Didier Stevens

Thursday 11 May 2017

Crack A ZIP Password, And Fly To Dubai …

Filed under: My Software,Update — Didier Stevens @ 0:00

We had to crack a password protected ZIP file, to discover that just few hours later, we would fly to Dubai for our NVISO team building event.

This inspired me to update my zipdump.py tool. This tool can handle password protected ZIP files. Using default password “infected”, or a password that can be provided with option -p.

In this new version, you can provide a list of password in a text file using option -P. Turns out that this simple dictionary attack just using Python is surprisingly quick (at least to me): 8000 passwords per second on an average machine.

 

 

zipdump_v0_0_6.zip (https)
MD5: B605DEABFC5458488B6487B1E9104085
SHA256: DDC2CE94D250CBDE62AD1EBE650654E4A50C51F97CADF412B16A553242819772

Monday 10 April 2017

Update: re-search.py Version 0.0.4

Filed under: My Software,Update — Didier Stevens @ 0:00

This version has one new option: -G or –grepall.

re-search_V0_0_4.zip (https)
MD5: 965C484CC5BF447B390BA4E176698972
SHA256: D2F3A52F7590CD38E796B6F6209FC87A1BD6451F1787010557FA39E25AFDBC2F

Tuesday 7 March 2017

Update: oledump.py Version 0.0.27

Filed under: My Software,Update — Didier Stevens @ 0:00

This new version of oledump.py adds some extra features for YARA rule scanning.

oledump.py declares 2 external variables that can be used in your YARA rules.

External variable streamname is a string with the stream name, as printed in oledump’s report.

External variable VBA is a boolean that is set to true when the data to scan is VBA source code. Previous versions of oledump would scan the raw stream content with YARA, but this new version also decompresses all streams with VBA macros, and concatenates them together to scan them after all streams have been scanned.

Example of a rule using external variable VBA:

rule VBA_Autorun
{
    strings:
        $a = "AutoExec" nocase fullword
        $b = "AutoOpen" nocase fullword
        $c = "DocumentOpen" nocase fullword
        $d = "AutoExit" nocase fullword
        $e = "AutoClose" nocase fullword
        $f = "Document_Close" nocase fullword
        $g = "DocumentBeforeClose" nocase fullword
        $h = "Document_Open" nocase fullword
        $i = "Document_BeforeClose" nocase fullword
        $j = "Auto_Open" nocase fullword
        $k = "Workbook_Open" nocase fullword
        $l = "Workbook_Activate" nocase fullword
        $m = "Auto_Close" nocase fullword
        $n = "Workbook_Close" nocase fullword
    condition:
        VBA and any of ($*)
}

The condition of this rule is true when external variable VBA is true and when at least one of the strings are found:

20170306-184258

This rule is included in a new set of YARA rules I included with oledump.py: vba.yara.

I made a video to illustrate this:

And there is also a new plugin: plugin_str_sub. It tries to de-obfuscate strings with padded characters:

oledump_V0_0_27.zip (https)
MD5: A6C6728E20AE46A4FECC5F3976AF33BF
SHA256: 54FE550D5102A0E9428F6BD9B5170B50797EDA2076601634519CDBB574004A3C

Monday 6 March 2017

Update: cut-bytes.py Version 0.0.5

Filed under: My Software,Update — Didier Stevens @ 0:00

I just updated the manual of this version, to explain here documents.

cut-bytes_V0_0_5.zip (https)
MD5: B20B9758D50C846CD0E0AEB9E0B15101
SHA256: B12D1E1C510ED4CC820C5D2F62897DF71E567B0D3B23AC36653236D30104157F

Sunday 5 March 2017

Update: re-search.py Version 0.0.3

Filed under: My Software,Update — Didier Stevens @ 0:00

A very small update to re-search.py: I added a regular expression for strings to the library:

20170303-224430

re-search_V0_0_3.zip (https)
MD5: 6C4F59C4BA5DAC1D16D3E09D1E333FD0
SHA256: BFB019F1350F7D63FB3704322F62894A4B17D8EE03CC186156F2A97045E47F58

Sunday 26 February 2017

Update: translate.py Version 2.4.0

Filed under: My Software,Update — Didier Stevens @ 9:19

I added a feature similar to “here files” to translate.py. It’s something I already did in xor-kpa.py.

In stead of using an input filename, the content can also be passed in the argument. To achieve this, precede the text with character #.
If the text to pass via the argument contains control characters or non-printable characters, hexadecimal (#h#) or base64 (#b#) can be used.

Example:
translate.py #h#89B5B4AEFDB4AEFDBCFDAEB8BEAFB8A9FC “byte ^0xDD”
Output:
This is a secret!

translate_v2_4_0.zip (https)
MD5: B33830C68D8A8A7534AF178243658E70
SHA256: A01AB10FCE42664869C4E31DB1AB2E1E0237172D0AE9685549A09BF866D7F885

Saturday 25 February 2017

Update: rtfdump.py Version 0.0.5

Filed under: My Software,Update — Didier Stevens @ 10:28

This new version of rtfdump.py adds object extraction (-E) and can also handle objects obfuscated with \dde0000…

20170225-112653

rtfdump_V0_0_5.zip (https)
MD5: 14475C70D992FB72306D5F83815DDE19
SHA256: A26A60536509BA7CF55FF1876E8BC3A6DBA43F1EF8841F159D55411FD11B5078

Wednesday 22 February 2017

Update: base64dump.py Version 0.0.6

Filed under: My Software,Update — Didier Stevens @ 0:00

After searching with base64dump for encoded strings in this maldoc sample, I decided to add an option to base64dump to check all encodings automatically.

Use option -e with value all to try out all encodings, and report all found strings ordered by increasing length. And with option -u, you can limit the output to unique decoded strings.

zipdump.py -s 5 -d output.docx.vir.zip | base64dump.py -e all -u

20170221-202720

base64dump_V0_0_6.zip (https)
MD5: CDC956FAFD7AC2A86C9CD40EC188C7FC
SHA256: BFBCFA51DDC47793C8CA397B261E036701543610F637CE8813BC5870FC4B2C2F

Tuesday 31 January 2017

Update: zipdump.py Version 0.0.5

Filed under: My Software,Update — Didier Stevens @ 0:00

A small feature in this new version: start the -E option value with # to count and group.

Example:

C:\Demo>zipdump.py -E “#%HEADASCII%;%HEADHEX%” Book1.xlsm
1: –…………..;d0cf11e0a1b11ae10000000000000000
1: <xml xmlns:v=”ur;3c786d6c20786d6c6e733a763d227572
12: <?xml version=”1;3c3f786d6c2076657273696f6e3d2231
zipdump_v0_0_5.zip (https)
MD5: 5F49895D3EA97A870ECB1E262A738A04
SHA256: E16CE5A426840D2804E5EF544CF334715F501D0892496D02B6C5000B18CE10BA

Sunday 29 January 2017

Update: FileScanner Version 0.0.0.4

Filed under: My Software,Update — Didier Stevens @ 0:00

I released this new version of FileScanner at the end of 2015, but forgot to announce it here on my blog.

This new version also scans Alternate Data Streams.

FileScanner_V0_0_0_4.zip (https)
MD5: 4BB8F475328B9EB214E6B9405F84816E
SHA256: 5D3B1408C5D2BD17C0441D0D9D0DA565E8D690DE792971092956F4CA10D5A071

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