About anti-SoftICE tricks

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<TD><PRE>Method 01
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This method of detection of SoftICE (as well as the following one) is
9 `7 L% v2 r, w+ `4 B- [used by the majority of packers/encryptors found on Internet.
It seeks the signature of BoundsChecker in SoftICE
8 |& F+ W4 h" y2 Y3 V1 b& n  D! ]
    mov     ebp, 04243484Bh        ; 'BCHK'
    mov     ax, 04h
    int     3      
    cmp     al,4
9 T: ?- R, ?: _* e# }    jnz     SoftICE_Detected

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7 [4 w/ r! X7 k: G
Method 02
& B8 {& M7 N$ _" l7 U=========

Still a method very much used (perhaps the most frequent one).  It is used
to get SoftICE 'Back Door commands' which gives infos on Breakpoints,
or execute SoftICE commands...
It is also used to crash SoftICE and to force it to execute any commands
(HBOOT...) :-((  
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Here is a quick description:
6 J+ q" p" m7 N$ t-AX = 0910h   (Display string in SIce windows)
-AX = 0911h   (Execute SIce commands -command is displayed is ds:dx)
! B+ m7 O$ }4 p2 q; w2 ?! C-AX = 0912h   (Get breakpoint infos)
- h- N# ^+ G: j; z- f- C-AX = 0913h   (Set Sice breakpoints)
-AX = 0914h   (Remove SIce breakoints)
( J/ H4 W) ]- r
( P6 O1 g. k# H( s; _( NEach time you'll meet this trick, you'll see:
-SI = 4647h
; I, ?8 j- R0 `2 i/ Z-DI = 4A4Dh
Which are the 'magic values' used by SoftIce.
For more informations, see "Ralf Brown Interrupt list" chapter int 03h.
7 h, f* H& ~% w
Here is one example from the file "Haspinst.exe" which is the dongle HASP
9 ]% m: P0 I# s/ U" WEnvelope utility use to protect DOS applications:
% R+ r+ P2 ~2 T  S* H7 P. h

4C19:0095   MOV    AX,0911  ; execute command.
/ G2 ^2 b9 z( A$ e1 |4C19:0098   MOV    DX,[BX]  ; ds:dx point to the command (see below).
; D; S) f) P  M; c# A4C19:009A   MOV    SI,4647  ; 1st magic value.
4C19:009D   MOV    DI,4A4D  ; 2nd magic value.
4C19:00A0   INT    3        ; Int call.(if SIce is not loaded, jmp to 00AD*)
4C19:00A1   ADD    BX,02    ; BX+2 to point to next command to execute
9 K) X5 ~" O* L4C19:00A4   INC    CX
4C19:00A5   CMP    CX,06    ; Repeat 6 times  to execute
4C19:00A8   JB     0095     ; 6 different commands.
( d# y4 l$ `; [: S' B! c4C19:00AA   JMP    0002     ; Bad_Guy jmp back.
/ R3 T( K& d4 d4C19:00AD   MOV    BX,SP    ; Good_Guy go ahead :)

  o, ~: r/ Y4 D  T! C8 u# pThe program will execute 6 different SIce commands located at ds:dx, which
are: LDT, IDT, GDT, TSS, RS, and ...HBOOT.

' Y+ R9 G, d/ x4 r2 ^" F* the "jmp to 00ADh" is performed via an SEH if the debugger is not loaded.
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: E, O2 _( R6 n& X5 @Method 03
=========
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Less used method.  It seeks the ID of SoftICE VxD via the int 2Fh/1684h
$ Y2 p, i9 k5 S! I(API Get entry point)
6 f% j! @5 F& _8 M, |        
9 c& V1 d7 h! z( ~0 g
    xor     di,di
    mov     es,di
    mov     ax, 1684h      
    mov     bx, 0202h       ; VxD ID of winice
0 {& B$ O% t7 i2 C) d* m! a    int     2Fh
    mov     ax, es          ; ES:DI -&gt; VxD API entry point
9 i& ^1 R% k$ q3 a7 H) c    add     ax, di
( `( O% H$ |) W8 N& C    test    ax,ax
    jnz     SoftICE_Detected
( A; P" i; [" d' A5 j) B
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Method 04
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3 ]4 y$ U. |- ?. Q, Z/ ?
9 d. K2 ?$ M1 gMethod identical to the preceding one except that it seeks the ID of SoftICE
; C. n8 U$ e1 C. yGFX VxD.
' U$ M% Q8 D( F# ^6 s+ D
    xor     di,di
    mov     es,di
    mov     ax, 1684h      
    mov     bx, 7a5Fh       ; VxD ID of SIWVID
- F& D# h; u! z, E$ ^    int     2fh
& w) e" W6 b% y8 x: a$ s7 f( L" F    mov     ax, es          ; ES:DI -&gt; VxD API entry point
    add     ax, di
    test    ax,ax
    jnz     SoftICE_Detected
! m9 A# ?1 o1 R2 G1 {% ?: O" Q
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Method 05
=========
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' c2 }5 {" z+ g- |: m' O' RMethod seeking the 'magic number' 0F386h returned (in ax) by all system
debugger. It calls the int 41h, function 4Fh.
9 H! \- C! e) r3 ~6 GThere are several alternatives.  
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The following one is the simplest:

    mov     ax,4fh
    int     41h
    cmp     ax, 0F386
1 K+ |# d, m2 q6 k/ m& X5 `    jz      SoftICE_detected
- M* J1 M1 N/ |# k! b: Z
0 Q9 `8 u8 O. Y( F8 e
8 z% d9 |7 z6 A1 x6 ZNext method as well as the following one are 2 examples from Stone's
3 _1 S% q. V" H& o3 a2 q6 H"stn-wid.zip" (www.cracking.net):
+ G/ H; b6 P, k9 f
    mov     bx, cs
    lea     dx, int41handler2
    xchg    dx, es:[41h*4]
7 x9 K8 l/ F; d+ I2 v+ }9 k& H. O$ G    xchg    bx, es:[41h*4+2]
+ }: \% u0 V3 I! H4 p& E2 K    mov     ax,4fh
" M9 M6 h! a2 D; c; t+ @    int     41h
; v2 N  ~2 }1 P2 M% N6 t7 W    xchg    dx, es:[41h*4]
; v3 a# l5 Y% l* {& k' A. L    xchg    bx, es:[41h*4+2]
    cmp     ax, 0f386h
8 \, J* n5 W" A* T/ }7 R1 F    jz      SoftICE_detected

int41handler2 PROC
    iret
int41handler2 ENDP
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4 @! x3 ?# ~" C# s* L' v% Y
/ g; n' b& V. a5 b# E0 [. R7 XMethod 06
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2nd method similar to the preceding one but more difficult to detect:
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! a3 G; q) u0 C3 l, ?* l( lint41handler PROC
    mov     cl,al
* ]' Y! L  T0 V9 k* b' ~+ W    iret
int41handler ENDP

9 ?& _( ?& A! k' j5 P3 W
. Y- B0 ^: P6 B! d7 r) d) n9 h    xor     ax,ax
8 C# D% V8 E$ X    mov     es,ax
3 p  ^7 r3 V9 p0 ]9 X    mov     bx, cs
    lea     dx, int41handler
; L8 R! o. h0 s: ]8 R    xchg    dx, es:[41h*4]
; n9 y5 R* b% J& A    xchg    bx, es:[41h*4+2]
7 I2 ^% i3 e* A' S7 F6 H' _6 P    in      al, 40h
    xor     cx,cx
0 A$ @) Y9 S; p; O3 C4 J7 k    int     41h
: j* M3 y2 b% p: R) q2 B. [    xchg    dx, es:[41h*4]
    xchg    bx, es:[41h*4+2]
    cmp     cl,al
+ M+ S9 \1 a; d    jnz     SoftICE_detected
' @; U6 s1 A9 v% V/ p) S
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0 w. `+ M2 d: D- F- oMethod 07
=========
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Method of detection of the WinICE handler in the int68h (V86)
- `: P- X* J' |* y) Z
    mov     ah,43h
4 ^9 L6 K3 m' v% D( N    int     68h
    cmp     ax,0F386h
    jz      SoftICE_Detected


% M$ x  C) k/ w5 N- k=&gt; it is not possible to set a BPINT 68 with softice but you can hook a 32Bit
) K. p+ {! A- }' X& @   app like this:

, }/ z1 L" e3 @8 M! i& M   BPX exec_int if ax==68
0 v: B' g$ t2 `  J' I   (function called is located at byte ptr [ebp+1Dh] and client eip is
6 U. k' \# z' u; k0 o8 u   located at [ebp+48h] for 32Bit apps)
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5 |5 ^! g% D8 q" Z* ]Method 08
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  i5 L' i/ X; M. P# cIt is not a method of detection of SoftICE but a possibility to crash the
system by intercepting int 01h and int 03h and redirecting them to another
routine.
5 r! f/ j4 O" u4 {: ~) kIt calls int 21h functions 25h and 35h (set/get int vector) and ds:dx points
to the new routine to execute (hangs computer...)

& k. E& n9 |+ b/ V5 v* j+ N2 `    mov     ah, 25h
    mov     al, Int_Number (01h or 03h)
    mov     dx, offset New_Int_Routine
. z  t: X: q0 x0 C  e1 f7 a9 T    int     21h

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Method 09
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6 k5 w$ c+ A$ q; hThis method is closed to methods 03 and 04 (int 2Fh/1684h) but it is only
performed in ring0 (VxD or a ring3 app using the VxdCall).
The Get_DDB service is used to determine whether or not a VxD is installed
$ P. D" [7 d! O. {for the specified device and returns a Device Description Block (in ecx) for
that device if it is installed.

   mov     eax, Device_ID   ; 202h for SICE or 7a5Fh for SIWVID VxD ID
& Y& L% |* I. V) y   mov     edi, Device_Name ; only used if no VxD ID (useless in our case ;-)
% }& C; a4 c- ?, ]2 ~" d   VMMCall Get_DDB
2 d9 }9 h; ]% k- N* n- S   mov     [DDB], ecx       ; ecx=DDB or 0 if the VxD is not installed

Note as well that you can easily detect this method with SoftICE:
   bpx Get_DDB if ax==0202 || ax==7a5fh

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: x  z( k$ s1 s9 b- ZMethod 10
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  O) k8 e4 @- F2 R9 q=&gt;Disable or clear breakpoints before using this feature. DO NOT trace with
3 O8 u1 j4 y5 D% f9 h  SoftICE while the option is enable!!

This trick is very efficient:
by checking the Debug Registers, you can detect if SoftICE is loaded
(dr7=0x700 if you loaded the soft with SoftICE loader, 0x400 otherwise) or if
there are some memory breakpoints set (dr0 to dr3) simply by reading their
value (in ring0 only). Values can be manipulated and or changed as well
(clearing BPMs for instance)
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Method 11
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# N7 R" G7 E- s4 EThis method is most known as 'MeltICE' because it has been freely distributed
via www.winfiles.com. However it was first used by NuMega people to allow
3 o: r8 t) p$ k/ xSymbol Loader to check if SoftICE was active or not (the code is located
) X. s  v1 W: k) S* W) Linside nmtrans.dll).

The way it works is very simple:
: g# K0 l  I) l* {; ~It tries to open SoftICE drivers handles (SICE, SIWVID for Win9x, NTICE for
1 x: d& D- o! ~& p' G1 j4 F4 pWinNT) with the CreateFileA API.

' [. G& A. E2 }8 S; V- R) u5 FHere is a sample (checking for 'SICE'):
7 d6 W- Z+ K) W
  r/ j  S1 y! q- U' \BOOL IsSoftIce95Loaded()
1 {: }" e9 I& c, W8 }" g' a{
   HANDLE hFile;  
   hFile = CreateFile( "\\\\.\\SICE", GENERIC_READ | GENERIC_WRITE,
% r5 l6 }/ h; i" ~/ J                      FILE_SHARE_READ | FILE_SHARE_WRITE,
+ r8 ]4 F# r8 f                      NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
   if( hFile != INVALID_HANDLE_VALUE )
6 d8 H" n9 P. j9 @# a   {
      CloseHandle(hFile);
+ X$ [2 K: w- n* u; ]8 {      return TRUE;
   }
: N* P& d8 q8 g7 i   return FALSE;
( Y: A. r3 ^/ g" D% a}
0 [  H% m  e" A! z
Although this trick calls the CreateFileA function, don't even expect to be
! z3 p7 J/ V; i. f8 m: Wable to intercept it by installing a IFS hook: it will not work, no way!
In fact, after the call to CreateFileA it will get through VWIN32 0x001F
service _VWIN32_ReleaseWin32Mutex (via Kernel32!ORD_0001/VxDCall function)
and then browse the DDB list until it find the VxD and its DDB_Control_Proc
: R+ B7 |5 U9 @( [field.
, S9 l2 x  I: B9 [In fact, its purpose is not to load/unload VxDs but only to send a
% k3 @# Z% p" H$ v" z# k5 \W32_DEVICEIOCONTROL (0x23) control message (DIOC_OPEN and DIOC_CLOSEHANDLE)
* X3 k( [3 e( S7 _8 \2 Y7 w! Fto the VxD Control_Dispatch proc (how the hell a shareware soft could try
7 a. T1 S9 c+ }# B+ v& Y8 `/ lto load/unload a non-dynamically loadable driver such as SoftICE ;-).
9 U$ n) P2 s5 \! B4 P) @If the VxD is loaded, it will always clear eax and the Carry flag to allow
its handle to be opened and then, will be detected.
) _" C# f/ v6 l- q2 e% oYou can check that simply by hooking Winice.exe control proc entry point
while running MeltICE.
% v- B( Z, R9 I: ?

  00401067:  push      00402025    ; \\.\SICE
  0040106C:  call      CreateFileA
  00401071:  cmp       eax,-001
  00401074:  je        00401091


There could be hundreds of BPX you could use to detect this trick.
-The most classical one is:
  BPX CreateFileA if *(esp-&gt;4+4)=='SICE' || *(esp-&gt;4+4)=='SIWV' ||
    *(esp-&gt;4+4)=='NTIC'

1 R$ L0 {$ z1 S2 h' w; H: |+ x! A-The most exotic ones (could be very slooooow :-(
   BPINT 30 if eax==002A001F &amp;&amp; (*edi=='SICE' || *edi=='SIWV')  
! H8 T( k/ t! \. y5 d% I     ;will break 3 times :-(
/ _+ ^/ p) x' B
-or (a bit) faster:
   BPINT 30 if (*edi=='SICE' || *edi=='SIWV')
4 T" {. B- l1 [/ S2 }! r
   BPX KERNEL32!ORD_0001 if *edi=='SICE' || *edi=='SIWV'  
6 @) h- _' A% z     ;will break 3 times :-(

$ Q+ I; F" ?( T  [1 F- f$ W-Much faster:
   BPX VMM_GetDDBList if eax-&gt;3=='SICE' || eax-&gt;3=='SIWV'

Note also that some programs (like AZPR3.00) use de old 16-bit _lopen
3 M. q. J. I5 a0 Y! b: n! nfunction to do the same job:

   push    00                        ; OF_READ
   mov     eax,[00656634]            ; '\\.\SICE',0
  d- O) m( Z% l' c, `2 R1 y8 o0 c   push    eax
   call    KERNEL32!_lopen
   inc     eax
8 ]  S0 W2 I, |$ F/ l# n   jnz     00650589                  ; detected
. P9 ?8 q9 a' N4 O; n9 k   push    00                        ; OF_READ
! Z  J# q$ t( O/ R: Z3 k   mov     eax,[00656638]            ; '\\.\SICE'
; W+ v" {: R: D3 ~   push    eax
   call    KERNEL32!_lopen
9 B2 K* t1 x9 N: }   inc     eax
* \8 y4 M. y$ V' ]5 C4 v/ J7 J   jz      006505ae                  ; not detected
8 D( S& R! b& _' q
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1 E0 Z: J+ k% T# E8 Q' B* Z__________________________________________________________________________

$ g" y  g1 x, [& g, A+ v& E* n2 }Method 12
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! W' V1 `$ Q# {# V, |
- C9 D+ Y8 U2 `1 W+ s; FThis trick is similar to int41h/4fh Debugger installation check (code 05
% {" q8 W/ |$ x5 U. p&amp; 06) but very limited because it's only available for Win95/98 (not NT)
2 S" c/ L- P1 D6 mas it uses the VxDCall backdoor. This detection was found in Bleem Demo.
0 r, a! u: N0 c. n
   push  0000004fh         ; function 4fh
   push  002a002ah         ; high word specifies which VxD (VWIN32)
" [. N* p) y" H                           ; low word specifies which service
                             (VWIN32_Int41Dispatch)
- M4 k  c8 c% @9 e( a% W   call  Kernel32!ORD_001  ; VxdCall
   cmp   ax, 0f386h        ; magic number returned by system debuggers
   jz    SoftICE_detected
' Q  U0 p$ c! K- X+ o
: x: S1 f& n: S0 s  w' }Here again, several ways to detect it:

    BPINT 41 if ax==4f

- b' Y. f) M$ z9 V( g2 J    BPINT 30 if ax==0xF386   ; SoftICE must be loaded for this one

    BPX Exec_PM_Int if eax==41 &amp;&amp; edx-&gt;1c==4f &amp;&amp; edx-&gt;10==002A002A

    BPX Kernel32!ord_0001 if esp-&gt;4==002A002A &amp;&amp; esp-&gt;8==4f   ; slooooow!

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Method 13
=========

- q( K5 U+ K9 cNot a real method of detection, but a good way to know if SoftICE is
installed on a computer and to locate its installation directory.
It is used by few softs which access the following registry keys (usually #2) :
: O8 t; t8 d( {6 z1 ]' r! y& w
2 C( Q5 f, D- m1 h-#1: HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion
\Uninstall\SoftICE
, c( I1 m- M0 t9 _6 v-#2: HKEY_LOCAL_MACHINE\Software\NuMega\SoftICE
& b$ k: ^. ^1 b4 o3 ^7 t-#3: HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion
\App Paths\Loader32.Exe
6 }8 V1 h: h; J# O+ \
! n5 i# p$ l3 K: N4 `5 F; O
+ V2 q4 D3 x! I5 zNote that some nasty apps could then erase all files from SoftICE directory
# i) m% E; V4 k) _+ @(I faced that once :-(

0 W2 ?3 b* u: nUseful breakpoint to detect it:
3 }7 B% p) G0 [' \  m; f
     BPX _regopenkey if *(esp-&gt;8+0x13)=='tICE' || *(esp-&gt;8+0x37)=='tICE'
7 U( \: [+ Y. [
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Method 14
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+ w, Y8 y% q0 ]; J% A1 E/ p
) F, g/ P9 K9 [6 K0 RA call to VMM 'Test_Debug_Installed' service. As the name says, its purpose
is to determines whether a debugger is running on your system (ring0 only).

   VMMCall Test_Debug_Installed
- L9 u, }7 P. q  a- X' D0 O   je      not_installed

This service just checks a flag.
- s. o/ Z' m& Y0 F" e</PRE></TD></TR></TBODY></TABLE>