Mobile code
Encyclopedia
In computer science
, mobile code is software transferred between systems, e.g. transferred across a network or via a USB flash drive
, and executed on a local system without explicit installation or execution by the recipient. Examples of mobile code include scripts (JavaScript
, VBScript
), Java applet
s, ActiveX controls, Flash animations, Shockwave movies (and Xtras), and macros embedded within Microsoft Office
documents.
Mobile code can also download and execute in the client workstation via email. Mobile code may download via an email attachment (e.g., macro in a Word file) or via an HTML email body (e.g., JavaScript). For example, the ILOVEYOU
, TRUELOVE, and AnnaK email viruses/worms all were implemented as mobile code (VBScript in a .vbs email attachment that executed in Windows Scripting Host).
In almost all situations, the user is not aware that mobile code is downloading and executing in their workstation.
Mobile code technologies can be used to support three different paradigms:
Mobile code can also be encapsulated or embedded in other file formats not traditionally associated with executable code. An example of this form of encapsulation is the presence of JavaScript
in a PDF.
Mobile code also refers to code "used for rent", a way of making software packages more affordable. i.e. to use on demand. This is specially relevant to the mobile devices being developed which are cellular phones, PDAs, etc. all in one. Instead of installing software packages, they can be "leased" and paid for on a per-usage basis.
Computer science
Computer science or computing science is the study of the theoretical foundations of information and computation and of practical techniques for their implementation and application in computer systems...
, mobile code is software transferred between systems, e.g. transferred across a network or via a USB flash drive
USB flash drive
A flash drive is a data storage device that consists of flash memory with an integrated Universal Serial Bus interface. flash drives are typically removable and rewritable, and physically much smaller than a floppy disk. Most weigh less than 30 g...
, and executed on a local system without explicit installation or execution by the recipient. Examples of mobile code include scripts (JavaScript
JavaScript
JavaScript is a prototype-based scripting language that is dynamic, weakly typed and has first-class functions. It is a multi-paradigm language, supporting object-oriented, imperative, and functional programming styles....
, VBScript
VBScript
VBScript is an Active Scripting language developed by Microsoft that is modeled on Visual Basic. It is designed as a “lightweight” language with a fast interpreter for use in a wide variety of Microsoft environments...
), Java applet
Java applet
A Java applet is an applet delivered to users in the form of Java bytecode. Java applets can run in a Web browser using a Java Virtual Machine , or in Sun's AppletViewer, a stand-alone tool for testing applets...
s, ActiveX controls, Flash animations, Shockwave movies (and Xtras), and macros embedded within Microsoft Office
Microsoft Office
Microsoft Office is a non-free commercial office suite of inter-related desktop applications, servers and services for the Microsoft Windows and Mac OS X operating systems, introduced by Microsoft in August 1, 1989. Initially a marketing term for a bundled set of applications, the first version of...
documents.
Mobile code can also download and execute in the client workstation via email. Mobile code may download via an email attachment (e.g., macro in a Word file) or via an HTML email body (e.g., JavaScript). For example, the ILOVEYOU
ILOVEYOU
ILOVEYOU, also known as Love Letter, is a computer worm that successfully attacked tens of millions of computers in 2000 when it was sent as an attachment to a user with the text "ILOVEYOU" in the subject line. The worm arrived e-mail on and after May 4, 2000 with the simple subject of "ILOVEYOU"...
, TRUELOVE, and AnnaK email viruses/worms all were implemented as mobile code (VBScript in a .vbs email attachment that executed in Windows Scripting Host).
In almost all situations, the user is not aware that mobile code is downloading and executing in their workstation.
Mobile code technologies can be used to support three different paradigms:
- Code on demandCode on demandIn distributed computing, code on demand is a general term for any technology that sends executable software programs from a server computer to a client computer upon request from the client's software ....
, - Remote evaluationRemote evaluationIn computer science, remote evaluation is a general term for any technology that involves the transmission of executable software programs from a client computer to a server computer for subsequent execution at the server...
, and - Mobile agentMobile agentIn computer science, a mobile agent is a composition of computer software and data which is able to migrate from one computer to another autonomously and continue its execution on the destination computer.-Definition and overview:...
s.
Mobile code can also be encapsulated or embedded in other file formats not traditionally associated with executable code. An example of this form of encapsulation is the presence of JavaScript
JavaScript
JavaScript is a prototype-based scripting language that is dynamic, weakly typed and has first-class functions. It is a multi-paradigm language, supporting object-oriented, imperative, and functional programming styles....
in a PDF.
Mobile code also refers to code "used for rent", a way of making software packages more affordable. i.e. to use on demand. This is specially relevant to the mobile devices being developed which are cellular phones, PDAs, etc. all in one. Instead of installing software packages, they can be "leased" and paid for on a per-usage basis.