Digging Into the Nitol DDoS BotnetNitol is a distributed denial of service (DDoS) botnet that seems to be small and not widely known. It mostly operates in China. McAfee Labs recently analyzed a few samples; we offer here the communications protocol and the Trojan’s capabilities.
Most of the samples we encountered were not packed and were very easy to reverse engineer. The Trojan was written in Visual C++ either in a hurry or by an untrained programmer. We found a lot of bugs in the code.
Nitol copies itself to a random filename ******.exe (where every * is a randomized alphabet character) in the Program Files directory. The new file is registered as a service, “MSUpdqteeee,” with the display name “Microsoft Windows Uqdatehwh Service.”
Bot ActivitiesAfter installation, the malware connects to its command server (we found between one and three hardcoded addresses per sample) using a TCP socket and sends a digest of the victim’s computer information.
Both incoming and outgoing packets are 1082 bytes long (including TCP/IP headers, 1028 bytes of raw data) without regard to the actual size of the data.
Larger pictureThe transmission to the server can be described by the following structure:
typedef struct _ComputerInfo{
DWORD Command; // Always “1″ Computer Info.
char LocaleLanguage[0x40];
char ComputerName[0x80];
char WindowsVersion[0x40];
char PhysicalMemorySize[0x20];
char CPU_Speed[0x20];
char Ndis_Version[0x20];
}ComputerInfo;
It appears this information is used mainly to get an estimation of the botnet’s power and diversity. The data can be used to decide what type of DDoS tasks to give this specific bot. However, this is not enough information for the server to decide whether the bot is running on a virtual machine or is being debugged.
After receiving the information, the command server usually returns a command and parameters.
Possible commands:
enum commands{
GenericFlood = 2,
HTTPFlood = 3,
RawDataFlood = 4,
StopRunning = 5,
UninstallAndDie = 6,
DownloadFileFromUrlExecUrl = 16, // ?!?!?!?
DownloadFileFromUrlExecFile = 17,
UpdateBot = 18,
ExecuteIE_NoWindow = 19,
ExecuteIE_ShowWindow = 20
}
DDos AttacksIn the preceding group of commands, the DDoS functionality is represented by GenericFlood, HTTPFlood, and RawDataFlood.
Each of the flood commands implements several other commands:
Larger pictureHere we have command number 2–GenericFlood–followed by the GenericFloodData structure:
typedef struct _GenericFloodData{
char Address[0x80]; // 0×00
DWORD NumberOfMinutesToRun; // 0×84
DWORD NumberOfThreads; // 0×88
DWORD Command; // 0x8C
}GenericFloodData;
enum GenericFloodCommands
{
send_Random_TCP_Data_Every_10_MS = 1,
Send_UDP_Packets_Every_20_MS = 2,
Send_ICMP_Packet_Sleep_Missing = 3,
Open_Socket_Every_500_MS = 4,
Send_UDP_Packets_Every_20_MS_Random_Source_Address_On_Server = 9,
Send_UDP_Packets_Every_20_MS_Random_Source_Address_On_Server_number_of_threads_plus_20 = 16,
Send_UDP_Packets_Every_20_MS_Random_Source_Address_On_Server_number_of_threads_plus_20_no_Passthru = 17,
Send_TCP_Packets_Random_Source_Address_On_Server_number_of_threads_plus_20 = 18,
Send_TCP_Packets_HardCoded_Source_Address_On_Server_number_of_threads_plus_20 = 19,
Same_As_1_20_More_Threads_If_Client_64_If_Server = 20,
Send_UDP_Packets_Every_20_MS_Source_Address_On_Server_number_of_threads_plus_20 = 23,
Send_TCP_Packets_Every_10_MS_Source_Address_On_Server_number_of_threads_plus_20 = 24,
Open_Socket_Send_1000_TCP_Packets = 25,
Connect_Disconnect_loop = 32,
}
Larger pictureNext we have command number 3–HTTPFlood–followed by the HTTPFloodData structure:
typedef struct _HTTPFloodData{
char Address[0x80]; // 0×000
char Path[0x80]; // 0×080 // BUG!!! The second DWORD is also NumberOfMinutesToRun
unsigned short Port; // 0×100
unsigned short dummy; // 0×102
DWORD dummy1; // 0×104
DWORD NumberOfThreads; // 0×108
DWORD IsDummyGetRequest; // 0x10c
DWORD dummy2; // 0×110
DWORD Command; // 0×114
}HTTPFloodData;
enum HTTPFloodCommands
{
Get_Image_Every_50_MS = 5,
Get_HTML_Every_50_MS_OR_GET_WITH_IE = 6, //BUG
Get_HTML_Every_10_MS = 7,
Get_Image_Every_5_MS = 8
}
None of the samples we ran returned the RawDataFloodData, so we don’t have a recording.
Command number 4–RawDataFlood–should be followed by the RawDataFloodData structure:
typedef struct _RawDataFloodData{
char Address[0x80]; // 0×000
char Buf[0x208]; // 0×080 // BUG!!! The second DWORD is also NumberOfMinutesToRun
DWORD NumberOfThreads; // 0×288
DWORD Command; // 0x28C
}RawDataFloodData;
RawDataFlood takes two possible commands: SendUDPData and SendTCPData. To use SendUDPData you need to set the command parameter to 21, else SentTCPData will be used. Both commands interpret the Buf parameter as a null-terminated string.
We encountered two important bugs:
•It looks like the function to stop the attack after a certain amount of minutes was designed to work with the GenericFlood command and only later was also used for the HTTP and RawData floods, so it uses unrelated data as the amount of time to wait in seconds (always using the DWORD at offset 0×84 from the start of the parameters structure).
•The function in charge of getting the path to the Internet Explorer executable concatenates the string coming back from the GetWindowsDirectory function (usually c:\Windows) to “\Program Files\Internet Explorer\iexplore.exe,” which is normally not the path to the IE executable. The problem resides in the HTTPFlood’s command 6, which performs an infinite loop of running IE from that path.
The following recording shows the traffic of the ICMP attack.
Larger pictureThe following recording shows the traffic of the UDP attack.
Larger pictureOther CommandsStopRunning: Stops current DDoS attacks
UninstallAndDie: Unregisters the service, runs another process to delete the file, and exits the current process
DownloadFileFromUrlExecUrl: Looks like another bug, downloads a file from a URL to a local temp file, then tries to execute the URL
DownloadFileFromUrlExecFile: Downloads a file from a URL to a local file (random name in %temp% “*****.exe”) and executes the file using WinExec API call
UpdateBot: Downloads a file from a URL to “%temp%\stf******.exe.” If download succeeds, deletes the service, executes the file, and exits. (The current version is not deleted from the disk.)
ExecuteIE_NoWindow: Executes Internet Explorer with command-line arguments supplied by the server, doesn’t show the IE window
ExecuteIE_ShowWindow: Executes Internet Explorer with command-line arguments supplied by the server, shows the IE window
Command ServersWe identified the following command server domain names:
zwx5060.3322.org: 121.235.113.52
guangkuo119.3322.org: 125.211.195.29. Targets some diet products hosted on godaddy.com
yezi999.3322.org: 125.211.195.29. Targets some diet products hosted in Hong Kong
kankan902.3322.org: 118.126.16.81
maple110.3322.org: 121.10.24.74
mybaccy.3322.org: 58.221.58.148. Targets a site in China
bcl5736120.3322.org: 121.12.172.67
ylddos.3322.org: 67.215.65.132. This American IP address is registered to opendns.com
xiong97.3322.org: 124.236.128.136
xinxin168.3322.org
sousou123.3322.org
maguss.3322.org
aisini1314.3322.org
fuck0313.6600.org
ksattack.6600.org: 116.255.180.34
fangqi.6600.org
xin9liao.gnway.net
fangqi.7766.org
1.ccddos.net: 182.16.1.42. Hong Kong
rvbwtbeitwjeitv.com: 50.62.3.118. American IP for godaddy.com
rterybrstutnrsbberve.com: 82.165.39.88. German IP for domain registered to a Russian individual
erwbtkidthetcwerc.com: 82.165.39.88
(All the nonspecified IP addresses are in China.)
As we can see, most of the hardcoded domain names are resolved by Chinese dynamic DNS services.
I would like to thank my colleagues Zheng Bu and Benjamin Cruz for their input. Orginal article: Thursday, April 19, 2012 at 1:30pm by Itai Liba
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