Ŀ
 Presents
  ڿĴ VMag, Issue 3, 1 January 1999
  

                   䨪  ᮢ.
                                                           (c) .

   묨  ᠬ   뢠  ,   騥   ᢮   
ࠧ묨 ᯮᮡ (筮,  ᯮ騥 ࠧ   ஢)
  ६ ࠦ 䠩  ணࠬ.  筮,  ⠪  ᮤঠ
  樨  ஢騪   ஢騪.    ࠢ,  ᮧ
  ஬  ஢騪     ᮮ⢥騥    ஢騪,
⫨   㣠  ࠧ  ६.   ஢
  ᭮     易⥫쭮    ⢮  ணࠬ
ࠢ쭮 ஢ - ஢騪  ਯ (decryptor).
         ஢騪     ﭭ  -  
      ஢ 䠩.    ᮡ 
 ⥪஢ ஢ 䠩   ࠪ୮   
 ப (᪥  ᨣ).
     ।  ஢  ᭮  䨧.    뫨
।  Alan  Solomon,   Mechanism  of  Stealth,  Proceedings  Fifth
International Computer Virus and  Security Conference,  New York,  March
1992, pp. 232-238.

   ⪮  ஢.

   ஢ 1.    ᯮ ﭭ 祭   ࠧ  ᢮
஢騪.      ।    ﭭ
⪠   ஢騪.   ,  , 뢠  祭
묨  묨 (oligomorphic).
   :  Cheeba.A  (2 decryptors),  Cheeba.B  (2),  December_3rd (2),
Slovakia.2_00  (8),  Slovakia.2_02 (8),  Slovakia.3_0  (8),  V-Sign (6),
Whale (34).

   ஢ 2.   ஢騪    ﭭ         ᪮쪮
権.   Hਬ,   ᯮ   ࠧ   ॣ,   
ୠ⨢ 樨   ஢騪.      ⠪  
।  ᪥ - ⠭ ।   ਯ.
   : ABC, DM.330, Flip, Jerusalem.Moctezuma, Ontario.1024, PC-Flu,
Phoenix.1226,      Phoenix.2000,      Phoenix.Evil,     Phoenix.Phoenix,
Phoenix.Proud, Seat, Stasi, Suomi, Virus-101, VS.3900, VS.4000, ...

   ஢ 3.   ,   ᯮ騥    ஢騪   ,   
騥  ஢ ᭮ ,  -.  ⠪
,   NOP,  MOV AX,AX,  STI,  CLD,  CLI, ...   ⠪
  ⥪஢    ᪨,  ᫨  ந ᥨ 
 .
   :  Tequila,  StarShip,  V2Px.V2P1, V2Px.V2P1.Casper, V2Px.V2P2,
V2Px.V2P6, DrWhite, ...

   ஢ 4. ᯮ짮  ஢騪 塞 権 
६訢   権      ᮡ         ⬠
஢.   Hਬ,    MOV  AX,BX    塞
樨:  PUSH BX - POP AX; XCHG AX,BX; MOV CX,BX - MOV AX,CX; .... 
ਭ樯,   ⥪஢   ᮢ     ன
ॡࠥ ᪨.

   ஢ 5.  砥   ᥡ  ᯮ짮    ᫥ 
஢,    ⠪  ஢騪   ᯮ짮 ࠧ 
஢  ᭮  .        ᯮ짮,   
஢ ᭮  ᭮  ,  ஢   ᠬ  
ਯ    ᪮쪨 ஢騪,  । ஢뢠
  㣠,   ,   ।⢥,     .     ࠢ,
⥪஢ ᮢ  ஢  䨧    ᨣ
.   ⥪஢ , ᮡ, 祭 ⠪  -
祭 ᫮  ,   ,  쭮 த⥫쭠  ६
(difficult and  time-consuming  task).  ᫨    ⥪஢ ⠪
   쥧    ⮫쪮 ᠬ ஢騪,  
  祭 室 ந    ஢ ⥫
,   祭 ਣ쭮 ଠ樨   ࠦ 䠩.  
  ⨢ᮢ 祭 ᮢ ᫥ ஢ 䨧
ந -V  Dr. Web.  SMEG-,    ࠩ ,   
  .

    4  5 ஢:  MtE,  TPE,  APE,  DAME, DSME, DSCE, NED, MGEN,
CLME, SMEG-based, Uruguay, ...

       祭,    6  㯯  ᮢ.  
஢  ,   -      ,   騥     ணࠬ
-⥩,  ६訢  ⥫ .  ,
 㡨  ᢮ ணࠬ (⠫樨, ࠦ, ࠡ稪
뢠,      䠩      ..).         뢠
騬 (permutating).
           ᠬ    ⭮:     BadBoy,    BadBoy.Worthless,
CommanderBomber, Leech, SN.1444, ...

     ⮢  ᮮ饭 뫠  ᯮ짮   Vesselin
Bontchev 'Known Polymorphic Viruses',  Secure Computing January 1994 pp.
60-63.
