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5 definitions found
 for back door
From The Collaborative International Dictionary of English v.0.48 :

  Back door \Back" door"\
     A door in the back part of a building; hence, an indirect
     way. --Atterbury.
     [1913 Webster]

From WordNet (r) 3.0 (2006) :

  back door
      n 1: a secret or underhand means of access (to a place or a
           position); "he got his job through the back door" [syn:
           back door, backdoor]
      2: an undocumented way to get access to a computer system or the
         data it contains [syn: back door, backdoor]
      3: an entrance at the rear of a building [syn: back door,
         backdoor, back entrance]

From Moby Thesaurus II by Grady Ward, 1.0 :

  105 Moby Thesaurus words for "back door":
     French door, afterpart, afterpiece, archway, back, back road,
     back seat, back side, back stairs, back street, back way,
     backstairs, barway, behind, bolt-hole, breech, bulkhead, by-lane,
     bypass, bypath, byroad, bystreet, byway, carriage entrance,
     cellar door, cellarway, clandestine, covert, covert way, detour,
     door, doorjamb, doorpost, doorway, escalier derobe, escape hatch,
     escape route, feline, front door, furtive, gate, gatepost, gateway,
     hatch, hatchway, heel, hidlings, hind end, hind part, hindhead,
     hole-and-corner, hugger-mugger, lintel, occiput, porch, portal,
     porte cochere, posterior, postern, privy, propylaeum, pylon, quiet,
     rear, rear end, rearward, reverse, roundabout way, scuttle,
     secret exit, secret passage, secret staircase, shifty, side door,
     side road, side street, skulking, slinking, slinky, sly, sneaking,
     sneaky, stealthy, stern, stile, storm door, surreptitious, tail,
     tail end, tailpiece, threshold, tollgate, trap, trap door,
     turnpike, turnstile, under-the-counter, under-the-table,
     undercover, underground, underground railroad, underground route,
     underhand, underhanded, unobtrusive
  
  

From The Jargon File (version 4.4.7, 29 Dec 2003) :

  back door
   n.
  
      [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?.
  

From The Free On-line Dictionary of Computing (18 March 2015) :

  back door
  wormhole
  
      (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].
  
     [{Jargon File]
  
     (1995-04-25)
  

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