The upcoming version 0.8.0 version of the Profiler features computation of entropy and the representation of it through a graphical plot. The algorithm used for the calculation is the one described by Ero Carrera on his blog.
When foreign data is present in a file, its entropy is automatically calculated. This is very important, because foreign data can be completely harmless and entropic analysis hugely helps evaluating the risk factor of it.
In this case the analyzed PDF contains 0x0A separators between objects and since it contains many objects, there’s also a lot of foreign data. However, since the entropy is extremely low, it is possible to assume that the foreign data doesn’t have a purpose.
Let’s take a look at a malicious PDF with foreign data. As one can see, the entropy is very high in this case.
Of course, it’s also possible to calculate the entropy in any hex view of a custom range of bytes and block size through the action Data->Entropy. This is the entropy for an entire malicious PDF with a block size of 256 bytes.
The encrypted malware begins at the position where the entropy raises and remains steady.
In the future the plot control will be exposed to the Python SDK so that plugin writers can use it too.
The Info-Tech Storage Format (ITSF) is the primary format that has been adopted by Microsoft for online help files since Windows 98. Due to its popularity, it has been used (and exploited) by many other third parties, mostly because of the support provided by documentation utilities like Doxygen.
With the upcoming 0.8.0 release, the Profiler comes with full compatibility for the following file extensions: CHM, CHI, CHQ, CHW, KPD.
Despite the name (Microsoft Compiled HTML Files), the image above shows the Profiler analyzing a CHM containing not only HTML, but also fonts and PDF documents. These files tend to contain a lot of information, and may require you to increase the unpack limit from the settings.
In the upcoming 0.8.0 version of the Profiler it will be possible to print out the matches of PDF object searches. This comes very handy during analysis if we want to know, for instance, all values for a given key. The option can be activated in the initial configuration dialog.
In this case we’re going to search for URI keys (which specify links).
URI search has also been added as a predefined search.
While the Profiler was designed for document analysis and currently has virtual memory limitations, let’s see how it performs with a Zip bomb. 🙂
A friend of mine linked me the Zip file on this page.
The file contains 16 zipped files, which again contains 16 zipped files, which again contains 16 zipped files, which again contains 16 zipped, which again contains 16 zipped files, which contain 1 file, with the size of 4.3GB.
That’s 16^5 or 1048576 files. If we try to scan it with the Profiler, it will just take endless time trying to scan all the files. It won’t crash nor exhaust memory, just take ages. But we want to analyze the file right now, so how do we do it?
It’s very easy. By default the Profiler has quite a huge nesting limit (10), we can decrease that limit from the Setup -> Limits page. The nesting limit tells the Profiler at which depth of embedding/referencing the scan should stop.
In this case I have decreased it to 1, but 2 or 3 would still have been reasonable. A value of 1 means that only files at the first level will be analyzed. By inserting a value of 0, the file will be opened without any scanning of sub-files.
But what if we want to analyze more in depth one or more branches in the hiearchy? The nesting limit applies only to automatic analyzes, not to manual ones, which means that we can activate items and get the analysis for them (and their children).
As you can see, we’re now analyzing the Zip bomb at the fourth level of nesting. 🙂
The upcoming version 0.7.9 of the Profiler features support for the still to be publicly released PDF symmetric encryption revision 6. While the PDF specifications are not yet freely available, Adobe has already started supporting the new standard.
This is part of our effort of keeping the product up-to-date with the latest standards.
Among other additions, the new 0.7.8 version of the Profiler features support for Zip archives and an improved interface for displaying the file hierarchy.
The supported decompression methods are Deflate and BZIP2 (more will be added). All popular encryption technologies are supported: ZipCrypto and WinZip AES. Support for the undocumented and proprietary PKWare encryption technology is still missing.
One of the handy UI improvements is the in depth risk report.
In this case the global risk signals that the calculated risk is 45% but could be more because some files could not be analyzed, since their format is not supported. This risk reporting is available both for the global risk and individual files.
In this case the main file “nested_crypto.zip” was decrypted but the decryption of the embedded file “test.zip” failed, because I didn’t enter the password for it. We can see that “test.zip” has not been decrypted (nor the files it contains) because of the e character next to the risk percentage. The meaning of these kind of characters is explained by the tooltip.
The Zip format covers an enourmous amount of extensions and hugely increases the usefulness of the Profiler. Enjoy! 😉