W32.Downadup.B

Once executed, the worm checks for the presence of the following registry entries and if not present will create them:

• HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Applets\"dl" = "0"
• HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Applets\"dl" = "0"
• HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Applets\"ds" = "0"
• HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Applets\"ds" = "0"

It then copies itself as one or more of the following files:

• %ProgramFiles%\Internet Explorer\[RANDOM FILE NAME].dll
• %ProgramFiles%\Movie Maker\[RANDOM FILE NAME].dll
• %System%\[RANDOM FILE NAME].dll
• %Temp%\[RANDOM FILE NAME].dll
• C:\Documents and Settings\All Users\Application Data \[RANDOM FILE NAME].dll

It creates a new service with the following characteristics:
Service Name: [PATH TO WORM]
Display Name: [WORM GENERATED SERVICE NAME]
Startup Type: Automatic

Next, it registers as a service by creating the following registry entries:

• HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\[WORM GENERATED SERVICE NAME]\Parameters\"ServiceDll" = "[PATH TO WORM]"
• HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\[WORM GENERATED SERVICE NAME]\"ImagePath" = %SystemRoot%\system32\svchost.exe -k netsvcs
• HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\[WORM GENERATED SERVICE NAME]\"Type" = "4"
• HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\[WORM GENERATED SERVICE NAME]\"Start" = "4"
• HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\[WORM GENERATED SERVICE NAME]\"ErrorControl" = "4"

Note: [WORM GENERATED SERVICE NAME] represents a two word combination taken from a list of the following words:

• Boot
• Center
• Config
• Driver
• Helper
• Image
• Installer
• Manager
• Microsoft
• Monitor
• Network
• Security
• Server
• Shell
• Support
• System
• Task
• Time
• Universal
• Update
• Windows

The worm creates the following registry entry, so that it runs every time Windows starts:
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run\"[RANDOM NAME]" = "rundll32.exe "[RANDOM FILE NAME].dll", ydmmgvos"

Next, the worm deletes any System Restore points created by the user.

The worm then runs a command that speeds up network access on the compromised computer by disabling the Windows Vista TCP/IP auto-tuning to spread more rapidly.

The worm also modifies the following registry entry so that the worm spreads more rapidly across a network:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\"TcpNumConnections" = "00FFFFFE"

Next the worm stops both of the following Windows services:

• Background Intelligent Transfer Service (BITS)
• Windows Automatic Update Service (wuauserv)

The worm then modifies the following file in order to disable the half-open connections limit introduced with Windows XP SP2:
%System%\drivers\tcpip.sys

It also attempts to hide itself on the system by modifying the following registry value:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\explorer\Advanced\Folder\Hidden\SHOWALL\"CheckedValue" = "0"

Next, the worm enumerates available ADMIN$ network shares. It then enumerates the users for those shares and attempts to establish a connection as an existing user, with one of the following passwords:

• 000
• 0000
• 00000
• 0000000
• 00000000
• 0987654321
• 111
• 1111
• 11111
• 111111
• 1111111
• 11111111
• 123
• 123123
• 12321
• 123321
• 1234
• 12345
• 123456
• 1234567
• 12345678
• 123456789
• 1234567890
• 1234abcd
• 1234qwer
• 123abc
• 123asd
• 123qwe
• 1q2w3e
• 222
• 2222
• 22222
• 222222
• 2222222
• 22222222
• 321
• 333
• 3333
• 33333
• 333333
• 3333333
• 33333333
• 4321
• 444
• 4444
• 44444
• 444444
• 4444444
• 44444444
• 54321
• 555
• 5555
• 55555
• 555555
• 5555555
• 55555555
• 654321
• 666
• 6666
• 66666
• 666666
• 6666666
• 66666666
• 7654321
• 777
• 7777
• 77777
• 777777
• 7777777
• 77777777
• 87654321
• 888
• 8888
• 88888
• 888888
• 8888888
• 88888888
• 987654321
• 999
• 9999
• 99999
• 999999
• 9999999
• 99999999
• a1b2c3
• aaa
• aaaa
• aaaaa
• abc123
• academia
• access
• account
• Admin
• admin
• admin1
• admin12
• admin123
• adminadmin
• administrator
• anything
• asddsa
• asdfgh
• asdsa
• asdzxc
• backup
• boss123
• business
• campus
• changeme
• cluster
• codename
• codeword
• coffee
• computer
• controller
• cookie
• customer
• database
• default
• desktop
• domain
• example
• exchange
• explorer
• file
• files
• foo
• foobar
• foofoo
• forever
• freedom
• fuck
• games
• home
• home123
• ihavenopass
• Internet
• internet
• intranet
• job
• killer
• letitbe
• letmein
• login
• Login
• lotus
• love123
• manager
• market
• money
• monitor
• mypass
• mypassword
• mypc123
• nimda
• nobody
• nopass
• nopassword
• nothing
• office
• oracle
• owner
• pass
• pass1
• pass12
• pass123
• passwd
• password
• Password
• password1
• password12
• password123
• private
• public
• pw123
• q1w2e3
• qazwsx
• qazwsxedc
• qqq
• qqqq
• qqqqq
• qwe123
• qweasd
• qweasdzxc
• qweewq
• qwerty
• qwewq
• root
• root123
• rootroot
• sample
• secret
• secure
• security
• server
• shadow
• share
• sql
• student
• super
• superuser
• supervisor
• system
• temp
• temp123
• temporary
• temptemp
• test
• test123
• testtest
• unknown
• web
• windows
• work
• work123
• xxx
• xxxx
• xxxxx
• zxccxz
• zxcvb
• zxcvbn
• zxcxz
• zzz
• zzzz
• zzzzz

Note: Depending on the account lockout settings, multiple authentication attempts by the worm may result in those accounts becoming locked out.

If successful, the worm copies itself to the share as the following file:
[SHARE NAME]\ADMIN$\System32\[RANDOM FILE NAME].dll

It then creates a scheduled job on the remote server to run daily consisting of the following command:
"rundll32.exe [RANDOM FILE NAME].dll, [RANDOM PARAMETER STRING]"

Next, the worm connects to the following URLs to obtain the IP address of the compromised computer:

• [http://]www.getmyip.org
• [http://]www.whatsmyipaddress.com
• [http://]getmyip.co.uk
• [http://]checkip.dyndns.org

The worm creates a firewall rule on the local network gateway device that allows remote attackers to connect to and download from the compromised computer's external IP address through a random port.

The worm then creates an HTTP server on the compromised computer on a random port in the following format:
http://[COMPROMISED COMPUTER EXTERNAL IP ADDRESS]:[RANDOM PORT]

It then sends this URL to remote computers.

The worm then attempts to spread by exploiting the following vulnerability so that remote computers will connect to the above named URL and download the worm:
Microsoft Windows Server Service RPC Handling Remote Code Execution Vulnerability (BID 31874)

The worm then attempts to copy itself to any accessible mapped drive as the following file:
%DriveLetter%\RECYCLER\S-%d-%d-%d-%d%d%d-%d%d%d-%d%d%d-%d\[RANDOM FILE NAME].dll

The worm also attempts to create the following file on any accessible mapped drive so that it executes whenever the drive is accessed:
%DriveLetter%\autorun.inf

It also monitors the compromised computer for any additional new drives and then attempts to infect any newly added drives in the same way.

The worm hooks a number of Windows API calls in order to spread and to make removal more difficult.

The worm also hooks the NetpwPathCanonicalize API and when it is called, it checks the length of PathName in order to avoid exploiting the vulnerability further. If the PathName contains a signature the worm originally has, the PathName may contain an encrypted URL as well from which the worm may download a file and execute it.

The worm patches the following API's in memory:

• DNS_Query_A
• DNS_Query_UTF8
• DNS_Query_W
• Query_Main
• sendto

The worm monitors DNS requests to domains containing any of the following strings and blocks access to these domains so that it appears that the network request timed out:

• ahnlab
• arcabit
• avast
• avg.
• avira
• avp.
• bit9.
• ca.
• castlecops
• centralcommand
• cert.
• clamav
• comodo
• computerassociates
• cpsecure
• defender
• drweb
• emsisoft
• esafe
• eset
• etrust
• ewido
• f-prot
• f-secure
• fortinet
• gdata
• grisoft
• hacksoft
• hauri
• ikarus
• jotti
• k7computing
• kaspersky
• malware
• mcafee
• microsoft
• nai.
• networkassociates
• nod32
• norman
• norton
• panda
• pctools
• prevx
• quickheal
• rising
• rootkit
• sans.
• securecomputing
• sophos
• spamhaus
• spyware
• sunbelt
• symantec
• threatexpert
• trendmicro
• vet.
• virus
• wilderssecurity
• windowsupdate

It contacts one of the following sites to get the current date:

• baidu.com
• google.com
• yahoo.com
• msn.com
• ask.com
• w3.org
• aol.com
• cnn.com
• ebay.com
• msn.com
• myspace.com

It then checks to see whether the date on the compromised computer is on or after January 1, 2009.

The worm will then generate a list of domain names based upon this date in the following format:
[GENERATED DOMAIN NAME].[TOP LEVEL DOMAIN]

Note: [TOP LEVEL DOMAIN] represents the following top level domains:

• .biz
• .info
• .org
• .net
• .com
• .ws
• .cn
• .cc

Note: [GENERATED DOMAIN NAME] represents the domain names created by the worm such as the following example list of domain names generated for January 1, 2009:

• aaidhe.net
• aamkn.cn
• abivbwbea.info
• aiiflkgcw.cc
• alfglesj.info
• amcfussyags.net
• amzohx.ws
• apaix.ws
• argvss.info
• arolseqnu.ws
• asoidakm.cn
• atnsoiuf.cc
• avweqdcr.cn
• axaxmhzndcq.cc
• barhkuuu.com
• bbuftxpskw.cc
• bdykhlnhak.cc
• bdzpfiu.biz
• bijkyilaugs.cn
• bjpmhuk.ws
• bmmjbsjidmt.com
• bzagbiwes.cc
• carse.cn
• cauksxf.biz
• cfhlglxofyz.biz
• cinsns.cc
• ciynbjwm.com
• cljivsb.biz
• cpeadyepcis.biz
• cqnxku.ws
• ctmchiae.ws
• cxjsy.net
• czkdu.net
• dbffky.cn
• dgbdjsb.com
• drpifjfxlyl.ws
• dtosuhc.org
• duahpzq.org
• dwrtwgsm.cn
• dyjomzyz.com
• earuldx.cn
• egqoab.net
• egxbsppn.cn
• ehkvku.cn
• elivvks.net
• emxmg.info
• eobvidij.org
• erwojl.org
• evqvmwgw.cn
• ewioygq.biz
• exxkvcz.cc
• ffaqk.info
• fhlwov.net
• fitjg.net
• fkhbumne.info
• fknacmvowib.cn
• fmdsqasqm.net
• fmgcjv.cn
• fpljpuqp.info
• fsrljjeemkr.info
• fthil.cc
• ftphtsfuv.net
• gbgklrka.cc
• gbmkghqcqy.net
• gbxyu.ws
• gezjwr.biz
• gjbwolesl.info
• glkzckadwu.biz
• gmvhjp.ws
• gsvrglz.cc
• gutvjbektzq.com
• gwtqx.cn
• hbyzvpeadkb.net
• hewdw.ws
• hjcxnhtroh.cn
• hltowx.com
• hqjazhyd.com
• hrmirvid.com
• hudphigb.org
• hvagbqmtxp.info
• idvgqlr.ws
• ihnvoeprql.biz
• iidqkzselpr.com
• ijthszjlb.com
• iklzskqoz.cn
• iqgnqt.org
• iqrzamxo.ws
• isjjlnv.org
• iudqzypn.cn
• iyfcmcaj.cn
• jayrocykoj.ws
• jffhkvhweds.cn
• jfxcvnnawk.org
• jgrftgunh.org
• jguxjs.net
• jhanljqti.cc
• jhvlfdoiyn.biz
• jjhajbfcdmk.net
• jkisptknsov.biz
• jknxcxyg.net
• jlouqrgb.org
• jpppffeywn.cc
• jradvwa.biz
• juqsiucfrmi.net
• jvnzbsyhv.org
• jxnyyjyo.net
• kaonwzkc.info
• kdcqtamjhdx.ws
• kgeoaxznfms.biz
• kihbccvqrz.net
• kimonrvh.org
• kjsxwpq.ws
• kkrxwcjusgu.cn
• knqwdcgow.ws
• koaqe.cc
• kodzhq.org
• kqjvmbst.net
• kufvkkdtpf.net
• kxujboszjnz.ws
• lagcrxz.cc
• lawwb.com
• lbdfwrbz.net
• ljizrzxu.cc
• lmswntmc.biz
• lotvecu.com
• lplsebah.cn
• lxhmwparzc.ws
• lyamwnhh.info
• mciuomjrsmn.cn
• mdntwxhj.cn
• meqyeyggu.cc
• mfigu.cn
• mimdezm.biz
• mkdsine.cn
• mmtdsgwfa.net
• mouvmlhz.cc
• mozsj.biz
• mpqzwlsx.ws
• msvhmlcmkmh.biz
• mtruba.ws
• myrmifyuqo.biz
• naucgxjtu.ws
• ncwjlti.cn
• nertthl.net
• nnxqqmdl.info
• nuxtzd.cn
• nxvmztmryie.ws
• nybxvgb.net
• nzsrgzmhay.net
• oadscrk.org
• oezepyh.info
• ojrswlg.net
• olgjkxih.org
• omqxqptc.ws
• ooudifyw.cn
• opkawiqb.cn
• oqsfz.ws
• orvfkx.cc
• otoajxfn.net
• oxeeuikd.net
• oyezli.com
• pfath.info
• plsexbnytn.com
• poplie.cc
• psbdfflh.cn
• qfmbqxom.ws
• qjvtczqu.com
• qpcizvlvio.biz
• qslhoks.cn
• qtcnfvf.biz
• qtsnk.cn
• qzktamrsgu.cn
• rbhixtifxk.cc
• rccoq.net
• rgievita.ws
• rlrbqpxv.org
• rozhtnmoudg.cc
• rpsctacalyd.cn
• rrmkv.com
• rtpuqxp.net
• rtztoupc.net
• satmxnz.ws
• sbtalilx.com
• sdjnaeoh.cc
• sirkqq.org
• sjkkfjcx.biz
• sjkxyjqsx.net
• stmsoxiguz.net
• tdeghkjm.biz
• tkhnvhmh.biz
• tmdoxfcc.org
• torhobdfzit.cc
• trdfcxclp.org
• tscmbj.net
• tuwcuuuj.com
• txeixqeh.biz
• uazwqaxlpq.info
• ubxxtnzdbij.com
• ucnfehj.org
• uekmqqedtfm.com
• uhtmou.ws
• uhveiguagm.biz
• uoieg.ws
• uttcx.net
• uyhgoiwswn.cc
• uyvtuutxm.cn
• vfxifizf.info
• vupnwmw.biz
• vzqpqlpk.ws
• waeqoxlrprp.org
• wdrvyudhg.cc
• wediscbpi.org
• whgtdhqg.net
• wkstxvzr.org
• wmrgzac.info
• wnwqphzao.info
• wsajx.com
• wskzbakqfvk.org
• wtngipaynh.info
• wumvjpbbmse.cc
• wuzunxevor.info
• wwftlwlvm.org
• xcncp.info
• xeeuat.com
• xhazhbir.biz
• xjnyfwt.org
• xlrqvoqmsxz.info
• xqgbn.cn
• xwrrxwmo.cc
• xxabrkhb.cc
• xxmgkcw.cc
• xxxxgvtaa.com
• xzoycphicpk.com
• ybbfrznr.info
• ycceqdmm.cc
• ydxnochqn.org
• ygmwharv.info
• ylnytttckyc.com
• yuvudlsdop.cc
• ywhaunsyez.cc
• ywxdggnaaad.org
• zindtsqq.ws
• zkywmqx.com
• zoosmv.info
• zqekqyq.cn
• zqked.org
• zsatn.ws
• ztgsd.info
• ztioydng.com
• zzczpujz.biz

The worm then contacts the following remote location based on the domain names generated:
http://[GENERATED DOMAIN NAME].[TOP LEVEL DOMAIN]/search?q=%d

It will then download an updated copy of itself from the above remote location.

The worm may also receive and execute files through a peer-to-peer mechanism by communicating with other compromised computers. These files would need to be seeded into the network of worms by the malware author.