back door, backdoor(noun)

a secret or underhand means of access (to a place or a position)

"he got his job through the back door"

back door, backdoor(noun)

an undocumented way to get access to a computer system or the data it contains

back door, backdoor, back entrance(noun)

an entrance at the rear of a building

back door(Noun)

A subsidiary entrance to a building or house at its rear, normally away from the street.

back door(Noun)

A secret means of access to something.

back door(Noun)

The anus, generally used in reference to anal sex.

back door(Verb)

To attempt to accomplish by indirect means, especially when direct means are proscribed.

back door(Verb)

To enter a tube by accelerating from behind; to surf into an already formed hollow wave, in contrast to the normal method of slowing to allow a surfable wave to form.

back door(Adjective)

The path of a pitch which starts outside and then slides over the plate.

Back door(u)

a door in the back part of a building; hence, an indirect way

back door

[common] A hole in the security of a system deliberately left in place by designers or maintainers. The motivation for such holes is not always sinister; some operating systems, for example, come out of the box with privileged accounts intended for use by field service technicians or the vendor's maintenance programmers. Syn. trap door; may also be called a wormhole. See also iron box, cracker, worm, logic bomb.Historically, back doors have often lurked in systems longer than anyone expected or planned, and a few have become widely known. Ken Thompson's 1983 Turing Award lecture to the ACM admitted the existence of a back door in early Unix versions that may have qualified as the most fiendishly clever security hack of all time. In this scheme, the C compiler contained code that would recognize when the login command was being recompiled and insert some code recognizing a password chosen by Thompson, giving him entry to the system whether or not an account had been created for him.Normally such a back door could be removed by removing it from the source code for the compiler and recompiling the compiler. But to recompile the compiler, you have to use the compiler — so Thompson also arranged that the compiler would recognize when it was compiling a version of itself, and insert into the recompiled compiler the code to insert into the recompiled login the code to allow Thompson entry — and, of course, the code to recognize itself and do the whole thing again the next time around! And having done this once, he was then able to recompile the compiler from the original sources; the hack perpetuated itself invisibly, leaving the back door in place and active but with no trace in the sources.The Turing lecture that reported this truly moby hack was later published as “Reflections on Trusting Trust”, Communications of the ACM 27, 8 (August 1984), pp. 761--763 (text available at http://www.acm.org/classics/). Ken Thompson has since confirmed that this hack was implemented and that the Trojan Horse code did appear in the login binary of a Unix Support group machine. Ken says the crocked compiler was never distributed. Your editor has heard two separate reports that suggest that the crocked login did make it out of Bell Labs, notably to BBN, and that it enabled at least one late-night login across the network by someone using the login name “kt”.