Keystroke interference software

Public computers are extremely susceptible to the installation of keystroke logging software and hardware, and this problem has been particularly prevalent in public libraries. Public computers are particularly susceptible to keyloggers because any number of people can gain access to the machine and in doing so install both a hardware keylogger and a software keylogger can be secretly installed in a matter of minutes.Anti keyloggers are often used on a daily basis to ensure that public computers are not infected with keyloggers, and are safe for public use.

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.

Countermeasures

The effectiveness of countermeasures varies, because keyloggers use a variety of techniques to capture data and the countermeasure needs to be effective against the particular data capture technique. For example, an on-screen keyboard will be effective against hardware keyloggers, transparency will defeat some screenloggers - but not all - and an anti-spyware application that can only disable hook-based keyloggers will be ineffective against kernel-based keyloggers.
Also, keylogger software authors may be able to update the code to adapt to countermeasures that may have proven to be effective against them.

On-screen keyboards

Most on screen keyboards (such as the onscreen keyboard that comes with Windows XP) send normal keyboard event messages to the external target program to type text. Every software keylogger can log these typed characters sent from one program to another.[18] Additionally, keylogging software can take screenshots of what is displayed on the screen (periodically, and/or upon each mouse click), which means that although certainly a useful security measure, an on-screen keyboard will not protect from all keyloggers.

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).
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).

Software-based keyloggers

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 on such as GetAsyncKeyState(), GetForegroundWindow(), etc. are used to poll the state of the keyboard or to subscribe to keyboard events.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.
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.
Packet analyzers: This involves capturing network traffic associated with HTTP POST events to retrieve unencrypted passwords.

Keystroke logging

Keystroke logging (often called keylogging) is the action of tracking (or logging) the keys struck on a keyboard, typically in a covert manner so that the person using the keyboard is unaware that their actions are being monitored. There are numerous keylogging methods, ranging from hardware and software-based approaches to electromagnetic and acoustic analysis.