Win32.Sector nella libreria di virus:

A file infector designed to download other modules via the P2P protocol. A payload is implemented as an executable file compressed with UPX that, when launched, initializes data, including the UDP port

GetComputerNameA((LPSTR)&buf[1], &size);
if ( lstrlenA((LPCSTR)&buf[1]) > 2 )
{
    B1 = buf[1];
    Bn = buf[lstrlenA((LPCSTR)&buf[1])];
    LOWORD(PORT) = Bn * B1 + 1060;
}

and the TCP port.

TCP_PORT=PORT+19

Opens a shared memory created by the purity_control_4428 shellcode that contains valid configuration data and pairs of IP addresses and ports (nods) to connect to a P2P network. Then the infector opens the shared hh8geqpHJTkdns6 memory where it saves a list of nodes during the module's operation. The nodes are saved to the Windows system registry.

HKEY_CURRENT_USER\Software\<[a-z]*>\%c%d_%d
%c - PC_SEED
%d—parameter number (addr,port,id_peer,count_answer)
%d—node index

Configuration data of large amount is saved to

%SYSTEM32%\<[a-z]*>\[a-z]*.log

or

%TEMP%\<[a-z]*>\[a-z]*.log

Moreover, the file infector also saves the URL list to

HKEY_CURRENT_USER\Software\PC_SEED*PC_SEED\%d\
where %d indicates a parameter number (url list, signature, data size, and so on).

Then Win32.Sector initializes a public key as follows:

E=
00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00  00 00 00 00 00 01 00 01
 
 
N=
BB D2 96 8E ED 0B 93 8A  82 E4 E9 BC C3 C5 32 72
4C 08 AA 56 9F 2D 64 0F  1B 86 68 0E 2B 62 E9 C6
35 6D 75 B6 32 2D 4F A8  B8 D9 2A 44 8B F0 7F E0
D9 8E BE 66 9D A6 7A 9A  6D E1 45 F1 D3 48 01 0D
39 2E 9D 2A 45 FB 0B FB  1D 96 F3 B7 4F 55 E5 E1
16 5B F7 A1 CC 7C 87 C0  C8 9C EF 4E CE 29 58 E2
99 BD 8A 7A 55 BE B4 1C  D9 79 52 25 D8 28 86 7B
81 39 98 5F 2C 6F 14 BB  A5 6B CE 44 E5 91 93 38
8B 9A C1 74 46 84 E1 26  EC 04 94 96 75 09 E3 B5
88 D6 08 F0 4A B7 84 D3  13 2F 00 CC D5 2A 8C 17
07 09 DE 6F B0 D3 D6 2B  C6 A6 9D 38 18 8C 74 9D
86 16 D5 48 6E 97 32 DB  E1 4E F8 04 A6 00 7C 16
2E 70 1C 23 37 DD 5A 52  76 62 70 D4 86 66 6E DF
0C E9 A1 68 F9 5E E8 DD  09 0C 02 7D 35 D0 54 E7
00 C0 14 9F CE 4A 9F F3  99 50 1A 0B CD CC FF 05
B9 04 12 E2 11 76 2F FF  A4 6E 64 18 E0 D0 7B 3B

After that, the file infector initiates several threads that serve the following purposes:

Injects

The malicious program injects its code into all running processes using VirtualAllocEx/WriteProcessMemory/CreateRemoteThread.

Killing processes and deleting system services

The file infector tries to install its driver as follows:

SYSTEM32\drivers\[a-z]*.sys

Using this driver or by calling the TerminateProcess function, it tries to kill the following processes (if they are running):

• AVPM
• 2GUARD
• A2CMD
• A2SERVICE
• A2FREE
• AVAST
• ADVCHK
• AHPROCMONSERVER
• AIRDEFENSE
• ALERTSVC
• AVIRA
• AMON
• TROJAN
• AVZ
• ANTIVIR
• APVXDWIN
• ARMOR2NET
• ASHAVAST
• ASHDISP
• ASHENHCD
• ASHMAISV
• ASHPOPWZ
• ASHSERV
• ASHSIMPL
• ASHSKPCK
• ASHWEBSV
• ASWUPDSV
• ASWSCAN
• AVCIMAN
• AVCONSOL
• AVENGINE
• AVESVC
• AVEVAL
• AVEVL32
• AVGAM
• AVGCC.AVGCHSVX
• AVGCSRVX
• AVGNSX
• AVGCC32
• AVGCTRL
• AVGEMC
• AVGFWSRV
• AVGNT
• AVCENTER
• AVGNTMGR
• AVGSERV
• AVGTRAY
• AVGUARD
• AVGUPSVC
• AVGWDSVC
• AVINITNT
• AVKSERV
• AVKSERVICE
• AVKWCTL
• AVP
• AVP32
• AVPCC
• AVAST
• AVSERVER
• AVSCHED32
• AVSYNMGR
• AVWUPD32
• AVWUPSRV
• AVXMONITOR
• AVXQUAR
• BDSWITCH
• BLACKD
• BLACKICE
• CAFIX
• BITDEFENDER
• CCEVTMGR
• CFPCONFIG
• CCSETMGR
• CFIAUDIT
• CLAMTRAY
• CLAMWIN
• CUREIT
• DEFWATCH
• DRVIRUS
• DRWADINS
• DRWEB
• DEFENDERDAEMON
• DWEBLLIO
• DWEBIO
• ESCANH95
• ESCANHNT
• EWIDOCTRL
• EZANTIVIRUSREGISTRATIONCHECK
• F-AGNT95
• FAMEH32
• FILEMON
• FIREWALL
• FORTICLIENT
• FORTITRAY
• FORTISCAN
• FPAVSERVER
• FPROTTRAY
• FPWIN
• FRESHCLAM
• EKRN
• FSAV32
• FSAVGUI
• FSBWSYS
• F-SCHED
• FSDFWD
• FSGK32
• FSGK32ST
• FSGUIEXE
• FSMA32
• FSMB32
• FSPEX
• FSSM32
• F-STOPW
• GCASDTSERV
• GCASSERV
• GIANTANTISPYWARE
• GUARDGUI
• GUARDNT
• GUARDXSERVICE
• GUARDXKICKOFF
• HREGMON
• HRRES
• HSOCKPE
• HUPDATE
• IAMAPP
• IAMSERV
• ICLOAD95
• ICLOADNT
• ICMON
• ICSSUPPNT
• ICSUPP95
• ICSUPPNT
• IPTRAY
• INETUPD
• INOCIT
• INORPC
• INORT
• INOTASK
• INOUPTNG
• IOMON98
• ISAFE
• ISATRAY
• KAV
• KAVMM
• KAVPF
• KAVPFW
• KAVSTART
• KAVSVC
• KAVSVCUI
• KMAILMON
• MAMUTU
• MCAGENT
• MCMNHDLR
• MCREGWIZ
• MCUPDATE
• MCVSSHLD
• MINILOG
• MSSECES
• MSSEOOBE
• MYAGTSVC
• MYAGTTRY
• NAVAPSVC
• NAVAPW32
• NAVLU32
• NAVW32
• NEOWATCHLOG
• NEOWATCHTRAY
• NISSERV
• NISUM
• NMAIN
• NOD32
• NORMIST
• NOTSTART
• NPAVTRAY
• NPFMNTOR
• NPFMSG
• NPROTECT
• NSCHED32
• NSMDTR
• NSSSERV
• NSSTRAY
• NTRTSCAN
• NTOS
• NTXCONFIG
• NUPGRADE
• NVCOD
• NVCTE
• NVCUT
• NWSERVICE
• OFCPFWSVC
• OUTPOST
• ONLINENT
• OPSSVC
• OP_MON
• PAVFIRES
• PAVFNSVR
• PAVKRE
• PAVPROT
• PAVPROXY
• PAVPRSRV
• PAVSRV51
• PAVSS
• PCCGUIDE
• PCCIOMON
• PCCNTMON
• PCCPFW
• PCCTLCOM
• PCTAV
• PERSFW
• PERTSK
• PERVAC
• PESTPATROL
• PNMSRV
• PREVSRV
• PREVX
• PSIMSVC
• QUHLPSVC
• QUHLPSVC
• QHONLINE
• QHONSVC
• QHWSCSVC
• QHSET
• RFWMAIN
• RTVSCAN
• RTVSCN95
• SALITY
• SAPISSVC
• SCANWSCS
• SAVADMINSERVICE
• SAVMAIN
• SAVPROGRESS
• SAVSCAN
• SCANNINGPROCESS
• SDRA64
• SDHELP
• SHSTAT
• SITECLI
• SPBBCSVC
• SPHINX
• SPIDERCPL
• SPIDERML
• SPIDERNT
• SPIDERUI
• SPYBOTSD
• SPYXX
• SS3EDIT
• STOPSIGNAV
• SWAGENT
• SWDOCTOR
• SWNETSUP
• SYMLCSVC
• SYMPROXYSVC
• SYMSPORT
• TAUMON
• TMLISTEN
• TMNTSRV
• TMPROXY
• TNBUTIL
• TRJSCAN
• VBA32ECM
• VBA32IFS
• VBA32LDR
• VBA32PP3
• VBSNTW
• VCRMON
• VRFWSVC
• VRMONNT
• VRMONSVC
• VRRW32
• VSECOMR
• VSHWIN32
• VSMON
• VSSERV
• VSSTAT
• WATCHDOG
• WEBSCANX
• WINSSNOTIFY
• WRCTRL
• XCOMMSVR
• ZLCLIENT
• ZONEALARM

Moreover, it attempts to delete the following system services:

• AVP
• Agnitum Client Security Service
• Amon monitor
• aswUpdSv
• aswMon2
• aswRdr
• aswSP
• aswTdi
• aswFsBlk
• acssrv
• AV Engine
• avast! iAVS4 Control Service
• avast! Antivirus
• avast! Mail Scanner
• avast! Web Scanner
• avast! Asynchronous Virus Monitor
• avast! Self Protection
• AVG E-mail Scanner
• Avira AntiVir Premium Guard
• Avira AntiVir Premium WebGuard
• Avira AntiVir Premium MailGuard
• BGLiveSvc
• BlackICE
• CAISafe
• ccEvtMgr
• ccProxy
• ccSetMgr
• COMODO Firewall Pro Sandbox Driver
• cmdGuard
• cmdAgent
• Eset Service
• Eset HTTP Server
• Eset Personal Firewall
• F-Prot Antivirus Update Monitor
• fsbwsys
• FSDFWD
• F-Secure Gatekeeper Handler Starter
• FSMA
• Google Online Services
• InoRPC
• InoRT
• InoTask
• ISSVC
• KPF4
• KLIF
• LavasoftFirewall
• LIVESRV
• McAfeeFramework
• McShield
• McTaskManager
• MpsSvc
• navapsvc
• NOD32krn
• NPFMntor
• NSCService
• Outpost Firewall main module
• OutpostFirewall
• PAVFIRES
• PAVFNSVR
• PavProt
• PavPrSrv
• PAVSRV
• PcCtlCom
• PersonalFirewal
• PREVSRV
• ProtoPort Firewall service
• PSIMSVC
• RapApp
• SharedAccess
• SmcService
• SNDSrvc
• SPBBCSvc
• SpIDer FS Monitor for Windows NT
• SpIDer Guard File System Monitor
• SPIDERNT
• Symantec Core LC
• Symantec Password Validation
• Symantec AntiVirus Definition Watcher
• SavRoam
• Symantec AntiVirus
• Tmntsrv
• TmPfw
• UmxAgent
• UmxCfg
• UmxLU
• UmxPol
• vsmon
• VSSERV
• WebrootDesktopFirewallDataService
• WebrootFirewall
• wscsvc
• XCOMM

Blocking access to websites

The driver creates the following device:

\Device\amsint32
\DosDevices\amsint32

Then it decrypts website address list as follows:

• kaspersky
• eset.com
• f-secure.
• mcafee.
• symantec.
• etrust.com
• trendmicro.
• sophos.
• virustotal.
• agnmitum.
• pandasoftware.
• bitdefender.
• spywareguide.
• windowsecurity.
• virusscan.
• ewido.
• spywareinfo.
• onlinescan.
• drweb.
• cureit.
• virusinfo.
• sality-remov
• upload_virus

After that, the file infector sets IRP handlers to communicate with the driver in user mode. It makes execution of the following commands possible:

• DWORD = 777: enable website blocking
• DWORD = 888: disable website blocking
• DWORD = PID: kill the process with the specified PID

If DWORD=666, buffer contains KeServiceDescriptorTable addresses found by the bot in usermode (table is required to search for NtTerminateProcess).

Sets the driver handler function at \Device\IPFILTERDRIVER.
Thus,

IoBuildDeviceIoControlRequest(0x128058u, DeviceObject, &pfunc, 4u, 0, 0, 0, 0, &IoStatusBlock);

As a result, handler monitors all incoming connections, and, if the corresponding option is enabled, connections to websites from the specified list are blocked.

Infection process

The virus infects hard drives by planting the autorun.inf file as follows:

;xmMgM
[AutoRun]
;foXjogjgAirFrJaIWvWCFYOjVdeptddJqu
;qxltVAjtFsQy 
SHell\Open\defAult=1
OPeN =eromp.exe
;
ShelL\open\cOmmAND =eromp.exe
;elrktM
ShEll\ExploRe\ComMAnD=eromp.exe
;rtLT xwoG 
shElL\autOplAy\ComManD =eromp.exe
;pbmyU igvQEdlfgtjgTs

[AutoRun]
;kWxFMtJjds ntDcm JsyqrhIKdiyp
;flpkohOJMJ
shEll\oPen\dEfauLt=1
;
SHeLl\opeN\CoMMaNd=xsvsf.pif
;
oPEn =xsvsf.pif
SHelL\EXploRe\COmmand = xsvsf.pif
;vWgFu HkdyJEhwpgeiEdbvSCyiYmisLkvq
shell\AuToplaY\coMMaND=xsvsf.pif

It infects all files in the following system registry branches:

• Software\Microsoft\Windows\ShellNoRoam\MUICache
• Software\Classes\Local Settings\Software\Microsoft\Windows\Shell\MuiCache
• Software\Microsoft\Windows\CurrentVersion\Run
• It infects all files on the C drive.

Then it infects all files detected in the following network folders:

WNetOpenEnum
• WNetEnumResource
• WNetCloseEnum

Downloading and running files

Once the computer is infected, the virus connects to P2P resources at specified addresses, downloads executable files, checks the digital signature and saves it to the following file:

%SYSTEM32%\<[a-z]*>\[a-z]*.log or %TEMP%\<[a-z]*>\[a-z]*.log

Every time it is launched, the file infector extracts modules from the configuration file and runs them from the %temp% folder.

The modules are as follows:

• Trojan.DownLoader10.49375
• Trojan.Proxy.26841
• Trojan.Rbrute

P2P downloader and protocol

The protocol consists of a UDP server responsible for node exchange (P2P network's “address–port” lists) and a TCP server that is used to download configuration data. The node list structure looks as follows:

struct tnode
{
  DWORD addr; //ip
  WORD port; //udp port
  WORD w1;
  DWORD id_peer; //bot ID; if the bot has a public IP, then ID is larger than 16000000
  DWORD count_answer; //number of successful requests
  DWORD time; //GetTickCount time
};

UDP server

Every UDP packet has a header that can look as follows:

struct P2P_HEAD
{
  WORD crc16; //checksum of the crc16 message
  WORD len; //message length
};

UDP packets are encrypted with RC4 (the P2P_HEAD value is taken as a key).

To exchange configuration data, the file infector starts sending consecutive requests.

OP_03—request for configuration ID.

The packet has the following structure:

struct OP_03
{
  BYTE ver; //protocol version 4
  DWORD id; //configuration ID
  BYTE op; //0x03 command
  BYTE b4Fh; //0x4F
  BYTE b4Bh; //0x4B
  DWORD size_cfg; //0xFEFEFEFE or packet size
  WORD w1; // 0x0
};

As a reply, the file infector receives the same packet with node configuration ID. If the received ID is smaller than the current one, the following request for configuration is sent:

struct OP_23{
  BYTE ver; //4
  DWORD id; //id cfg
  BYTE op; //0x23
  BYTE b4Fh; //0x4F
  BYTE b4Bh; //0x4B
  BYTE b1; //-2
  BYTE b2; //-2
  BYTE b3; //-2
  BYTE b4; //-2
  DWORD size_cfg; //URL size
};

In reply, the malicious program gets the packet that looks as follows:

struct tcfg_head
{
  DWORD size; //configuration size
  DWORD crc32; //crc32
};
 
 
struct tcfg_sign
{
  BYTE sign[0x100]; //digital signature
};
 
 
struct tcfg_info
{
  DWORD id; //configuration ID
  BYTE b1; 
  BYTE b2;
  WORD w1;
  DWORD size_cfg; //configuration size
};
 
struct tcfg{
  tcfg_head head;  
  tcfg_sign sign;
  tcfg_info info;
  WORD count; //number of URLs in a packet
  BYTE urls[754];//addresses
};

The UDP protocol is used to transfer only configuration packets of small size. If the size exceeds 0x400, the malicious program sends the TCP sever a request to download configuration data.

If configuration IPs are the same, but size values are different, configuration data is either downloaded from a P2P network node or is uploaded to the server via the TCP protocol.

Checking for NAT

To check for NAT, the file infector uses a request with the following structure:

struct OP_FLAG
{
  BYTE ver;// 4
  DWORD id; //id cfg
  BYTE op; //0x1
  DWORD status; //current NAT status
  WORD port; //own UDP port
};

Once the server receives such a packet, it attempts to send the source a request via a new socket at a new local port address. Then it sends the OP_03 packet. If a reply is received, the sever considers NAT to be unavailable and assigns the bot with an ID larger than 16000000. Then the server adds this bot to the list. An outgoing packet has the following structure:

struct OP_01
{
  BYTE ver; //4
  DWORD id; //id cfg
  BYTE op; //0x01
  DWORD id_peer; //ID assigned to the bot
};

Exchanging addresses

To request a new IP address of a P2P network node, the bot sends the OP_FLAG command (op=0x02). In reply, the server sends the following packet:

struct OP_02
{
  BYTE ver; //4
  DWORD id; //id cfg
  BYTE op; //0x02
  DWORD addr; //random IP from the node list
  WORD port; //port from the node list
  DWORD id_peer; //node ID from the node list
};

TCP server

The TCP protocol is used to exchange large data packets. To get configuration data from the server, the following request is used:

struct P2P_CFG_REQ{
    DWORD rnd1;
    DWORD rnd2;
};

The reply has the tcfg structure described above. It is encrypted using RC4 with the purity_control_%x key, where %x indicates head.size.

Basic settings storage

Since the bot cannot modify the payload, it is compressed with UPX. At the same time, configuration data and the list of P2P nodes need to be updated in every infected file. For this purpose, a shellcode is used. It creates and initializes a shared memory with address list and configuration data and uploads the file infector's payload into the memory.