[jdmichal]

A rootkit is a different beast. A backdoor is simply a (covert) way to gain remote access to a system. A rootkit involves being able to elevate user permissions such that you have full control over the computer. Rootkits also typically use such permissions to hide themselves from normal user accounts.

I guess in a way you could see them as related, in that they both are access tools. A backdoor gets you remote access to the system in the first place. A rootkit gets you elevated access after you are in the system.

[commenter23]

No, that's wrong.

A rootkit is the thing you install once you have root - not a way to get root initially. It usually gives the attacker a means to access the machine in the future, even if the vulnerability she used is fixed in the future.

Rootkits are designed to hide themselves. They are essentially attacker installed backdooors.

A backdoor is basically a rootkit that is part of the original software as written by the original developer. The words have different connotations (rootkit is extremely negative, backdoors slightly less).

[mordocai]

No, that's wrong. Wikipedia has definitions that match my own knowledge, so i'll link and quote those.

https://en.wikipedia.org/wiki/Rootkit

"A rootkit is a collection of computer software, typically malicious, designed to enable access to a computer or areas of its software that would not otherwise be allowed (for example, to an unauthorized user) while at the same time masking its existence or the existence of other software."

https://en.wikipedia.org/wiki/Backdoor_(computing)

"A backdoor is a method, often secret, of bypassing normal authentication in a product, computer system, cryptosystem or algorithm etc. Backdoors are often used for securing unauthorized remote access to a computer, or obtaining access to plaintext in cryptographic systems.

A backdoor may take the form of a hidden part of a program,[1] a separate program (e.g. Back Orifice may subvert the system through a rootkit), or may be a hardware feature.[2] Although normally surreptitiously installed, in some cases backdoors are deliberate and widely known. These kinds of backdoors might have "legitimate" uses such as providing the manufacturer with a way to restore user passwords."

[woodman]

No, that is really wrong. Rootkits aren't for privilege escalation, see the paragraph immediately following your quote:

"... an attacker can install it once they've obtained root or Administrator access."

Calling BO a backdoor is a major corruption of the word, as you loose the only word for describing intentionally weakened security - so that you may describe a thing which already has several more explicitly defining names: malware, trojan, dropper, etc.

[jdmichal]

The installation of the rootkit is different from its purpose. A rootkit may require a root permission to install, perhaps piggybacking on another legitimate install such as in the famous Sony BMG rootkit. Or it may use an exploit to gain root access and install.

However, once installed, the purpose is the same: To provide the attacker with root permissions. It will also typically use its access to root permissions to hide itself from detection.

[woodman]

> A rootkit may require a root permission to install...

This sort of phrasing is misleading. If your OS restricts security sensitive kernel functions to the root user (hint: 99% of OSes do), then it isn't "may" - it is "must". Are there wrapper scripts that run privilege escalation exploits before installing the rootkit? Yes. Doesn't that make the exploit part of the rootkit? No, they are two very different things performing two different functions and are capable of operating independent of one-another.

> ...the purpose is the same: To provide the attacker with root permissions.

No, it is to allow code to run at the same privilege level as the kernel itself. Unrestricted loadable kernel modules. Think that is a distinction without a difference? OSX disagrees, as does Windows.

[jdmichal]

Regardless, the point of a rootkit is to provide an execution context with escalated privileges. Whether that means root user, kernel space, System user is I would think depends on the specific rootkit. (Whose name, of course, points to "root" privileges.) Which was my original definition and is inline with the posted definition from Wikipedia.

[codesterling]

There are too many "No, that's wrong"'s here for a bunch of people that aren't getting this quite correct. You do not need root access to install a rootkit, you simply need to exploit a security flaw that allows you to install, run, and avoid detection. This is easiest done by modifying the host to disable it's ability to even find you on the device. This is much more difficult on modern systems, so for most modern systems, they're installed as trojans using the privilege escalation of another application or install.

The connotation difference is the difference between getting hit with a 10mm and a 9mm. Negligible, as it's leaving a hole that you really don't want there.