Hi there,

We are sometimes requested to find out which process sends a certain packet. This generally stems from security concerns (like seeing some TCP session attempts on firewall/IDS device logs etc). Even though it may not be exactly possible to tell which process sends a certain packet always, most of the time we can find the process name without any live debugging etc)

So here are some methods to identify the process sending a certain packet out to network:

1) Network Monitor (For any OS version)

Network Monitor 3.x can show you the process name most of the time correctly (even though there could be some situations when you cannot identify the process)

 

Note: You can download the latest Network Monitor version at the following link:
http://www.microsoft.com/downloads/details.aspx?displaylang=en&FamilyID=983b941d-06cb-4658-b7f6-3088333d062f

2) Process Monitor (For any OS version)

Process Monitor can also display process name for TCP/UDP activity


Note: You can download Process Monitor tool at the following link:
http://technet.microsoft.com/en-us/sysinternals/bb896645.aspx 


3) For Windows 7 / Windows 2008 R2

You can use the new built-in ETL tracing available at NDIS layer. All you need to do is to start a new ETL packet capturing session. This method doesn't even require you to install any sniffing software (Network Monitor/Wireshark etc). You can use this option for general packet capturing on Windows 7/Windows 2008 R2 as well:

netsh trace start capture=yes tracefile=c:\temp\capture1.etl

<<Repro the behavior>>

netsh trace stop

Note: You'll need to open the created ETL file with Network Monitor 3.3/3.4



4) For Windows XP/2003

=> You can use the following method to find out the process if it's a TCP or UDP packet

A. To enable the kernel logger and have it generate a log file of TCP/IP activity, follow these steps:

1. Run the Performance Tool, and select the Performance Logs And Alerts node.
2. Select Trace Logs, and then select New Log Settings from the Action menu.
3. When prompted, enter a name for the settings (for example, Microsoft Data).
4. On the dialog box that opens, select the Events Logged By System Provider option and then deselect everything except the Network TCP/IP option.
5. In the Run As edit box, enter the Administrator account name and set the password to match it.
6. Dismiss the dialog box, and wait until the event is logged.
7. Once the event is logged, select Stop from the Action menu in Perfmon.
8. Open a command prompt, and change to the C:\Perflogs directory (or the directory into which you specified that the trace log file be stored) and get the

Perfmon trace file from there.

B. Analyze the collected trace file:

1. If you are running Windows XP or Windows Server 20003, run Tracerpt (located in the \Windows\System32 directory) and pass it the name of the trace log file. If you are running Windows 2000, download and run Tracedmp from the Windows 2000 Resource Kit. Both tools generate two files: dumpfile.csv and summary.txt.
2. Rename dumpfile.csv as dumpfile.txt, start Microsoft Excel, click on Menu and Open. In the open dialog box locate the folder where dumpfile.txt is and
change the file type box to text file. dumpfile.txt is visible now, click on it twice. Text Import Wizard pops up. Choose delimited, next, on the next page
check only comma at delimiters, next, select all the columns in the Data preview box and change the Data type to text, finish.
3. Rows starting with Event Name,  EventTrace, SystemConfig contain information about the trace, hardware, running services... etc.
4. Rows starting with UdpIp or TcpIp ...

UdpIp or TcpIP, Send or  Recv, ?, ?, ?, ?, PID, Payload of the transport (byte), Destination IP, Source IP, Destination port, Source port, ?, ?

An example output:

...
       UdpIp,       Send, 0xFFFFFFFF,   129079416141424158,          0,          0,     2136,        8, 172.016.001.001, 172.016.057.015, 2762, 36003, 0, 0
       UdpIp,       Send, 0xFFFFFFFF,   129079416141424158,          0,          0,     2136,        8, 172.027.045.020, 172.016.057.015, 6004, 36009, 0, 0
       UdpIp,       Send, 0xFFFFFFFF,   129079416141424158,          0,          0,     2136,        8, 172.160.076.112, 172.016.057.015, 2344, 36016, 0, 0
       UdpIp,       Send, 0xFFFFFFFF,   129079416141424158,          0,          0,     2136,        8, 172.048.102.066, 172.016.057.015, 1116, 36022, 0, 0
...

- For example, in the first line, 172.016.057.015 host is sending a UDP packet to 172.016.001.001. Packet lenght is 8 bytes and source UDP port is 36003 and

destination UDP port is 2762. And process ID that is sending the UDP packet is 2136. And the tasklist output collected on the same machine was as follows:

...
cqmghost.exe                  4972 Console                    0      4,324 K
svchost.exe                   5024 Console                    0      1,524 K
wmiprvse.exe                  5316 Console                    0      2,192 K
wmiprvse.exe                  5468 Console                    0        976 K
logon.scr                     6080 Console                    0        200 K
mssearch.exe                  6028 Console                    0      5,828 K
wmiprvse.exe                  5176 Console                    0      2,168 K
mad.exe                       7176 Console                    0     45,792 K
AntigenStore.exe             10092 Console                    0        200 K
store.exe                     2136 Console                    0  1,040,592 K
emsmta.exe                   12020 Console                    0     29,092 K
AntigenIMC.exe                1308 Console                    0        200 K
svchost.exe                   6516 Console                    0      1,992 K
...

So the process that was sending the UDP packet was store.exe (process Id:2136)


5) Special scenarios

In some special scenarios, you may not be able to find the process by using the above methods. For example, in a couple of cases I was requested to find out why a certain client was sending so many ARP requests back to back (as it was causing some alarms to be generated by IDS devices and the LAN switch was disabling the switch port after a short while) and none of the above methods helped. Then I decided to do it that way: let us allow the client to do whatever it likes by loosening the existing security settings (like changing switch configuration so that it doesn't disable the port). That way we had a chance to see what the client was doing after those ARP requests. Another similar problem was reported by another customer. They realized that the DCs were trying to get in touch with the clients by using different ports/protocols like TCP 445/139, ICMP, Kerberos etc. Again we led the DC do whatever it tried to do so that we were able to see the activity and hence the process/reason behind that. I'm going to talk about this in another blog post.


Hope this helps

Thanks,
Murat