I'm comparing memory dumps in python with diStorm and volatility and try to analyze for given MemoryDumps (the 'dump' and the 'truth') whenever or not there was process injection.

Mainly I try to match processes and vads in to dumps to each other to compare them, but i get quiet a lot of white noise (false positives).

Here is a log I received comparing two clean memory dumps only by comparing modules (notepad and calc):

[10:08:13] Loading  'D:\notepad.zip'
[10:08:36] Loading  'D:\calc.zip'
[10:08:59] No match found for #208 "calc.exe"!
[10:08:59] 01/17    matching "csrss.exe"
[10:09:08] 02/17    matching "VBoxTray.exe"
[10:09:18] 03/17    matching "svchost.exe"
[10:12:51] 04/17    matching "ctfmon.exe"
[10:12:55] 05/17    matching "VBoxService.exe"
[10:13:24] 06/17    matching "smss.exe"
[10:13:25] 07/17    matching "explorer.exe"
[10:14:39] Module difference @ 0x772fb186   "\WINDOWS\system32\shlwapi.dll"
SUB AL, 0x77                    SUB AL, 0x77
POP ESP                         MOV DL, 0x14
DB 0x15                         DB 0xbd
DB 0x2d
[10:14:39] Module difference @ 0x772fb817   "\WINDOWS\system32\shlwapi.dll"
XOR [EAX], EAX                  XOR [EAX], EAX
ADD [EAX], AL                   DB 0x0
DB 0x0                          DB 0xbd
[10:14:39] Module difference @ 0x77fb5e17   "\WINDOWS\system32\ntdll.dll"
ADD [ECX+0x0], AH               ADD [EDI+0x0], CH
INS BYTE [ES:EDI], DX           DB 0x74
[10:14:39] Module difference @ 0x77fb5e1f   "\WINDOWS\system32\ntdll.dll"
ADD [EBP+0x0], AH               ADD [ECX+0x0], AH
DB 0x78                         DB 0x64
[10:14:39] Module difference @ 0x77fb5e27   "\WINDOWS\system32\ntdll.dll"
ADD [EAX], AL                   ADD [EAX+0x0], BH
DB 0x0                          DB 0x65
DB 0x73
[10:14:41] 08/17    matching "spoolsv.exe"
[10:15:24] 10/17    matching "svchost.exe"
[10:15:47] 11/17    matching "msmsgs.exe"
[10:16:06] 12/17    matching "svchost.exe"
[10:16:38] 13/17    matching "svchost.exe"
[10:17:08] 14/17    matching "winlogon.exe"
[10:18:03] 15/17    matching "services.exe"
[10:18:19] 16/17    matching "lsass.exe"
[10:19:15] Module difference @ 0x74414320   "\WINDOWS\system32\samsrv.dll"
ADD [EAX], AL                   JO 0x743bffb4
ADD [EAX], AL                   ADC AL, 0xc
ADD [EAX], AL                   OR AL, 0xde
ADD [EAX], AL                   INTO
[10:19:15] Module difference @ 0x74414546   "\WINDOWS\system32\samsrv.dll"
ADD [EAX], AL                   ADD [EAX], AL
ADD [EAX], AL                   DB 0xff
ADD [EAX], AL                   DB 0xff
DB 0x0                          DB 0xff
[10:19:16] Module difference @ 0x76f411bf   "\WINDOWS\system32\wldap32.dll"
ADD [EAX], AL                   ADD AL, CH
DB 0x3e                         JAE 0x76f2000f
DB 0xc
[10:19:17] Module difference @ 0x77cff169   "\WINDOWS\system32\rpcrt4.dll"
DB 0x3                          MOV AL, [0x49ff5965]
DB 0x35
DB 0xa1
IN AL, 0x3a
[10:19:20] 17/17    matching "System"

If i try ans also compare the executable image of the process I recieve even more noise

[12:10:13] 01/17    matching "csrss.exe"
[12:10:22] Instruction missmatch @ 0x5302db (13)
ADD [EAX-0x671ea561], CH        ADD AL, CH
RETF                            AND AL, 0x98
AND ECX, 0x2b0003               CWDE
[12:10:22] Instruction missmatch @ 0x53033b (6)
ADD [EBP+0x0], AH               ADD [EBX+0x0], DH
[12:10:22] Instruction missmatch @ 0x5304c7 (9)
ADD [EAX], AH                   ADD AL, CH
ADC EAX, 0x95d8bc65             ADD [EAX], AL
TEST AL, 0xe1                   ADD [EAX], AL
[12:10:22] Instruction missmatch @ 0x53065d (2)
ADD [EBX], AL                   ADD [EAX+EAX], AL
[12:10:22] Instruction missmatch @ 0x5307bb (6)
ADD [EBX+0x0], DH               ADD AL, CH
[12:10:22] Instruction missmatch @ 0x5307c5 (7)
ADD [EAX+EAX-0x439c6800], AH    ADD [ECX+0x0], BL
[12:10:22] Instruction missmatch @ 0x530864 (1)
STD                             FLD DWORD [EAX]
[12:10:22] Instruction missmatch @ 0x53086d (4)
ADD [EAX+EAX+0x18], AL          ADD [EDX+0x60551800], AL
[12:10:22] Instruction missmatch @ 0x53096c (13)
CMP [EBP+0x65], CH              MOV AL, [0x70e18a84]
MOV ESP, 0xe1a895d8             LOOPZ 0x530072
ADD EAX, 0xd0000300             ADD EAX, [EAX]

Each dump has been created on the same Windows XP VM. Any idea on how to filter that noise? Would be thankful for any hint and sorry for my bad english.


1 Answer 1


Unfortunately, certain factors are in play that will make it incredibly hard to filter. Specifically, everything from the calling convention windows uses to function prologs to space in said prologues to allow hot patching, etc...Windows' Application Binary Interface (ABI) is incorporated in every execution on the box. Naturally, this means you wont be able to filter it out, as several instructions are fairly common.

If you're merely trying to diff binaries to see how similar they are, the main one i would suggest is SSDEEP found in this answer

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