About anti-SoftICE tricks

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<TD><PRE>Method 01
=========

This method of detection of SoftICE (as well as the following one) is
used by the majority of packers/encryptors found on Internet.
It seeks the signature of BoundsChecker in SoftICE

    mov     ebp, 04243484Bh        ; 'BCHK'
) W2 |0 G1 Q% U) \  w! f6 V1 Q    mov     ax, 04h
    int     3      
% _/ i- p- T' P/ a. y    cmp     al,4
" D4 U: c, a; m    jnz     SoftICE_Detected
2 o! ?- N& K( r# O) A: M
  K2 k% V# L0 }( @: ~4 C___________________________________________________________________________

Method 02
) ~. c7 T, M+ h6 w=========
8 o# t  K$ x5 {& C, v
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,
/ `3 |, E+ ~# y6 ^6 M1 h4 j9 R# Jor execute SoftICE commands...
It is also used to crash SoftICE and to force it to execute any commands
(HBOOT...) :-((  
# o0 K5 Y! G. p; c7 }
4 M3 k2 g6 z+ Z$ m  wHere is a quick description:
-AX = 0910h   (Display string in SIce windows)
-AX = 0911h   (Execute SIce commands -command is displayed is ds:dx)
-AX = 0912h   (Get breakpoint infos)
- h7 R' a& S0 D1 {% T% e  q" |2 _-AX = 0913h   (Set Sice breakpoints)
3 w! q* D5 r& E4 |( s4 h-AX = 0914h   (Remove SIce breakoints)
6 v' D5 l7 D+ {" Z" [- m
1 C4 d* H. y1 J8 s( C% PEach time you'll meet this trick, you'll see:
-SI = 4647h
-DI = 4A4Dh
/ @0 x# o, {' H/ hWhich are the 'magic values' used by SoftIce.
" S2 V5 B2 e3 x, V- aFor more informations, see "Ralf Brown Interrupt list" chapter int 03h.

Here is one example from the file "Haspinst.exe" which is the dongle HASP
Envelope utility use to protect DOS applications:

$ {; L/ H8 j# f$ ]3 T
1 n6 b3 e  b2 D* h8 n- l  M0 [4C19:0095   MOV    AX,0911  ; execute command.
7 h8 H( i# Z6 d' C4C19:0098   MOV    DX,[BX]  ; ds:dx point to the command (see below).
) ]6 J% ]% H$ G  u8 ^4C19:009A   MOV    SI,4647  ; 1st magic value.
4C19:009D   MOV    DI,4A4D  ; 2nd magic value.
' `; k6 j' K: Q8 P3 G4C19:00A0   INT    3        ; Int call.(if SIce is not loaded, jmp to 00AD*)
/ \5 }" [0 o  l! {6 R* L" V4C19:00A1   ADD    BX,02    ; BX+2 to point to next command to execute
5 a$ w. N  C3 D2 `4 h! v5 d4C19:00A4   INC    CX
4C19:00A5   CMP    CX,06    ; Repeat 6 times  to execute
  H  J# C8 e( c' j( {4C19:00A8   JB     0095     ; 6 different commands.
. n. `8 P) ~# _" T% i4C19:00AA   JMP    0002     ; Bad_Guy jmp back.
+ _* p) K" `' i4 C4C19:00AD   MOV    BX,SP    ; Good_Guy go ahead :)
! f5 N6 F' \  T
The program will execute 6 different SIce commands located at ds:dx, which
are: LDT, IDT, GDT, TSS, RS, and ...HBOOT.
5 o. E3 ?; h- M
* the "jmp to 00ADh" is performed via an SEH if the debugger is not loaded.
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8 d* K/ [7 b: I. \1 s' [

Method 03
/ l3 R! t. t% m: b=========

! B( f. W; @) W, l' xLess used method.  It seeks the ID of SoftICE VxD via the int 2Fh/1684h
' U7 W0 a! q, c) E1 r$ I(API Get entry point)
        

( M! K. N/ a8 ~8 M    xor     di,di
. |8 H" A3 F$ i/ |9 r$ a. r    mov     es,di
) L% x) [1 t6 [$ R( D0 Q    mov     ax, 1684h      
& c0 s) o( w/ j' {6 O+ ^! w6 u. V    mov     bx, 0202h       ; VxD ID of winice
    int     2Fh
    mov     ax, es          ; ES:DI -&gt; VxD API entry point
    add     ax, di
% V) Q. p6 h8 p# e0 H    test    ax,ax
    jnz     SoftICE_Detected

___________________________________________________________________________
+ H/ E) [# O7 d& b2 O* `
Method 04
=========
/ L  j/ |* t$ b2 U, p, k
Method identical to the preceding one except that it seeks the ID of SoftICE
GFX VxD.

    xor     di,di
2 o) q7 |4 J* e: v3 j1 d1 g  c    mov     es,di
    mov     ax, 1684h      
    mov     bx, 7a5Fh       ; VxD ID of SIWVID
, r8 a7 r: v" s. N9 V    int     2fh
' C: E5 y# W" P% m& |    mov     ax, es          ; ES:DI -&gt; VxD API entry point
    add     ax, di
7 o3 L$ S% Y' I    test    ax,ax
$ u7 o) b8 d+ ?" ]1 `, X0 p    jnz     SoftICE_Detected
7 r1 w) F5 k$ m! H
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5 N2 Q; I" H6 g2 A3 X9 D1 A
6 F9 x- B, d  q( {& c0 }# O6 lMethod 05
5 S2 i3 H7 h' l2 `% @0 ~=========

- W1 u9 b: r# K, O2 D, A- D  KMethod seeking the 'magic number' 0F386h returned (in ax) by all system
debugger. It calls the int 41h, function 4Fh.
There are several alternatives.  
  U, R0 w+ N% u; O
The following one is the simplest:
: B4 x' T7 v: z, a0 F$ H
    mov     ax,4fh
    int     41h
7 X* O* B% X* ]* L    cmp     ax, 0F386
    jz      SoftICE_detected
: b9 W5 w8 Q( P1 @* t! A$ y

% S& J1 @1 x! b2 P4 y( wNext method as well as the following one are 2 examples from Stone's
& R5 `! I8 R5 b8 W# ~3 y"stn-wid.zip" (www.cracking.net):
) Y& X+ @# U( _- x  {3 A
5 y, m6 x  n4 B- e) p$ v+ a7 |    mov     bx, cs
    lea     dx, int41handler2
1 ~! o+ S( s& [6 n! \4 T& O    xchg    dx, es:[41h*4]
    xchg    bx, es:[41h*4+2]
    mov     ax,4fh
    int     41h
    xchg    dx, es:[41h*4]
    xchg    bx, es:[41h*4+2]
    cmp     ax, 0f386h
    jz      SoftICE_detected

int41handler2 PROC
    iret
& F7 H% O" G6 F* _' U$ gint41handler2 ENDP
  d; f; z$ J4 ^( M7 \4 P5 Y" g' ~

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Method 06
=========
  L0 p% e/ t% I5 S! J) {
: k! S! X8 R3 D
2nd method similar to the preceding one but more difficult to detect:
  z- s" B% p. j  H* [. Q

. z0 h$ z8 _: C( mint41handler PROC
2 V% E0 W4 q) _8 _' _6 W4 E# |. c    mov     cl,al
" x+ I' ~2 [1 ?8 a    iret
int41handler ENDP
) R0 c2 p6 w0 Q  |
: h+ L1 F7 P  r4 z1 v8 ~
    xor     ax,ax
    mov     es,ax
3 Y+ x3 d' w1 t& j: }    mov     bx, cs
    lea     dx, int41handler
    xchg    dx, es:[41h*4]
1 V. `5 W! B, q& h* a    xchg    bx, es:[41h*4+2]
    in      al, 40h
    xor     cx,cx
    int     41h
. A; h: V0 |+ F& b  n    xchg    dx, es:[41h*4]
    xchg    bx, es:[41h*4+2]
    cmp     cl,al
9 I" i$ W6 w# x2 g' W' @5 I& A    jnz     SoftICE_detected
: n3 E/ }. G2 t* V4 q$ m: d2 E
2 P0 B# N( z6 Q$ g, ]8 {* Y: t_________________________________________________________________________
% M% J0 G- X9 e
$ C  G7 L1 Z1 o/ g7 u; x1 AMethod 07
& y5 l+ ?7 Q4 H; G2 x1 u=========

1 L. E* A' p( P3 V* L7 UMethod of detection of the WinICE handler in the int68h (V86)

    mov     ah,43h
    int     68h
    cmp     ax,0F386h
    jz      SoftICE_Detected


=&gt; it is not possible to set a BPINT 68 with softice but you can hook a 32Bit
   app like this:

' L8 A5 Q) O- l" }   BPX exec_int if ax==68
   (function called is located at byte ptr [ebp+1Dh] and client eip is
   located at [ebp+48h] for 32Bit apps)
4 _  s2 g8 T, _$ B& b8 n  ]__________________________________________________________________________
$ o) X8 F, A) H' |, m7 }

Method 08
=========
: w0 f8 P4 a/ i' Y0 f3 D2 q
It 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
4 k9 r% e! m2 Nroutine.
It calls int 21h functions 25h and 35h (set/get int vector) and ds:dx points
5 d' A7 Q1 `5 R# [+ L1 Qto the new routine to execute (hangs computer...)

    mov     ah, 25h
  j8 e8 q" t& p9 o    mov     al, Int_Number (01h or 03h)
7 h, ?, y: X7 O. b& \; O; _8 I    mov     dx, offset New_Int_Routine
1 v2 B- h% C3 _1 G, t    int     21h
- s6 W2 Q0 [6 V1 d1 L2 W* i
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) |% r2 n/ f, _( J* ]: C0 NMethod 09
0 F3 }" u! W# J=========

' w5 p$ N% z2 M4 KThis 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).
- e4 Y2 e5 p) \5 y# O1 pThe Get_DDB service is used to determine whether or not a VxD is installed
+ r2 a( d" v2 @for the specified device and returns a Device Description Block (in ecx) for
that device if it is installed.
# a7 P0 p% j0 F2 X. F3 N
6 z, ^6 o9 K& ?! W4 ^, M   mov     eax, Device_ID   ; 202h for SICE or 7a5Fh for SIWVID VxD ID
   mov     edi, Device_Name ; only used if no VxD ID (useless in our case ;-)
   VMMCall Get_DDB
3 f9 a8 g3 Z7 G! w# J. W$ ~1 \   mov     [DDB], ecx       ; ecx=DDB or 0 if the VxD is not installed
- f1 D2 D) W5 n& E" |. S$ z
. w  c4 j; |1 @Note as well that you can easily detect this method with SoftICE:
   bpx Get_DDB if ax==0202 || ax==7a5fh

; ?7 `$ H% I( t; o8 K__________________________________________________________________________

! v6 Q& C; n$ P! d( u( CMethod 10
( r+ W! g' v# [4 g) O=========

=&gt;Disable or clear breakpoints before using this feature. DO NOT trace with
  R0 B6 O- l! B& m7 C" y' L  SoftICE while the option is enable!!
% s1 Y8 O/ S! f" J4 q
This trick is very efficient:
7 y2 b" V2 k! d; O2 I* _; }by checking the Debug Registers, you can detect if SoftICE is loaded
9 I, {  g2 t8 w8 m(dr7=0x700 if you loaded the soft with SoftICE loader, 0x400 otherwise) or if
! J. ^& ~8 J  _  sthere are some memory breakpoints set (dr0 to dr3) simply by reading their
% O$ f* _0 ]# ]5 ]value (in ring0 only). Values can be manipulated and or changed as well
(clearing BPMs for instance)

& r8 U6 g+ c6 A. h# _+ p! x/ m__________________________________________________________________________
* g5 b" x2 C/ M. K
Method 11
# W) y' B4 @) M. o3 I# a4 A=========
! T$ I* c" c# @9 o0 e
This 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
Symbol Loader to check if SoftICE was active or not (the code is located
inside nmtrans.dll).
: S0 H; n$ x3 u8 p# T( b
. ]  r* }, ^' A$ h+ tThe way it works is very simple:
; ~/ ~7 h, C* K# `! m& \: ?It tries to open SoftICE drivers handles (SICE, SIWVID for Win9x, NTICE for
WinNT) with the CreateFileA API.
/ L/ N1 y4 M7 ^( ~& m
# n/ b% {! Z4 U% }+ Y) ?& KHere is a sample (checking for 'SICE'):
4 @* O8 ?& r- n$ }
& k8 d* R& e- O: c/ dBOOL IsSoftIce95Loaded()
2 c1 D& q5 P0 m& x{
   HANDLE hFile;  
" l- B5 \) r) x, F* N  U. J   hFile = CreateFile( "\\\\.\\SICE", GENERIC_READ | GENERIC_WRITE,
                      FILE_SHARE_READ | FILE_SHARE_WRITE,
                      NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
4 n  u% p% U9 w   if( hFile != INVALID_HANDLE_VALUE )
: k" \- U) o0 z+ o5 B2 E   {
      CloseHandle(hFile);
- U1 E: h1 j) K1 Z      return TRUE;
2 a( a( z2 o- o; t1 z   }
   return FALSE;
$ N" p4 ~- o/ W: o' Y}
2 n8 g8 \: U) J/ A7 B
Although this trick calls the CreateFileA function, don't even expect to be
7 Z5 Q" Q; J3 Dable to intercept it by installing a IFS hook: it will not work, no way!
1 S7 j3 i. g5 {" XIn fact, after the call to CreateFileA it will get through VWIN32 0x001F
9 |* |( e. P: w  kservice _VWIN32_ReleaseWin32Mutex (via Kernel32!ORD_0001/VxDCall function)
and then browse the DDB list until it find the VxD and its DDB_Control_Proc
field.
" V3 Q. W$ ^% \/ l* D- LIn fact, its purpose is not to load/unload VxDs but only to send a
W32_DEVICEIOCONTROL (0x23) control message (DIOC_OPEN and DIOC_CLOSEHANDLE)
9 N- m3 Y5 u8 x& _9 Hto the VxD Control_Dispatch proc (how the hell a shareware soft could try
to load/unload a non-dynamically loadable driver such as SoftICE ;-).
' S+ R7 o( e: C( w9 ZIf the VxD is loaded, it will always clear eax and the Carry flag to allow
5 V/ _+ r" O( i7 xits handle to be opened and then, will be detected.
You can check that simply by hooking Winice.exe control proc entry point
while running MeltICE.

1 g2 ~, G6 x7 ~2 h9 {
' @+ h* r# w+ t: a7 x  00401067:  push      00402025    ; \\.\SICE
  0040106C:  call      CreateFileA
, ]' W5 P: j5 d' Y, X  T" a+ ^9 ]  00401071:  cmp       eax,-001
1 Q! I7 x) l; S& s3 Y  00401074:  je        00401091
- l; V( ?* u$ C" @5 v5 p+ d, o2 x
- m& _+ V. \* S( C" Q1 ?% F6 o
There could be hundreds of BPX you could use to detect this trick.
' H! |  _+ \# G& N, N! E* t. r* s4 l-The most classical one is:
  BPX CreateFileA if *(esp-&gt;4+4)=='SICE' || *(esp-&gt;4+4)=='SIWV' ||
9 ?" U% k1 k& N- f2 I    *(esp-&gt;4+4)=='NTIC'
1 _4 F. c4 Y* P( K) |  j1 `
-The most exotic ones (could be very slooooow :-(
   BPINT 30 if eax==002A001F &amp;&amp; (*edi=='SICE' || *edi=='SIWV')  
     ;will break 3 times :-(

% F: ]. u+ T: B  n3 r6 L-or (a bit) faster:
   BPINT 30 if (*edi=='SICE' || *edi=='SIWV')
2 i- C+ B0 ?& b$ V. k; w. c+ `* E
   BPX KERNEL32!ORD_0001 if *edi=='SICE' || *edi=='SIWV'  
     ;will break 3 times :-(

-Much faster:
3 H3 S, Y) k# m   BPX VMM_GetDDBList if eax-&gt;3=='SICE' || eax-&gt;3=='SIWV'

6 Q+ I# ]  t5 V, F( g2 X# ^3 SNote also that some programs (like AZPR3.00) use de old 16-bit _lopen
function to do the same job:
; s7 ?; I1 Z3 B2 g3 R7 ]- ^8 I
: |- c/ n  o$ z7 Y   push    00                        ; OF_READ
+ [7 H$ Y. A/ C% {6 S   mov     eax,[00656634]            ; '\\.\SICE',0
) F5 W* l+ b3 c6 r   push    eax
   call    KERNEL32!_lopen
) A9 M$ n2 Z$ p   inc     eax
   jnz     00650589                  ; detected
; z+ L5 e, Z, z4 K9 H6 j% @+ z   push    00                        ; OF_READ
   mov     eax,[00656638]            ; '\\.\SICE'
   push    eax
   call    KERNEL32!_lopen
/ m* q7 |5 r) I, x& L: h   inc     eax
/ Z" B$ L5 v1 I4 g; ~   jz      006505ae                  ; not detected

( }1 Z* ^/ S. t
/ N* m: X6 |* G1 h% J0 Y" Z+ {. j__________________________________________________________________________

Method 12
; R- `1 R' g& z) G  _=========

This trick is similar to int41h/4fh Debugger installation check (code 05
&amp; 06) but very limited because it's only available for Win95/98 (not NT)
& n; p. i& B4 Z' jas it uses the VxDCall backdoor. This detection was found in Bleem Demo.
: k6 p5 X5 b7 N
   push  0000004fh         ; function 4fh
   push  002a002ah         ; high word specifies which VxD (VWIN32)
                           ; low word specifies which service
7 w; X& z; o% S; T                             (VWIN32_Int41Dispatch)
   call  Kernel32!ORD_001  ; VxdCall
   cmp   ax, 0f386h        ; magic number returned by system debuggers
   jz    SoftICE_detected

Here again, several ways to detect it:
+ A2 {, L1 s  }! U: c5 H
    BPINT 41 if ax==4f

, F  U' `% e1 U    BPINT 30 if ax==0xF386   ; SoftICE must be loaded for this one
2 Z7 w/ s4 F/ W; L7 H  c8 |
    BPX Exec_PM_Int if eax==41 &amp;&amp; edx-&gt;1c==4f &amp;&amp; edx-&gt;10==002A002A
' X. r# B7 [4 x& K
    BPX Kernel32!ord_0001 if esp-&gt;4==002A002A &amp;&amp; esp-&gt;8==4f   ; slooooow!
& W* h6 a8 S) E0 G: e
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Method 13
=========
: b9 E. ^# K) F1 b8 e
  s9 D: B: o1 R6 a/ E0 g$ ^Not a real method of detection, but a good way to know if SoftICE is
installed on a computer and to locate its installation directory.
5 J2 p( y8 {2 b+ NIt is used by few softs which access the following registry keys (usually #2) :
' U- l  I8 e, d9 s
* t' v. w' t, P: X6 f0 a-#1: HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion
\Uninstall\SoftICE
) b' T( r* e+ M: D8 L' d-#2: HKEY_LOCAL_MACHINE\Software\NuMega\SoftICE
-#3: HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion
\App Paths\Loader32.Exe


Note that some nasty apps could then erase all files from SoftICE directory
(I faced that once :-(

0 g- R' w+ m% w( J, sUseful breakpoint to detect it:

6 K: l* z2 r: D! V4 k: w; F     BPX _regopenkey if *(esp-&gt;8+0x13)=='tICE' || *(esp-&gt;8+0x37)=='tICE'
9 r, z9 Y) h7 [
__________________________________________________________________________
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0 ]4 {% M! s- H- Y6 r
Method 14
=========
8 z, C$ v' G: }7 H) c. J! D
A call to VMM 'Test_Debug_Installed' service. As the name says, its purpose
4 ^% B. ^' r7 E9 His to determines whether a debugger is running on your system (ring0 only).

8 Y; d5 Y4 Y% x   VMMCall Test_Debug_Installed
   je      not_installed

This service just checks a flag.
% |) j% w" F+ e* M2 L( l</PRE></TD></TR></TBODY></TABLE>