back door

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back door

(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 ?
But adding backdoors to encryption compromises the technology, and this has not gone unnoticed by the American public.
During the analysis, Kaspersky Lab researchers observed the attackers using the Epic malware to deploy a more sophisticated backdoor known as the "Cobra/Carbon system", also named "Pfinet" by some anti-virus products.
Blackwell's new show, tentatively titled Hollywood Bootcamp, is based on a set of strenuous performance workshops she offers through the newly formed Hollywood Backdoor group here in Los Angeles.
Another malicious program found during February also contained the Andromeda backdoor.
This amounts to a backdoor increase of 45 per cent for regular travellers between Birmingham and Coventry," said TSSA assistant general secretary Manuel Cortes.
In the name of PSUs, no more backdoor entry will be allowed.
dll contains a backdoor trojan that allows a remote user to access an infected computer and assume control with the security rights of the logged on users.
More than a third of people interviewed admitted that they still had backdoor access to their old employers' data and a quarter of those interviewed knew that former colleagues could access--and yet they did nothing about it
ADL downloads further malware, which BitDefender detected as Backdoor.
3 backdoors to the basket as 4 clears to the elbow.
SubSeven and BackOrifice are backdoor Trojan horses, which, as the piece does accurately describe, give an attacker the ability to spy on the target PC in real time.
Visitors can enter the Center for Simplified Strategic Planning Web site through this backdoor to go directly to the article, "The Strategy of Succession Planning," which teaches retiring executives about some advantages and possible pitfalls of succession planning.