Keyboard Sniffer

[Gnosis]

The following is from "ROOTKITS, Subverting the Windows Kernel", by Greg Hoglund and James Butler:


Layering a driver requires some firsthand knowledge about how the Windows kernel handles drivers. This is best learned by example. In this chapter, we will walk you through creating a "hello layers" keyboard-sniffer rootkit. The keyboard sniffer will use a layered filter driver to intercept keystrokes.

The layered keyboard sniffer operates at a much higher level than that of the keyboard hardware. As it turns out, even working with hardware as simple as a keyboard controller can be very problematic.

With a layered driver, at the point at which we intercept keystrokes the hardware device drivers have already converted the keystorkes into I/O request packets (IRPs). These IRPs are passed up and down a "chain" of drivers. To intercept keystrokes, our rootkit simply needs to insert itself into this chain.

A driver adds itself to the chain of drivers by first creating a device, and then inserting the device into the group of devices. The distinction between device and driver is important.

Many devices can attach to the device chain for legitimate purposes. AS an example, a computer can have BestCrypt and PGP, both of which use filter drivers to intercept keystrokes and mouse activity.

To better understand how the device chain processes information, one must follow the IRP through its lifetime. First, a read request is made to read a keystroke. This causes an IRP to be constructed. This IRP travels down the device chain, with an ultimate destination of the 8042 controller. Each device in the chain, with an ultimate destination of the 8042 controller. Each device in the chain has a chance to modify or respond to the IRP. Once the 8042 driver has retrieved the keystroke from the keyboard buffer, the scancode is placed in the IRP and the IRP travels back up the chain. (A "scancode" is a number that corresponds to the key that was pressed on the keyboard.) On the IRP's way back up the chain, the drivers again have a chance to modify or respond to it.

 

[Gnosis]

Software-based keyloggers
A logfile from a software-based keylogger.

These are software programs designed to work on the target computer’s operating system. From a technical perspective there are five categories:

Hypervisor-based: The keylogger can theoretically reside in a malware hypervisor running underneath the operating system, which remains untouched. It effectively becomes a virtual machine. Blue Pill is a conceptual example.
Kernel-based: This method is difficult both to write and to combat. Such keyloggers reside at the kernel level and are thus difficult to detect, especially for user-mode applications. They are frequently implemented as rootkits that subvert the operating system kernel and gain unauthorized access to the hardware, making them very powerful. A keylogger using this method can act as a keyboard device driver for example, and thus gain access to any information typed on the keyboard as it goes to the operating system.
API-based: These keyloggers hook keyboard APIs; the operating system then notifies the keylogger each time a key is pressed and the keylogger simply records it. Windows APIs such as GetAsyncKeyState(), GetForegroundWindow(), etc. are used to poll the state of the keyboard or to subscribe to keyboard events.[1] These types of keyloggers are the easiest to write, but where constant polling of each key is required, they can cause a noticeable increase in CPU usage, and can also miss the occasional key. A more recent example simply polls the BIOS for pre-boot authentication PINs that have not been cleared from memory.[2]
Form grabbing based: Form grabbing-based keyloggers log web form submissions by recording the web browsing onsubmit event functions. This records form data before it is passed over the Internet and bypasses HTTPS encryption.
Memory injection based: Memory Injection (MitB)-based keyloggers alter memory tables associated with the browser and other system functions to perform their logging functions. By patching the memory tables or injecting directly into memory, this technique can be used by malware authors who are looking to bypass Windows UAC (User Account Control). The Zeus and Spyeye Trojans use this method exclusively.[citation needed]
Packet analyzers: This involves capturing network traffic associated with HTTP POST events to retrieve unencrypted passwords.

Remote access software keyloggers These are local software keyloggers with an added feature that allows access to the locally recorded data from a remote location. Remote communication may be achieved using one of these methods:

Data is uploaded to a website, database or an FTP server.
Data is periodically emailed to a pre-defined email address.
Data is wirelessly transmitted by means of an attached hardware system.
The software enables a remote login to the local machine from the Internet or the local network, for data logs stored on the target machine to be accessed.

Related features

Software keyloggers may be augmented with features that capture user information without relying on keyboard key presses as the sole input. Some of these features include:

Clipboard logging. Anything that has been copied to the clipboard can be captured by the program.
Screen logging. Screenshots are taken in order to capture graphics-based information. Applications with screen logging abilities may take screenshots of the whole screen, just one application or even just around the mouse cursor. They may take these screenshots periodically or in response to user behaviours (for example, when a user has clicked the mouse). A practical application used by some keyloggers with this screen logging ability is to take small screenshots around where a mouse has just clicked; these defeat web-based keyboards (for example, the web-based screen keyboards that are often used by banks) and any web-based on-screen keyboard without screenshot protection.
Programmatically capturing the text in a control. The Microsoft Windows API allows programs to request the text 'value' in some controls. This means that some passwords may be captured, even if they are hidden behind password masks (usually asterisks).[3]
The recording of every program/folder/window opened including a screenshot of each and every website visited, also including a screenshot of each.
The recording of search engines queries, instant messenger conversations, FTP downloads and other Internet-based activities (including the bandwidth used).


http://en.wikipedia.org/wiki/Keystroke_logging