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 ?
Apple is right to oppose demands that it install a back door on all devices.
pdf) signed a letter to President Barack Obama urging him to reject any proposals that would requireAaAaAeAeAaAeAeA decryption keys or back doors.
According to sources, many AI flights are operating with the back door shown as inoperative due to shortage of cabin crew.
Identifying and assessing back doors is only two-thirds of the process, however.
But if we were in the living room or kitchen and there was a fire at the front of the bungalows we would be unable to escape through the front and could not get out through the back because there are no back doors.
The black-and-white tape shows three masked men wearing oversize cotton shirts and baggy pants as they barrel through the back door around 8 p.
Part of this I speak of from personal experience: (A) I don't deal with death very well, as most people don't, and (B) in any nursing home that I've been in throughout my career, as well as most hospitals, you walk in through the front door, but you leave by the back door.
The neighbors came to the back door, bringing neighborhood news, cookies or a letter from the old country to share.
You may have installed a personal firewall or be inside a secured network, but this virus type opens back doors so that hackers can access your machine to steal data or use it as a zombie to attack other network PCs.
B,' propagates via mass e-mail and also through a worm component that leverages the back doors installed by the virus' predecessor, MyDoom.
Addressing to Kotli Satiyan Bar Association here on Wednesday, federal minister for Law Dr Babar Awan said that PPP did not come into power through back doors it was the people power that gave this party a chance to govern and we would come up to the expectations of the people adding that all avenues of those coming into power through back doors have been closed He said that despite passage of 63 years of freedom, Kotli Satiyan could not be freed adding that Kotly Satiyan would be provided all rights.
All transit buses should have an interlock system on their back doors that make the bus unable to move until they are completely shut, but front doors do not have the safety mechanism because they are in the driver's direct line of vision, said Eric Tate, the business representative for Teamsters Local 848, the union that represents York.