I installed windows NT 4.0 service pack 6 on vmware player. Then I added Ollydbg 2 from vmware shared folder into windows NT. I extracted ollydbg zip and run ollydbg.exe. I am getting this error :

PSAPI.DLL is not found. This library contains important process and module oriented functions for OSes based on NT technology. Normal debugging is hardly possible. Do you want to continue ?

And then I am not able to debug program.

I can run same exe on my host windows 7 OS without any error. On windows NT, I can run Ollydbg 1.10. But when I try to debug file in Ollydbg 1.10, I am getting error "try to change eip or pass exception to program". After searching I found that I should install Ollydbg 2.

The reason I am using windows NT: I am debugging one malware and that only works on windows NT. But it is giving error "try to change eip or pass exception to program" as mentioned above.

  • Have you tried passing the exception to the program? Does the malware exit or continue as expected? – David Hoelzer Jul 15 '13 at 1:46
  • Yes even I tried to pass the exception in case of Ollydbg 1.10. But then my EIP points to address 00000000 and I keeps on getting same error "try to change eip or pass exception to program". Is there a problem with version of Ollydbg ? As I am using 1.10. I searched on this error and some suggested to use 2.0. But in case of 2.0 I am getting this dll error mention above – user1744108 Jul 15 '13 at 1:50
  • Have you tried using dynamic analysis tools without a debugger to be sure that the malware even works on Windows NT 4.0? If it runs correctly outside of OllyDbg but doesn't run correctly inside of OllyDbg, then it may very well be because of anti-debugging code in the malware, not an error in OllyDbg itself. – Jason Geffner Jul 15 '13 at 1:55
  • I think Bolzano virus can not run on windows NT version. I tried to execute executable malware file directly, but I was getting access violation exception. – user1744108 Jul 19 '13 at 6:13

I believe that a major part of your answer can be found here: http://www.ollydbg.de/download.htm

The relevant bit is:

The distribution includes files PSAPI.DLL and DBGHELP.DLL that are the Microsoft(R) Redistributable files. These files should be installed only in the directory where the Software resides. You should use supplied PSAPI.DLL only on Windows NT(R) 4.0. You are not allowed to distribute PSAPI.DLL or DBGHELP.DLL separately from the Software.

I would expect it to properly find PSAPI.DLL in the current directory where you are executing Olly. Verify that the file exists. If it does and it is still failing I would suggest copying it to C:\WINNT\SYSTEM and giving it another go.

It this does not resolve it consider sharing the name of the malware. It sounds pretty old so it can't be that secret! It may actually allow us to give you a more specific answer or even try it out ourselves to resolve it.

  • I found that my windows NT do not have psapi.dll neither in unzipped Ollydbg folder nor in SYSTEM folder. So I tried and copied dll from my host window 7 to windows NT (just a try) ollydbg and after that SYSTEM folder but it still don't work. So is there problem with my windows NT OS ? By the way, I am debugging polymorphic malware Bolzano. You can get its sample from oc.gtisc.gatech.edu:8080/search.cgi?search=bolzano – user1744108 Jul 15 '13 at 6:51
  • 1
    No. There's something wrong with the archive of Ollydebug that you have. PSAPI.dll should be in the zip file. I'd suggest that you download a fresh copy. – David Hoelzer Jul 15 '13 at 8:44
  • Ollydbg version 1 comes with psapi.dll. However, version 2 doesn't – PSS Jul 15 '13 at 12:44
  • I believe that he said that he is using Olly 1.10 which does come with the DLL. – David Hoelzer Jul 15 '13 at 12:45
  • I am using Olly 1.10 which has PSAPI.dll in its archive, but its not in case of Olly 2. As suggested by Jason, there are chances that virus is using anti debug technique and that why I am getting "try to change eip or pass exception to program" error in case of Olly 1.10. Or virus itself cannot run on windows NT. But I found one article on virus spth.virii.lu/29a4/29A-4.505.txt, and after looking at assembly code of virus I think it is running on windows NT. My goal is to get virus body (code which do actual infection) after it is decrypted. – user1744108 Jul 15 '13 at 14:34

I don't have NT4 vm
Also your link points to several samples
Providing exact MD5/SHA/some verifiable checksum of the sample can eliminate ambiguities while answering

here is a small walk through using basic hex editor and a basic disassembler of why it might be possible for that exception to be generated.

using winxp sp3 vm hxd hexeditor and ollydbg 1.10 in a basic dis-aaseembler mode

downloaded the first sample in openmalware

MD5:        f40547d521818f7c34754710f8603d5a
SHA1:       f9e3c0e824dda984046b4eedeef06f938805983b
SHA256:     a9beda469c835abbf416ea8da5462170eafdef215b96ac68523045600883855b
OCID:   245478739
Original Filename:  Virus.Win32.Bolzano.5572 

drag dropped to vpc 2007 xp sp3 vm

unzipped using given password infected

drag dropped into hxd hexeditor and verified checksums

MD-5:       F40547D521818F7C34754710F8603D5A
SHA-1:      F9E3C0E824DDA984046B4EEDEEF06F938805983B
SHA-256:    A9BEDA469C835ABBF416EA8DA5462170EAFDEF215B96AC68523045600883855B

all three checksums match ok

WORD MajorSubsystemVersion  
WORD MinorSubsystemVersion  
Contains the minimum subsystem version required to run the executable.   
A typical value for this field is 3.10 (meaning Windows NT 3.1).  


using ollydbg as a disassembler

view -> file -> malware.exe -> right click -> speacial -> pe header

ctrl+g 100

pe header shows

00000148    0300        DW 0003              ;  MajorSubsystemVersion = 3
0000014A    0A00        DW 000A              ;  MinorSubsystemVersion = A (10.)     

00000200    00100000    DD 00001000          ;  VirtualSize = 1000 (4096.)
00000204    00100000    DD 00001000          ;  VirtualAddress = 1000  <-----
00000208    00020000    DD 00000200          ;  SizeOfRawData = 200 (512.)
0000020C    00060000    DD 00000600          ;  PointerToRawData = 600    

00000228    00200000    DD 00002000          ;  VirtualSize = 2000 (8192.)
0000022C    00200000    DD 00002000          ;  VirtualAddress = 2000
00000230    00200000    DD 00002000          ;  SizeOfRawData = 2000 (8192.)
00000234    00080000    DD 00000800          ;  PointerToRawData = 800 <------

00000128    00100000    DD 00001000          ;  AddressOfEntryPoint = 1000

so we can start disassembling at 0x600

ctrl+g 600 right click -> disassemble


 1. 00000600    60              PUSHAD
 2. 00000601    E9 FA0F0000     JMP     00001600

virtual size of section is 1000 as we saw earlier
so it jumps to next section
next section starts at 0x800 as we saw earlier

ctrl+g 800 disassemble


00000800    E8 D50E0000     CALL    000016DA  (402eda) 400000 +2000 + (16da-800) 


000016DA    E8 00000000     CALL    000016DF  $+5 (402edf) 400000+ 2000+ (16df-800)  
000016DF    5D              POP     EBP  ebp  will be 402edf  
000016E0    81ED DF0E0000   SUB     EBP, 0EDF ebp will be 402000
000016E6    C3              RETN    will return to 805 or 402005

ctrl+g 805 disassemble

00000805    BF 000C0100     MOV     EDI, 10C00
0000080A    B9 00010000     MOV     ECX, 100
0000080F    33C0            XOR     EAX, EAX
00000811    F3:AE           REPE    SCAS BYTE PTR ES:[EDI]  
scan all bytes from 10c00 to 10d00 for 0  
00000813    75 0C           JNZ     SHORT 00000821          
if all not zero go to win95/98
00000815    BE 2D110000     MOV     ESI, 112D           win nt
0000081A    BF 0000F077     MOV     EDI, 77F00000       k32 base
0000081F    EB 0A           JMP     SHORT 0000082B
00000821    BE 25110000     MOV     ESI, 1125           win 95 / 98
00000826    BF 0000F7BF     MOV     EDI, BFF70000       k32 base

sets the base of kernel32.dll to edi for byte scanning puproses
looks if all 100 bytes starting at 10c00 are zero
if they are zero sets kernel base to 77f00000 (win nt k32 base no aslr fixed)
else to bff70000 (win 95 / 98 kernel32 base no aslr fixed)
esi to some offset

( esi = 1125 or 112d)  ( ebp = 402000)  40312d/25  1925 or 192d (800+1125 or 112d)                               
0000082B    03F5            ADD     ESI, EBP   
(so esi will be either 403125 or 40312d)
0000082D    89BD C8170000   MOV     DWORD PTR SS:[EBP+17C8], EDI 
saves the pointer kernel base guess why ?? 
00000833    BA 00000400     MOV     EDX, 40000
00000838    FC              CLD
00000839    B9 08000000     MOV     ECX, 8
0000083E    56              PUSH    ESI
0000083F    57              PUSH    EDI
00000840    F3:A6           REPE    CMPS BYTE PTR ES:[EDI], BYTE PTR>
00000842    5F              POP     EDI
00000843    5E              POP     ESI 

compares byte pattern in k32 dll

for 95/98 this pattern

00001925    C2 0400         RETN    4
00001928    57              PUSH    EDI
00001929    6A 22           PUSH    22
0000192B    2BD2            SUB     EDX, EDX

for win nt this pattern

0000192D    C2 0400         RETN    4
00001930    55              PUSH    EBP
00001931    8B4C24 0C       MOV     ECX, DWORD PTR SS:[ESP+C]

jumps to ok or not ok

00000844    74 0A           JE      SHORT 00000850  `right user with right os jump`
00000846    47              INC     EDI
00000847    4A              DEC     EDX
00000848    0F84 CD000000   JE      0000091B        `wrong user with wrong os jump`
0000084E  ^ EB E9           JMP     SHORT 00000839

if it finds the pattern will go to 850

else 91b

at 91b there is

0000091B    E8 BA0D0000     CALL    000016DA

so this will return to 920 (see above retn to 402005)

00000920    8B5424 20       MOV     EDX, DWORD PTR SS:[ESP+20]  
00000924    B9 40000000     MOV     ECX, 40
00000929    83EA 05         SUB     EDX, 5
0000092C    BE 4F180000     MOV     ESI, 184F

this will retn to kernel or exit thread address (pushad == 0x20)
all else are junk
exe contains nothing at 204f to 224f will simply exit via retn
(184f+800 ecx = 40 two lodsd = 80 dwords = 200 bytes = 224f)

if the region compared ok to retn value - 5 (see sub edx,5)
the app will crash and ollydbg can issue that warning

00000931    03F5            ADD     ESI, EBP 
00000933    AD              LODS    DWORD PTR DS:[ESI]
00000934    3BC2            CMP     EAX, EDX
00000936    AD              LODS    DWORD PTR DS:[ESI]
00000937    74 04           JE      SHORT 0000093D
00000939  ^ E2 F8           LOOPD   SHORT 00000933
0000093B    61              POPAD
0000093C    C3              RETN
0000093D    8985 47010000   MOV     DWORD PTR SS:[EBP+147], EAX
00000943    61              POPAD
00000944    EB 00           JMP     SHORT 00000946
00000946    68 00000000     PUSH    0 <---- apllication will crash 
0000094B    C3              RETN    eip not valid or 0

ollydbg will show dont know how to step because memory at address 0 is not readable try changing Eip or pass exception to program if it reaches here

disassembling at 850 or 402050

00000850    83C7 03         ADD     EDI, 3  add 3 to bytepattern address 
00000853    BE E70E0000     MOV     ESI, 0EE7  
00000858    03F5            ADD     ESI, EBP 402ee7 = 16e7 (ee7 -800 + 1000)
0000085A    8BC6            MOV     EAX, ESI
0000085C    83C0 07         ADD     EAX, 7  16e7+7 = 16ee

byte pattern at 16ee

000016EE  43 72 65 61 74 65 46 69 6C 65 4D 61 70 70 69 6E  CreateFileMappin
000016FE  67 41                                            gA

disassembling further

0000085F    50              PUSH    EAX   **pushes string CreateFileMapping**
00000860    8B85 C8170000   MOV     EAX, DWORD PTR SS:[EBP+17C**8] 
00000866    50              PUSH    EAX**  pushes kernel base 
00000867    FFD7            CALL    NEAR EDI  (can you guess ?? what api ??)

try walking ahead a bit :)

  • if you patch the kernel32 base address to suit xp kernel32 base @ EBP+17C8 (viz say 0x7c800000 instead of the hardcoded 77f00000 ) you can force the sample above to run in xp vm no need for NT (if you guessed you can tweak EDI to the correct address and infect xp also – blabb Jul 16 '13 at 9:37
  • i just noticed the article you mentioned in your comment it does not talk about the virus it contains complete source code for the virus. also if possible change the title of the question to something like how to debug bolzano virus using ollydbg 1.10 in nt vm or similar – blabb Jul 16 '13 at 9:44
  • I think Bolzano virus can not run on windows NT version. I tried to execute executable malware file directly, but I was getting access violation exception. – user1744108 Jul 19 '13 at 6:13
  • I am using sp 6 of windows NT 4.0. I found liutilities.com/malware/computer-virus/w32-bolzano article. It is mentioned here that "It also attacks Windows NT file system. However, if you have higher version of Windows NT like version 3.50 to 4.0 with service packs, you don’t have to worry about this virus’s attack". So is it because OS, I am getting the error ? – user1744108 Jul 19 '13 at 14:12
  • When I am debugging malware I am going to 'right OS with right user jump' because when I set break point at 00000850 83C7 03 ADD EDI, 3 ,debugger is coming to this step. But then when program comes to 00000867 FFD7 CALL NEAR EDI and api called is "FindNextFileA" I am getting EIP related error. – user1744108 Jul 22 '13 at 3:43

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