This is a continuation of our previous article on performing a Windows triage--however this time we will try to avoid using native Windows tools. Note that there are lots of GUI tools that can help perform basic forensics, however we use mostly command line tools or options as it does not trample on evidence as much as the GUI tools and it makes writing the data to a file easier for offline analysis. We will continue with the same premise as before:
So, you are surfing the web, checking your email, and performing other daily tasks… $#@!, you just realized you clicked a link, opened an attachment, or visited a site that you probably should not have. So what do you do? Cry a little or take action?
Perhaps a friend, family member or neighbor approaches you and asks you to help them “fix their computer” or they say, “I think I have been hacked!”
Whatever the scenario, we have outlined some steps--using mostly Non-native Windows binaries--that you can follow in order to do a little preliminary analysis to detect potential compromise and triage the system
Indicators of Compromise Covered
- Network Connections
- Common File Locations
- Home Directory
- Persistence Mechanisms
- Startup Directory
If your relative/friend or family member is remote, you will most likely have to send the output to a file or have them read it to you (good luck with that if they aren’t technical), but it is a start.
Note: If you cannot coach family members to get to the cmd prompt--all hope may already be lost ;)
The following tool, pslist, is from Mark Russinovich (of sysinternals--now Microsoft). Pslist can be downloaded from http://technet.microsoft.com/en-us/sysinternals/bb896682. It will list the process name, process ID (PID), CPU Time and other information.
pslist >> output.txt
C:\>pslist pslist v1.29 - Sysinternals PsList Copyright (C) 2000-2009 Mark Russinovich Sysinternals Process information for PC122: Name Pid Pri Thd Hnd Priv CPU Time Elapsed Time Idle 0 0 1 0 0 3:57:34.937 0:00:00.000 System 4 8 48 340 0 0:01:01.421 0:00:00.000 smss 604 11 3 19 168 0:00:00.031 4:05:30.375 csrss 652 13 12 375 1772 0:00:15.000 4:05:29.265 winlogon 676 13 17 547 7400 0:00:01.171 4:05:29.109 services 720 9 15 261 1664 0:00:03.859 4:05:28.609 lsass 732 9 22 357 3764 0:00:03.968 4:05:28.562 svchost 892 8 14 190 2888 0:00:01.156 4:05:27.890 svchost 960 8 7 235 1640 0:00:02.656 4:05:27.609 svchost 1072 8 67 1251 14668 0:00:20.593 4:05:27.406 svchost 1132 8 6 80 1272 0:00:02.156 4:05:26.875 svchost 1272 8 5 90 1196 0:00:02.781 4:05:26.625 explorer 1408 8 9 330 10304 0:00:15.421 4:05:25.578 VMwareUser 1648 8 1 26 888 0:00:01.000 4:05:23.937 ctfmon 1660 8 1 69 840 0:00:01.546 4:05:23.843 wracing 1680 8 1 19 324 0:00:41.609 4:05:23.687 sqlmangr 1692 8 2 76 1252 0:01:35.203 4:05:23.609 svchost 1808 8 5 107 1272 0:00:03.968 4:05:18.156 inetinfo 1864 8 18 269 3992 0:00:14.140 4:05:17.953 sqlservr 1880 8 21 214 13068 0:00:01.640 4:05:17.859 VMwareService 128 13 3 47 696 0:01:25.015 4:05:14.359 alg 1168 8 6 105 1132 0:00:01.656 4:05:11.046 cmd 1928 8 1 31 2264 0:00:07.937 3:58:41.046 firefox 380 8 12 343 19320 0:00:04.187 2:55:04.140 notepad 1344 8 1 45 1268 0:00:01.531 2:51:28.015 autoruns 1564 8 5 287 12564 0:00:41.437 2:34:45.015 pslist 696 13 2 115 1040 0:00:00.156 0:00:00.250
Pay attention for oddly named processes, and also look at the “Elapsed Time” column – if the oddly named process appears to have the same elapsed time as the bulk of your Windows processes, it’s a clue that it may be starting either at system boot or when you log into the system.
Another option to “pslist” will display the output in a tree format to easily show the parent process and the rest of the process chain.
pslist -t >> output.txt
C:\>pslist -t pslist v1.29 - Sysinternals PsList Copyright (C) 2000-2009 Mark Russinovich Sysinternals Process information for PC122: Name Pid Pri Thd Hnd VM WS Priv Idle 0 0 1 0 0 16 0 System 4 8 48 340 1884 212 0 smss 604 11 3 19 3808 404 168 csrss 652 13 12 375 25740 2144 1772 winlogon 676 13 17 547 51648 4188 7400 services 720 9 15 261 20220 3400 1664 VMwareService 128 13 3 47 17764 2256 696 svchost 892 8 14 190 59652 4728 2888 svchost 960 8 7 235 33644 4148 1640 svchost 1072 8 67 1251 138856 24388 14668 svchost 1132 8 6 80 29572 3496 1272 alg 1168 8 6 105 32288 3536 1132 svchost 1272 8 5 90 30980 3248 1196 svchost 1808 8 5 107 35608 3700 1272 inetinfo 1864 8 18 269 43944 7904 3992 sqlservr 1880 8 21 214 559284 7768 13068 lsass 732 9 22 357 41392 6004 3764 explorer 1408 8 9 330 81936 15356 10304 firefox 380 8 12 343 85196 29884 19320 VMwareUser 1648 8 1 26 27996 2888 888 ctfmon 1660 8 1 69 29208 3008 840 sqlmangr 1692 8 2 76 35200 4804 1252 cmd 1928 8 1 31 30848 980 2264 pslist 152 13 2 115 29292 2628 1040 notepad 1344 8 1 45 30304 3768 1268 autoruns 1564 8 5 287 96192 16500 12564 wracing 1680 8 1 19 7480 1220 324
The next tool--cmdline--will list the PID, processes, command line arguments, and show the full path to the binary (how helpful!). The tool used to be available from www.diamondcs.com.au, however the site seems to be a squatted site that no longer hosts the tool. You may be able to find this from a reputable friend in the business (feel free to look us up at Foundstone and we can send you a copy--malware free!).
cmdline >> output.txt
C:\>cmdline CmdLine - DiamondCS Freeware Console Tools (www.diamondcs.com.au) --- Found 30 processes. -snip- C:\WINDOWS\system32\services.exe  C:\WINDOWS\system32\services.exe C:\WINDOWS\system32\ctfmon.exe  "C:\WINDOWS\system32\ctfmon.exe" C:\Documents and Settings\Administrator\Local Settings\Temp\wracing.exe  "C:\Documents and Settings\Administrator\Local Settings\Temp\wracing.exe" C:\WINDOWS\system32\notepad.exe  notepad test.txt
Once the command has been executed a well trained eye can usually spot something that is odd. If something is unfamiliar, there are many sites that can be used to investigate a binary name such as http://www.processlibrary.com/.
No results from processlibrary.com can be as concerning as a positive bad hit:
Search results for: wracing.exe
Your search "wracing.exe" did not match any documents.
Make sure the search term was spelled correctly.
Examine Network Connections
The following tool, CurrPorts, is from Nirsoft and is available from http://www.nirsoft.net/utils/cports.html. Please see the full manual at the download site for the many options available. We are just listing our favorite options below:
cports /stext cportsoutput.txt
C:\>cports /stext cportsoutput.txt -snip- ================================================== Process Name : wracing.exe Process ID : 1680 Protocol : TCP Local Port : 1750 Local Port Name : Local Address : 192.168.200.53 Remote Port : 443 Remote Port Name : https Remote Address : 188.8.131.52 Remote Host Name : State : Established Process Path : C:\Documents and Settings\Administrator\Local Settings\Temp\wracing.exe Product Name : -snip-
Examine Common File Locations
In terms of examining file locations, there may not be very many tools better than good old native “dir” command. The following command has been natively present in Windows since before the dawn of time, however the options may not be well known to you or your family members. Running the “dir” command with the following syntax will produce a listing that is sorted by the file creation time.
Many files are located here and thus this is a common place for malware to hide among the weeds
dir /o:d /t:c c:\windows\system32 >> output.txt
C:\>dir /o:d /t:c c:\windows\system32 -snip- 01/07/2010 05:48 PM 689,152 xpsp3res.dll 01/07/2010 06:02 PM <dir> en 01/07/2010 06:02 PM <dir> scripting 01/07/2010 06:02 PM <dir> en-us 01/07/2010 06:19 PM 1,676,288 xpssvcs.dll 01/07/2010 06:19 PM 575,488 xpsshhdr.dll 01/07/2010 06:19 PM 117,760 prntvpt.dll 01/07/2010 06:20 PM <dir> XPSViewer 01/07/2010 06:34 PM 2,560 xpsp4res.dll 01/07/2010 07:39 PM 25,966,024 MRT.exe 01/07/2010 07:50 PM 3,706 TZLog.log 2009 File(s) 408,261,849 bytes 52 Dir(s) 2,505,060,352 bytes free
User’s home directory
This is a popular spot for malware to hide because the attacker has permission to write to these locations under the context of the user
dir /a /s /o:d /t:c “%USERPROFILE%” >> output.txt
dir /a /s /o:d /t:c "%USERPROFILE%" -SNIP- Directory of C:\Documents and Settings\Administrator\Local Settings\Temp 01/07/2010 07:00 PM 54,272 Set29F.tmp 01/07/2010 07:42 PM <dir> NDP1.1sp1-KB953297-X86 01/07/2010 07:47 PM 14,010 ASPNETSetup_00002.log 09/13/2010 09:24 PM 8,141 lick_me.jpg 09/13/2010 09:24 PM 37,376 wracing.exe 09/13/2010 09:24 PM 28,160 wracing.dll 09/13/2010 09:28 PM <dir> plugtmp 03/23/2012 01:43 PM <dir> VMwareDnD 03/23/2012 02:54 PM 104 pdracing.tmp -SNIP-
Note: The filenames above are from real malware--we did not make those up.
Malware wants to survive a reboot, and the way this is accomplished is called a “Persistence Mechanism”. Sometimes the persistence mechanism can give away the presence of malicious software on a system. The following persistence mechanisms will be examined:
- Scheduled Tasks
- Startup Directory
Examining services will leverage both native and non-native tools for analysis. The following command has been natively present in Windows for ages. This command is popular to list the started services.
net start >> output.txt
C:\>net start These Windows services are started: Application Layer Gateway Service Automatic Updates COM+ Event System Computer Browser Cryptographic Services DCOM Server Process Launcher DHCP Client Distributed Link Tracking Client DNS Client Event Log FTP Publishing Help and Support IIS Admin IPSEC Services Logical Disk Manager MSSQLSERVER Network Connections Network Location Awareness (NLA) Plug and Play Protected Storage Remote Access Connection Manager Remote Procedure Call (RPC) Remote Registry Secondary Logon Security Accounts Manager Security Center Server Shell Hardware Detection System Event Notification Task Scheduler TCP/IP NetBIOS Helper Telephony Terminal Services VMware Tools Service WebClient Windows Firewall/Internet Connection Sharing (ICS) Windows Management Instrumentation Windows Time Workstation World Wide Web Publishing The command completed successfully.
The command below using psservice (will discuss soon) could also be used, however it is not as concise as “net start”:
psservice query -s start
You will see sample output from this very useful tool in a bit.
The following command has been natively present in Windows since XP and 2003. It will list the process name, process ID (PID), and the keyname for the service.
tasklist /svc >> output.txt
C:\>tasklist /svc Image Name PID Services ========================= ====== ============================================ System Idle Process 0 N/A System 4 N/A smss.exe 604 N/A csrss.exe 652 N/A winlogon.exe 676 N/A services.exe 720 Eventlog, PlugPlay lsass.exe 732 PolicyAgent, ProtectedStorage, SamSs svchost.exe 892 DcomLaunch, TermService svchost.exe 960 RpcSs svchost.exe 1072 Browser, CryptSvc, Dhcp, dmserver, EventSystem, helpsvc, lanmanserver, lanmanworkstation, Netman, Nla, RasMan, Schedule, seclogon, SENS, SharedAccess, ShellHWDetection, TapiSrv, TrkWks, W32Time, winmgmt, wscsvc, wuauserv svchost.exe 1132 Dnscache svchost.exe 1272 LmHosts, RemoteRegistry explorer.exe 1408 N/A VMwareUser.exe 1648 N/A ctfmon.exe 1660 N/A wracing.exe 1680 N/A sqlmangr.exe 1692 N/A svchost.exe 1808 WebClient inetinfo.exe 1864 IISADMIN, MSFtpsvc, W3SVC sqlservr.exe 1880 MSSQLSERVER VMwareService.exe 128 VMTools alg.exe 1168 ALG cmd.exe 1928 N/A firefox.exe 380 N/A notepad.exe 1344 N/A tasklist.exe 1820 N/A wmiprvse.exe 1892 N/A
The non-native tool, psservice.exe, is another tool from Mark Russinovich (of sysinternals--now Microsoft) and can be found at http://technet.microsoft.com/en-us/sysinternals/bb897542. This can be used to function as the “sc” command--however, the advantage of this tool compared to sc is that it can be run remotely using credentials other than the current user. Additionally, it easily provides the binary path and description with one query shown below:
psservice config [service name] >> output.txt
C:\>psservice config webclient PsService v2.24 - Service information and configuration utility Copyright (C) 2001-2010 Mark Russinovich Sysinternals - www.sysinternals.com SERVICE_NAME: WebClient DISPLAY_NAME: WebClient Enables Windows-based programs to create, access, and modify Internet-based files. If this service is stopped, these fun ctions will not be available. If this service is disabled, any services that explicitly depend on it will fail to start. TYPE : 10 WIN32_OWN_PROCESS START_TYPE : 2 AUTO_START ERROR_CONTROL : 1 NORMAL BINARY_PATH_NAME : C:\WINDOWS\System32\svchost.exe -k LocalService LOAD_ORDER_GROUP : NetworkProvider TAG : 0 DEPENDENCIES : MRxDAV SERVICE_START_NAME: NT AUTHORITY\LocalService
If you would like to get all of the services, descriptions, and full paths to the binaries, omit the service name at the end. For example:
Examine Registry Entries and the Startup Directory
In the prior article we used two native Windows binaries to investigate this data, the reg command and dir command. In this article everything can be achieved with one tool--autorunsc. This is another tool from Mark Russinovich (of sysinternals--now Microsoft). It can be downloaded at http://technet.microsoft.com/en-us/sysinternals/bb963902.
autorunsc -l >> output.txt
C:\>autorunsc -l Sysinternals Autoruns v10.06 - Autostart program viewer Copyright (C) 2002-2010 Mark Russinovich and Bryce Cogswell Sysinternals - www.sysinternals.com -snip- C:\Documents and Settings\Administrator\Start Menu\Programs\Startup putbginfo.bat.lnk C:\Documents and Settings\Administrator\Start Menu\Programs\Startup\putbginfo.bat.lnk File not found: C:\TOOLS\bginfo\putbginfo.bat HKCU\Software\Microsoft\Windows\CurrentVersion\Run ctfmon.exe C:\WINDOWS\system32\ctfmon.exe CTF Loader Microsoft Corporation 5.1.2600.5512 c:\windows\system32\ctfmon.exe 5f1d5f88303d4a4dbc8e5f97ba967cc3 (MD5) 99cb7370f16773c8e2d0c86fe805ec638ab126e9 (SHA-1) 5fb24fc7916a6e6b3be7d84cb1684215b266cd1495575c2e5672b8447932e5b1 (SHA-256) wracing C:\Documents and Settings\Administrator\Local Settings\Temp\wracing.exe -installkys c:\documents and settings\administrator\local settings\temp\wracing.exe 862cac1ffae3ca515f1c8588e3c3c394 (MD5) fb38ac1459da93f36be0af0999618a2f643e2fc8 (SHA-1) ede018f2be5f4655d71c0b02db394b4ff332aacc508915de47bcaf2c1db0cc78 (SHA-256) -snip-
With this sample output, we see that “wracing.exe” is in the “C:\Documents and Settings\Administrator\Local Settings\Temp” directory. We suggest you review the file listing of this directory, sorted by file creation time as well to see what other artifacts may be present from the same timeframe.
Malware will often modify the system security settings contained within the Registry to make removal and remediation more difficult such as disabling the firewall or antivirus and other critical system security alerting mechanisms.
The Windows Security Center settings are common targets for malware infections. They are set to allow you to be notified if something happens to your antivirus, firewall, windows updates, etc. Set with a value of “0” the “disable” is turned off – thus the feature is still active and you will be warned if your antivirus or firewall is disabled, etc. If set with a “1” then the “disable” is turned on, and the affected item will no longer report in the Windows Security Center as an item of concern if disabled.
To review the Registry run:
Common items which are disabled by malware include entries similar to those found below:
HKEY_LOCAL_MACHINE\Software\Microsoft\Security Center FirstRunDisabled REG_DWORD 0x1 AntiVirusDisableNotify REG_DWORD 0x0 FirewallDisableNotify REG_DWORD 0x0 UpdatesDisableNotify REG_DWORD 0x0 AntiVirusOverride REG_DWORD 0x0 FirewallOverride REG_DWORD 0x0
If these registries are loaded with a “1” then the item is disabled.
Examine Scheduled Tasks
In the prior article we used two native Windows binaries to investigate this data, the at command and schtasks command. In this article everything can be achieved with one tool--autorunsc. This is the same tool used above to check the registry entries and startup directory. It can be downloaded at http://technet.microsoft.com/en-us/sysinternals/bb963902.
autorunsc -t >> output.txt
This output is far superior to that of at or schtasks because it provides the full bath to the binary, arguments, as well as MD5 and SHA-1 hashes! Wow.
Initial Analysis of the Results
Analysis often takes far longer than the time required to run the commands. However, according to the sample information above, it appears that we have at least two infections on this host. The data below ties everything together.
Malicious software is present in the process list here:
Name Pid Pri Thd Hnd Priv CPU Time Elapsed Time wracing 1680 8 1 19 324 0:00:41.609 4:05:23.687
C:\Documents and Settings\Administrator\Local Settings\Temp\wracing.exe  "C:\Documents and Settings\Administrator\Local Settings\Temp\wracing.exe"
It also has a connection out to a known bad site:
Process Name : wracing.exe Process ID : 1680 Remote Port : 443 Remote Port Name : https Remote Address : 184.108.40.206 Process Path : C:\Documents and Settings\Administrator\Local Settings\Temp\wracing.exe
Malicious files are present in the following directory:
C:\Documents and Settings\Administrator\Local Settings\Temp 09/13/2010 09:24 PM 8,141 lick_me.jpg 09/13/2010 09:24 PM 37,376 wracing.exe 09/13/2010 09:24 PM 28,160 wracing.dll
The persistence mechanism is via the registry:
HKCU\Software\Microsoft\Windows\CurrentVersion\Run wracing C:\Documents and Settings\Administrator\Local Settings\Temp\wracing.exe -installkys c:\documents and settings\administrator\local settings\temp\wracing.exe 862cac1ffae3ca515f1c8588e3c3c394 (MD5) fb38ac1459da93f36be0af0999618a2f643e2fc8 (SHA-1) ede018f2be5f4655d71c0b02db394b4ff332aacc508915de47bcaf2c1db0cc78 (SHA-256) -snip-
There is also a second (most likely unrelated) suspicious task that runs via the scheduler:
Fortunately antivirus programs protect us from most of the threats that are out there, however the bad guys are constantly finding new ways to infect our systems with new malware. Once your system is infected, the only way to be 1000% certain you have found all of the components of the malware is to re-image your system. (Don’t just re-format the hard disk, as some malware such as TDSS is now infecting the disk boot records)
If you decide to go the route of manual cleanup, here are some helpful thoughts to speed you on your journey:
- If you find your system is infected by the malware, first thing you want to do is to disconnect your system from the internet as quickly as possible to prevent additional malware from being placed on your system and to limit the potential data loss.
- Make a backup. Note that some malware will also infect any USB device which is plugged in. This means that inserting a USB hard drive to perform a backup may actually infect it with an active infection component.
- Turn off the system restore. If the malware infected any of the critical operating system areas, the system restore points may contain copies of the infection which you can inadvertently restore to operation if you recover your OS from an infected copy
- My Computer-> Properties->click the System Restore tab-> Click to select the Turn off System Restore check box
- Using a known clean system, change all your passwords. A common target for malware are credentials, which can then be used by the bad guys to access your accounts, perform fraudulent activities, etc.
- Install and Scan your system with latest updated antivirus and anti-spyware software to clean the malware or spyware, be sure to configure the software to prompt you prior to taking action on any suspicious files found.
- Reboot your system and update all the antivirus signatures and again rescan your system your system with antivirus and spyware.
- If your system is still affected by the malware, then a running process may be infected. To solve this issue you need to live boot to a software CD such as BART PE (http://www.nu2.nu/pebuilder/ ) to prevent the process from running. Tools such as HIJACK THIS can be used to clean the system while the process is not running in order to remove the infection.
Food for Thought
If the infection is using rootkit technology, there is a better chance that either the native or non-native Windows tools will reveal that something is amiss--especially if the non-native tool uses non-Windows API calls to gather the information. If nothing shows up as indicators of compromise, but relatives are still convinced they are owned--they may have a healthy dose of paranoia. Either way, they may have to take it in to a shop or wait until the next holiday gathering when you have your fingers on the keyboard for a more in-depth analysis. As always, happy hunting!