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imp_level |
reliable_n_tries |
reliable_keepalive |
reliable_rtt |
reliable_padding |
reliable_no_keepalive |
m2b_raw |
psk |
key |
Once the incoming data is authenticated and decrypted, the driver passes it to the DLL by using memory pipes. |
For example, on HTTP traffic arrival it may send traffic data into a memory pipe \Device\NamedPipe\isapi_http, and then, |
send a received peer-2-peer command message write_peer_nfo=[IP_ADDRESS:PORT]0frag_no_scrambling=Y0 into |
another memory pipe called \Device\NamedPipe\isapi_dg. |
In order to log its activity, the driver writes log data into the pipe \Device\NamedPipe\isapi_log, so that the DLL could log the |
data into the log files. |
Full list of the named pipes used for communications is provided below: |
\Device\NamedPipe\isapi_http |
\Device\NamedPipe\isapi_log |
\Device\NamedPipe\isapi_dg |
\Device\NamedPipe\services_control |
Messages submitted into the pipes are wrapped into the structures. The structures appear to contain headers to allow the pipe |
server, that runs within an infected userland module, to identify the messages first and then unwrap the structures accordingly. |
For example, the message headers could be: |
domc.np |
frag.np |
Once received from the pipes and unwrapped/decoded, the data is then handled by the usermode DLL as per the data intention - |
whether it |
s a traffic sniffing task, a peer-2-peer client logic, a logging task, or a task of saving received files into the virtual volumes. |
BAE Systems Applied Intelligence: Snake Rootkit Report 2014 19 |
VIRTUAL FILE VOLUMES |
The driver creates virtual file volumes for encrypted storage of its files and configuration data: |
\\.\Hd1 |
\\.\Hd2 |
The volumes are mounted from the virtual file systems RawDisk1 and RawDisk2. |
The first partition is created with the following steps: |
the driver creates a 100Mb (0x6400000 bytes) file %windows%\$NtUninstallQ817473$\hotfix.dat by calling |
IoCreateFile() API |
then it creates a section object with the flags SEC_COMMIT and SEC_NOCACHE (0x18000000) by calling |
ZwCreateSection(); the flags mean the file is mapped into memory, the entire range of pages will be committed |
next, it maps a view of the created section into the virtual address space by calling ZwMapViewOfSection() |
finally, it creates device \Device\RawDisk1 from the section map and mounts it as \\.\Hd1 |
The hook installed by the rootkit on IofCallDriver() API provides on-the-fly data encryption/decryption whenever that data is |
written to or read from the volume. The encryption algorithm is based on CAST-128, with the hard-coded key stored in the rootkit |
body. |
As a result, whenever the data is saved into the volume Hd1, it will be scrambled on-the-fly, and reflected in the persistent storage |
file hotfix.dat, which is physically located within the rootkit |
home |
directory: |
Z:\WINDOWS\$NtuninstallQ817473$>dir |
Volume in drive Z has no label. |
Volume Serial Number is 2479-98AC |
Directory of Z:\WINDOWS\$NtuninstallQ817473$ |
13/02/2014 04:47 PM <DIR> . |
13/02/2014 04:47 PM <DIR> .. |
03/02/2014 01:57 PM 210,944 fdisk.sys |
13/02/2014 04:47 PM 104,857,600 hotfix.dat |
2 File(s) 105,068,544 bytes |
2 Dir(s) 8,406,433,792 bytes free |
Analysis of the hotfix.dat file contents reveals it |
s a fully encrypted file with flat entropy. Thus, it is not possible to reveal the |
contents of the Snake |
s volume by accessing the contents of this file (unless the encryption is broken, that is). |
Enlisting the contents of the created volume is possible, along with creating files on it: |
C:\>echo Test > \\.\Hd1\Test.txt |
C:\>type \\.\Hd1\\Test.txt |
Test |
C:\>dir \\.\Hd1\\ |
Volume in drive \\.\Hd1 has no label. |
Volume Serial Number is BA9B-99E8 |
Directory of \\.\Hd1 |
14/02/2014 02:22 PM 7 Test.txt |
1 File(s) 7 bytes |
0 Dir(s) 0 bytes free |
BAE Systems Applied Intelligence: Snake Rootkit Report 2014 20 |
However, as soon as IofCallDriver() hook is removed, the same |
command will fail, as with no hook the rootkit cannot |
decrypt the scrambled volume: |
C:\>dir \\.\Hd1\\ |
Incorrect function. |
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