show active network connections and processes | Windows

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For a quick overview of which programs or services have an active network connection, they can be listed via simple commands or monitored and analyzed via specific tools. 

PowerShell: Get-NetTCPConnection

As an alternative to the CMD command "netstat", the command "Get-NetTCPConnection" can be used in PowerShell to display the network connections. The following command line combines Get-NetTCPConnection with Get-Process and Out-GridView. The result is a list of all incoming and outgoing network connections and their processes.

The following line can be easily pasted (Ctrl+C) into Windows PowerShell via the clipboard (Ctrl+V):

 Get-NetTCPConnection | Where-Object state -ne Bound | Select-Object LocalAddress,LocalPort,RemoteAddress,RemotePort,State,OwningProcess, @{n="ProzessName"; e={( Get-Process -Id $_.OwningProcess).ProcessName}} | Out-GridView

Thanks to Out-GridView, the displayed network connections can be easily sorted and filtered:

(Here connection from Microsoft Edge to a web page with port 443)

Legend:

LocalAddress local network address (own address)
own IP address or 0.0.0.0 (::) for any address
LocalPort local network port
RemoteAddress Remote device network address
RemotePort Network port of the remote device
OwningProcess Process ID (PID) of the service which establishes or receives the connection.
ProzessName ProcessName of "Get process"

State

Listen wait for connection
Mostly on any own address (0.0.0.0) and a local port. A connection can be established from a remote device to the local port listed here.
Bound Socket created (bind), but no further call (listen, accept, connect, close)
Established

Connection established

  • For outgoing the remote address and the remote port as well as the process name are interesting. (LocalPort: HighPort)
  • For incoming connections, e.g. a web service on the local PC with port 80
    LocalAddress: IP of the local device; LocalPort: 80, RemoteAddress: IP address of the remote device, RemotePort: HighPort 
SynSent

outgoing connection attempt

SynReceived

incoming connection attempt

Closing Both sockets finished, but not all data sent yet
CloseWait The remote device has terminated the connection
Closed Socket is not used
TimeWait Socket waits after closing to still process packets on the network
LastAck The remote device has terminated the connection, the socket is closed, wait for confirmation
FinWait1 Socket is closed and the connection is terminated
FinWait2 Connection terminated, socket waits for remote device to terminate

How does the command line compose itself, in order

Get-NetTCPConnection shows all active network connections of the PC:

PS C:\Users\LiBe> Get-NetTCPConnection

LocalAddress                        LocalPort RemoteAddress                       RemotePort State       AppliedSetting
------------                        --------- -------------                       ---------- -----       --------------
::                                  445       ::                                  0          Listen
::                                  135       ::                                  0          Listen
...
192.168.1.198                       49808     116.203.238.206                     443        Established Internet
....

As usual in PowerShell, a pipe and "where" can be used to filter specifically:

PS C:\Users\LiBe> Get-NetTCPConnection | where RemoteAddress -Like "116*"

LocalAddress                        LocalPort RemoteAddress                       RemotePort State       AppliedSetting
------------                        --------- -------------                       ---------- -----       --------------
192.168.1.198                       49827     116.203.238.206                     443        Established Internet

In the standard output the process ID is missing, this can be displayed as follows:

PS C:\Users\LiBe> Get-NetTCPConnection | where RemoteAddress -Like "116*" | Select-Object LocalAddress,LocalPort,RemoteAddress,RemotePort,State,OwningProcess | Format-Table

LocalAddress  LocalPort RemoteAddress   RemotePort       State OwningProcess
------------  --------- -------------   ----------       ----- -------------
192.168.1.198     49843 116.203.238.206        443 Established          6224

The Get-Process command can be used to read the ProcessName for the PID.

PS C:\Users\LiBe> Get-Process -Id 6224

Handles  NPM(K)    PM(K)      WS(K)     CPU(s)     Id  SI ProcessName
-------  ------    -----      -----     ------     --  -- -----------
    288      19    10924      24952       1,89   6224   1 msedge

combined:

PS C:\Users\LiBe> Get-NetTCPConnection | Select-Object LocalAddress,LocalPort,RemoteAddress,RemotePort,State,OwningProcess, @{n="ProzessName"; e={( Get-Process -Id $_.OwningProcess).ProcessName}} | Format-Table

LocalAddress  LocalPort RemoteAddress   RemotePort       State OwningProcess ProzessName
------------  --------- -------------   ----------       ----- ------------- -----------
::                49670 ::                       0      Listen           708 services
::                49669 ::                       0      Listen          2760 spoolsv
::                49668 ::                       0      Listen          2096 svchost
...
::                49665 ::                       0      Listen           600 wininit
::                49664 ::                       0      Listen           744 lsass
::                  445 ::                       0      Listen             4 System
::                  135 ::                       0      Listen           992 svchost
0.0.0.0           49849 0.0.0.0                  0       Bound          6224 msedge
0.0.0.0           49848 0.0.0.0                  0       Bound          7744 msedgewebview2
0.0.0.0           49847 0.0.0.0                  0       Bound          7744 msedgewebview2
0.0.0.0           49846 0.0.0.0                  0       Bound          7744 msedgewebview2
....
0.0.0.0           49713 0.0.0.0                  0       Bound          8700 SystemSettings
0.0.0.0           49707 0.0.0.0                  0       Bound          6224 msedge
0.0.0.0           49673 0.0.0.0                  0       Bound          2716 svchost
192.168.1.198     49849 116.203.238.206        443 Established          6224 msedge
192.168.1.198     49820 40.97.120.130          443 Established          5252 SearchHost
192.168.1.198     49707 192.168.1.166         8009 Established          6224 msedge
192.168.1.198     49673 20.199.120.85          443 Established          2716 svchost
...

netstat: Windows / Linux

The netstat command is available in both Linux and Windows and provides the ability to view all network connections and open ports. It is called in Windows from the command prompt, by entering the following command:

netstat -ano 

The parameters -ano mean:

  • a means: all connections
  • n: Addresses and port numbers numeric
  • o: additionally display the PID (i.e. which process is behind it)

the status

LISTENING means: The client listens for this port. It therefore waits until another network device establishes a connection to it. 

SYN_SENT: The client is establishing a connection and waiting for the response.

ESTABLISHED according to: Connection established.

Filter

If the output should contain too many entries, the output can be filtered by the command "find", i.e. 

netstat -ano | find "FILTER"

Processes

With the parameter /b netstat tries to display the underlying process based on the PID, for this administrator rights are required:

TCPView

With the free tool TCPView, similar to Get-NetTCPConnection, all connections can be displayed. The tool consists of a simple .exe file and does not need to be installed.

technet.microsoft.com/de-at/sysinternals/bb897437.aspx

CurrPorts

The tool CurrPorts from nirsoft, which is also free of charge, offers an extended range of functions. The additional functions include notification of new connections, filters and the option to record a log file. CurrPorts also consists of a simple exe file and, like TCPView, does not need to be installed.

Certain services can be excluded by right-clicking and "Exclude in Filter", or only certain services can be observed with "Include in Filter".

 An autorefresh interval can be set so that the view is refreshed automatically:

Tooltip notification via "Tray Balloon On New Ports

 

Browser - Inspect

To view the communication of the browser when calling a web page, all modern browsers include the ability to make network calls visible. In Google Chrome, Internet Explorer, Firefox and Microsoft Edge with a "right click" on the web page and: "Examine element".

in the Network tab the loaded elements are displayed:

 

Wireshark

Wireshark is an extremely powerful tool. The open source program offers experienced users the possibility to analyze network traffic in detail. However, Wireshark is not only suitable for specialists. Thanks to the numerous filters and functions, anyone should be able to get an overview of the network traffic very quickly:

For example, under Statistics / Endpoints, all devices to and from which a network connection has been initiated can be displayed:

Windows Performance Toolkit

A trace from the operating system's point of view can be created using the Windows Performance Toolkit. In addition to the processes and events, their network communication is also logged, as an example for a logon trace

Conclusion

For a quick overview of active network connections, a simple command in PowerShell: Get-NetTCPConnection or the netstat command prompt is sufficient. For a better overview or more details, special programs can be used, up to the network sniffer: Wireshark, which can record the complete network traffic.

 

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