They may insert themselves into unused space within a binary so as not to change the size or other characteristics of those files (though they would affect a checksum).

CNN: Technology - Analysis: Understanding viruses

Now, Insert Coin semifinalist Radiator Labs is working to bring a solution to market that'll make your living space a lot more tolerable, and as an added bonus, it'll save energy at the same time.

ENGADGET

You may not notice the glossy facade at first, however, as the biggest hardware change in the new PS3 is where you insert disc-based media: a top-loading slider gets moved to the left, revealing a space for your brand new copy of Uncharted 3: Drake's Deception Game of the Year Edition (bundled with the 250GB console).

ENGADGET: PlayStation 3 Slim review (late 2012): is the third time a charm?