware. They run in kernel mode, using the same privileges as the OS. Because rootkits have the same rights as the OS and start before it, they can completely hide themselves and other applications. Often, rootkits are part of an entire suite of malware that can bypass local logins, record passwords and keystrokes, transfer private files, and capture cryptographic data.
Because Secure Boot has protected the bootloader and Trusted Boot has protected the Windows kernel, the next opportunity for malware to start is by infecting a non-Microsoft boot driver. Traditional anti-malware apps don't start until after the boot drivers have been loaded, giving a rootkit disguised as a driver the opportunity to work.
If a PC in your organization does become infected with a rootkit, you need to know about it. Enterprise anti-malware apps can report malware infections to the IT department, but that doesn't work with rootkits that hide their presence. In other words, you can't trust the client to tell you whether it's healthy.
Modern PCs with UEFI have a feature called Secure Boot which is designed to prevent the installation of unapproved or compromised operating systems which would infect your system with rootkits and other nefarious malware. Modern Linux distributions come with secure boot support enabled.
However, the first cyber threat that could be considered a rootkit emerged in 1999 by the name of NTRootkit. Since the most popular operating system for desktop computers at the time was Windows NT, NTRootkit specifically targeted Windows NT users. The program was developed by Greg Hoglund, who worked as a security researcher and launched NTRootkit as a proof-of-concept. NTRootkit gave way to He4Hook, which could hide malicious files and became known as a kernel rootkit. He4Hook made way for Hacker Defender, which could hide files and operating system registry keys. Later, in the early-2000s, another rootkit known as Vanquish contained the ability to hide files, registry keys and even complete directories.
Sometimes, hackers are looking to use a system as the origin of another attack. In such cases, hackers would use a rootkit to compromise a device and then use the compromised device to launch an attack on the target device. This gives hackers a lot of cover against possible detection. Moreover, once hackers have stealthily compromised several devices via rootkits and otherwise, the compromised devices could potentially become a part of a botnet to launch a DDoS attack.
Kernel mode rootkits modify the kernel of an operating system by either injecting new code into the kernel or replacing the existing code. Kernel mode rootkits use device drivers to push the altered code when infecting Windows devices. On the Linux platform, kernel mode rootkits exploit loadable kernel modules.
To remove kernel mode rootkits, users can try any reputable rootkit scanner. The best rootkit scanners are able to detect rootkits in the kernel. Removing the kernel rootkit is very difficult and requires advanced technical expertise. Generally speaking, the user will have to shut down the operating system infected with the kernel mode rootkit and then use another operating system to modify the infected file system.
The primary difference between Stuxnet and other rootkits at the time was that Stuxnet could cause real-world damage. Since Stuxnet could infect PLCs and other ICS, any industry that used modern automation techniques was at risk.
The difference between Flame and other normal rootkits was that Flame was extraordinarily modular. Hackers could add any number of modules to make the rootkit carry out different malicious activities. Flame created backdoors in the target devices and could also propagate independently via the present network.
The difference between Necurs and other rootkits is that Necurs can bring other malicious techniques to increase damage output. Hackers have used Necurs to spread ransomware to thousands of vulnerable machines. Necurs also spreads financial malware upon infecting a target device.
On the other hand, if you download a virus intentionally, for example, you were trying to get a copy of a game from a questionable resource, and you did this in Linux, but downloaded the file to your Windows partition, and you later ran the program in Windows, then you could indeed get infected at that point. The main point, however, is that Linux is impervious to Windows viruses, and Windows is impervious to Linux viruses. They simply do not speak the same language. 2ff7e9595c
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