Mobile code

In computer science, mobile code is software transferred between systems, e.g. transferred across a network, and executed on a local system without explicit installation by the recipient. Examples of mobile code include scripts (JavaScript, VBScript), Java applets, ActiveX controls, Flash animations, Shockwave movies (and Xtras), and macros embedded within Microsoft Office documents.^[1]

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:

• Code on demand,
• Remote evaluation, and
• Mobile agents.

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.^[2]

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.

See also

• Code mobility

References

1. ↑ Dr Lawrie Brown. "Mobile Code Security". Australian Defence Force Academy. Retrieved 23 April 2012. 
2. ↑ "Acrobat JavaScript Specification". Retrieved 18 November 2009.