Wednesday, December 14, 2016 Open Source version released

Today we are officially launching an open source licensed version of - a C command line tool to scan document streams with Yara signatures for exploits and active content as well as Cryptanalysis attacks on XOR obfuscation. Dubbed QuickSand_Lite, this version initially does not include the full Cryptanalysis module, the brute force single byte XOR, or the XOR Look Ahead algorithm.

Github Repo

In addition to the code, we are also including Yara signatures for active content, executables, some CVE exploit identification as well as a selection of general document-related Yara signatures. We've enhanced our Yara signatures with a numeric score which is used to calculate the overall badness score of a sample. Generally 1-10 are active content such as macros, 10+ are exploits or shell commands executed via the active content.

Exploit and Active Content Detection

  • Word
  • Excel
  • Powerpoint
  • RTF
  • Mime MSO xml
  • Emails

XOR + ROL/ROR/NOT/ADD/SUB Embedded Executable Detection

  • Word
  • Excel
  • Powerpoint
  • RTF
  • Mime MSO xml
  • Emails
  • PDF
  • TCP Streams data
  • Any non-executable file which may contain an XOR obfuscated exe

Executable Detection Target OS

  • Windows
  • Mac
  • Linux
  • VBS

XOR DB Cryptanalysis Attack

The XOR-DB functionality uses a dictionary of common XOR keys up to 256 bytes long - ascending, descending, algorithmic, cafebabe variants.

Web version

Our site runs the full version with up to the minute exploit signatures and additional trojan signatures.


Yara 3+ (searching via libyara)
zlib (deflate/uncompress)
libzip (unzip)

OS Compatibility

Designed for Linux and Mac command line. Windows is untested and not recommended for safe malware handling.

Download quicksand_lite Package

Install Script - Dependencies for Mac/Linux


cd quicksand_lite-1.01.001
chmod 777 ./

Coming soon

  • Python integration
  • More exploit and trojan signatures

Full Version and Commercial Licensing



mac:quicksand_lite tylabs$ ./ 

[sample with active content and shell execution]
mac:quicksand_lite tylabs$ ./quicksand.out AELM\ Entertainment\ budget\ and\ Attendance\ allowance.xls 
 -0> root {9}
  qstime:2016:12:14 17:52:32

[sample with 4 byte xor key]
mac:quicksand_lite tylabs$ ./quicksand.out cafebafe.rtf 
 -0> root {6}
  qstime:2016:12:14 17:52:50

  -1> xor {3}

[sample with 256 byte xor key + rol 5]
mac:quicksand_lite tylabs$ ./quicksand.out test2.doc 
 -0> root {7}
  qstime:2016:12:14 17:53:14

  -1> xor {2}

   -2> rol {2}

mac:quicksand_lite tylabs$ 

Tuesday, December 13, 2016

Understanding our online toolkit for phishing document/PDF forensics

Our 3 main online tools for forensic analysis of documents and PDFs are PDFExaminer, Cryptam and


Use PDFExaminer to decode or decrypt all the streams in a suspect PDF, and look for known exploits or active content such as JavaScript or Flash.


PDFExaminer will return a score of over 0 and under 10 for active content, don't trust a PDF with Active Content from emails. Some complicated forms like Passport applications will have a lot of Javascript but are safe. PDFExaminer allows an experienced analyst to drill down to view the actual Javascript. A score over 10 with a CVE-201XX-XXXX exploit ID are definitely bad, don't open those at all. See below "Cryptam and for all non-executable files" for more analysis you can do on a PDF to find obfuscated embedded executables.

Cryptam and for documents

Both  Cryptam and will parse all the various streams that can occur within an Office document such as Word, PowerPoint or Excel plus interchange formats such as RTF and mime MSO xml.


Scores of over 0 but under 10 indicate active content such as Macros or ActiveX controls- again don't trust active content from unknown sources or in emails. Scores over 10 usually mean a Macro executes a shell command or a CVE-20XX-XXXX known exploit was found.

Cryptam and for all non-executable files 

For non-executable files - documents, PDFs, images, TCP streams - Cryptam or attempt to find obfuscated embedded execuables - Windows, Mac, Linux binaries or VBS scripts. Both tools attack the XOR and ROL/ROR/NOT obfuscation using different cryptanalysis techniques and may get different results. Generally, the final results should be very similar between the two tools - if you do find a sample which returns different or no results in one tool but a positive malware in the other, please let us know.


For PDFs and non - documents, Cryptam and will only report if an embedded executable was found - a score of 0 on a PDF only means no executable was found - you'll still need to check the PDFExaminer results for PDF specific exploits. For Office documents, a score of 0 means no known exploits or embedded executables were found.

Errors and Feedback

Contact us if our tools may have missed something and you think a sample is bad, or if we detected something as bad that's actually safe.

Coming Soon to a Command Line Near You

A portable C command line version of, for free, with no web or internet dependencies.
We'll tell you where to find it on GitHub and how it differs from the full commercial version in the next post. Crack some of those pesky 256 byte XOR keys without uploading your secret stash of APT malware samples to us.

Monday, November 7, 2016

QuickSand += structhash

We are pleased to announce version 2 of's structural hashing algorithm "structhash" which can be used to fingerprint the structure of an office document or RTF.

Typical weaponization of malware document's use a skeleton exploit doc as part of the exploit builder process. Usually this skeleton exploit document is specific to to the kit or group behind an attack campaign. The structural hash we've developed takes into account the different streams and any XOR or ROL encoding to build a campaign specific fingerprint. You can then search for the structhash to find additional samples likely related to your campaign.

Early 0 day usage usually follows this model with one group's zero day being outed and other groups replacing the original payload with their own - so the structhash can help find additional samples of a zero day for further analysis.

Despite changes in payloads the underlying core of a malicious document doesn't change that much, the structhash can allow you to track exploits from the same author or exploit kit and reduce your workload attributing samples to campaigns automatically.

Recent APT 28 / Sofacy group / Fancy Bear attacks used the CVE-2016-4117 exploit, looking at a known sample from Palo Alto's Unit 42 report on the "Dealer's Choice" campaign:

DealersChoice.B: SHA256:af9c1b97e03c0e89c5b09d6a7bd0ba7eb58a0e35908f5675f7889c0a8273ec81 structhash is gV9m3kqVr5qe7FY

We can then search for QuickSand structhash gV9m3kqVr5qe7FY:

We then find the second sample sha256: cc68ed96ef3a67b156565acbea2db8ed911b2b31132032f3ef37413f8e2772c5 which also has the structhash of gV9m3kqVr5qe7FY.

As you can see, the structhash can be a powerful tool to group maldocs by campaign. When you are viewing report, click the "root" stream to find the structhash and search for more samples from our sample set here.

Tuesday, September 20, 2016 In Depth - Part 2 The Reports Reports

Today we're going to dig deeper into the document malware analysis reporting, and how the analyst can dig deeper into the results and extracted executables.


The report header contains the information you'd expect - analysis time (for the submitted times you'll have to look at the submissions json page). File hashes. is_malware: 0 for clean, 1 for suspicious active content, 2 for exploits and embedded executables. Score - each yara rule for exploits or active content adds to the score. Runtime - it's fast. And the yara hits - exploits - CVE #, executables windows/mac/VB and whether a PE header is found, and general - the trojan signatures from Malware Tracker. Report Header


The streams section of the report is where you can did deeper into the content and cryptanalysis results. Clicking the headers expands the sections and the indentation shows the object relationships. Grey title are less interesting, red have exploits, and brown have executables.

The distribution item in the root can be very useful. The X's indicate the part of the file where an embedded executable exists. 0 is for null sections, F is for FF sections, 1 is for high entropy areas, and A is for ascii sections such as most of an RTF file.

We are also working on a structural hash structhash of the file which can help find samples from the same attacker or exploit kit. Streams section

DOCX Files

For docx files you'll see the hierarchy of files within the zip,  and embedded OLE files or high entropy data is analyzed for embedded executables as well.

Macros and No Embedded exe's

A lot of the new macro malware won't have an embedded exe, using the distribution results below, we   can see the file is mostly null blocks "0" and does not have enough entropy to have a built in EXE.


The XOR section shows the xorkey for cryptanalysis found keys, or xortkey for a key dictionary result.

XOR block


The Rol section shows the bitwise rol used. You can click the sha256 link for a hex dump of the section, and click (str) for the extracted strings. 

Rol/Ror block

Dropped Files

The dropped files section is similar, click the number (1) to see the hexdump and (str) to see the strings. The strings section can help to get a quick ID of the trojan or find some unique strings for a quick Yara rule.

Tip: hex dumps can be converted back to files: # xxd -r webhexdump.txt > malware.virus

dropped file hex dump

dropped file extracted strings


The bottom of the page has links to a JSON version of the report and a JSON of the submissions (date, original filenames).

Thursday, September 8, 2016 in depth

In addition to our Cryptam tool. We created, a fast C document forensics tool which can conduct cryptanalysis attacks on some XOR ciphers. QuickSand is a CLI, a C Library, and can be wrapped in a web interface.

QuickSand has a lot more user-customizable attack options for special cases while keeping the default analysis as fast as possible.


Known exploits are scanned used embedded Yara, document streams are decoded - hex, base 64, zip, gzip. We don't handle PDF streams - you'll still need for that.

Finding Embedded exe's

XOR+Rol from 20-10 bytes are found instantly with the default cryptanalysis attack.

Optional attacks

XOR Lookahead - where the current byte is xored with the following byte.
Math ciphers - +1 to +255 (equivalent to -1 to -255).
Bitwise not
Brute force 1 byte xor - for when null space is not replaced.
Odd XOR lengths

Example odd xor length:

This sample contains an exe obfuscated with a 21 byte XOR key:
./quicksand.out malware/112c64f7c07a959a1cbff6621850a4ad-2.virus -s 21 -e 50000
 -0> root {3}

  -1> xor {3}

More to follow.

Thursday, July 14, 2016

Document Malware XOR distribution or dial M for Malware

We took a sampling of 5448 recent malware documents with an XOR encoded executable detected by Cryptam. Normally we spend most our time looking at APT samples with 256 byte keys, so the recent results which include quite a bit more crimeware lately were surprising.

26% of samples where encoded with the 1 byte key 0x77, followed by 11.6% 0xFD, and 6.5% 0x6A. In total 59% of samples had a one byte key.
We tried to look into the significance of this high a rate of 0x77. In ASCII, 0x77 translates to a lowercase 'w'. 7 is the country code for Russia, and decimal 77 would be an M in ASCII. According to Wikipedia, during World War II in Sweden at the border with Norway, "77" was used as a password, because the tricky pronunciation in Swedish made it easy to instantly discern whether the speaker was native Swedish, Norwegian, or German.
7.6% of samples were encoded with variants of 0xCAFEBABE, 0xBAFECABE, and 0xFECABEBA. 10% of samples were 4 byte keys.
Only 21% were 256 byte keys. Of those, 42% are an incrementing pattern 000102030405... And 16% are the opposite decreasing pattern FFFEFDFCFB...

As always, you can submit your suspicious documents for analysis with Cryptam here.

Monday, March 9, 2015

0 Detection PDF with external link to malware EXE

This morning Malware Domain List tweeted a 0/57 detection malware PDF which was/is not detected as malware by any AV product on

The PDF has the following attributes:

Original filename: 2015-03-05Label.pdf
Size: 96697 bytes
md5: 0323382619193827959ee85631f6043d
sha1: f64e86177b5b5f8db8a78c346e2a165423b4a427
sha256: bc415d1f0c8d8af1b02008f03788de7e073650893eec01296c537346b42f7244
ssdeep: 1536:s3Orf9OoEPqFlpcTVrGxokqE/3wrqx8TnWOgQSawAgl4a+E7zQGBEkc4ryH:serf9nEUpOJGmTE/BaLJ4qE7EGbmH
content/type: PDF document, version 1.5

Loading the PDF into PDFExaminer does detect an exploit, which is actually more of a "feature" of PDF to link to external content, however, linking to a remote EXE is always bad and probably should be detected in the PDF:

Drilling down to the malicious object in PDFExaminer reveals an external hyperlink to an remote executable:

Now opening the PDF reveals how a user could be exploited, but they still need to click a malicious link to download and execute the malware. So while AV may not protect you from this attack vector initially, about half the AV products tested will detect the downloaded remote executable. User education to avoid clicking suspicious links is a key defence here.

The PDF contents:

AV detection for the remote executable linked to from this PDF is 25/57:

And finally, you can use PDFExaminer for free, online to detect this and other potential threats in PDF documents.