back door

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back door

(security)
(Or "trap door", "wormhole"). 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. 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. The infamous RTM worm of late 1988, for example, used a back door in the BSD Unix "sendmail(8)" utility.

Ken Thompson's 1983 Turing Award lecture to the ACM revealed the existence of a back door in early Unix versions that may have qualified as the most fiendishly clever security hack of all time. The C compiler contained code that would recognise 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 *recognise 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 recognise 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 talk that revealed this truly moby hack was published as ["Reflections on Trusting Trust", "Communications of the ACM 27", 8 (August 1984), pp. 761--763].

back door

A secret way to take control of a computer. Also called "trap doors," back doors are built into software by the original programmer, who can gain access to the computer by entering a code locally or remotely. For example, a back door in an application would enable a person to activate either normal or hidden functions within the software. A back door in an operating system would provide access to all system functions in the computer. See Easter Egg and Back Orifice.
References in periodicals archive ?
While the market is looking at backdoors for the telecoms, note that the Villar group just 'backdoored' Bria Homes into Golden Haven.
While it appears OnePlus is responsible for leaving Engineer Mode on its devices, it is not directly responsible for the application itself or the backdoor it creates.
We are standing in solidarity with Apple and their decision to oppose the FBI's scheme to put backdoors to the iPhones," said Jeff Lyon, chief technical officer of the activist group Fight for the Future.
They have asked us to build a backdoor to the iPhone.
In the first half of 2015, the attackers used the following domains as command and control (C&C) servers for Backdoor.
Pakistani authorities asked for a backdoor to services like BES and BBM owing to the ongoing turbulence in the region.
The backdoor listing of NBS through Vulcan Industrial & Mining Corp.
She is also a writer, entrepreneur and owner of the new entertainment group Hollywood Backdoor, as well as a familiar face in the world of reality television.
ISLAMABAD, March 12, 2012 (Frontier Star): The PML-N and PPP have made contacts through backdoor channels in the wake of forthcoming elections' preparations, sources said.
A TRAIN firm has been accused of a 45 per cent ticket prices hike by the backdoor on services between Coventry and Birmingham New Street.
It was also asserted that (COAS )General Kayani advised president Zardari to commence backdoor diplomacy with India.