PENETRATION TESTING USES FOR POWER-SHELL
There are a number of uses to which we can put Power-Shell in a penetration testing situation. Since Power-Shell has access to Microsoft’s .NET set of tools, and many of the existing functionality that ships with it is intended for system administration, this provides a great deal of utility to the penetration tester as well.We will go over a few example uses for PowerShell, such as controlling processes and services, interfacing with the event logs, getting and sending files over the network, and interfacing with the Registry.
Controlling processes and services
Since the examples here are very simple, we’ll be working with Power-Shell in interactive mode to run them, something that we have not covered in great detail either in this chapter or in Chapter 1. We can simply issue the commands directly at the prompt in the Power-Shell shell and have the data returned to the console. For example, if we want to get a list of all the running processes on a system, we can execute Get-Process, 1. This will send quite a bit of data scrolling past on our console, considering the large number of processes generally running on a Windows system.
In order to get back something a bit more specific, we can include the process name. To give us an example process to look at, we can start Notepad by simply entering Notepad at the prompt in Power-Shell. We can also specifically use the Start-Process cmdlet to start the process by running StartProcess Notepad. Once Notepad has started, we can get the process information for it by running Get-Process notepad. We should see something similar to that shown in Figure 1 returned as output.
Now that we have a process to work with, we can set about killing it. In Power-Shell, we can kill a process using the Stop-Process cmdlet. Stop-Process can be run using either the process ID or the process name as an argument. If we use the process ID, we can simply run Stop-Process 13768. If we use the process name, we need to add an argument, such as Stop-Process eprocessname notepad.
Working with services is very similar to working with processes. In order to get the list of services, we can run Get-Service. As with processes, Get-Service and the service name will get us the information for a specific service, such as Get-Service Fax. We should see output similar to that shown in Figure 2
The basic information returned from Get-Service will give us the name of the process and its current state. We can then start, stop, or restart the service with Start-Service, Stop-Service, or Restart-Service, respectively. In general, we will need administrative access to manipulate services.
Interfacing with the event logs
Working with the event logs in PowerShell is a very easy task to carry out. Microsoft has given us a simple interface to work with them, although there are a few limitations. Again, we will look at how to work with the event logs in PowerShell in interactive mode, just as we did earlier in this section with processes.
The first thing we are likely to want to do on our target system with the event logs is to look at what we have on the system. For this, we can use the Get-EventLog cmdlet, with the list argument, as in Get-EventLog eList. When we run this cmdlet, we should see output similar to that shown in Figure 3.
Conveniently, once we have the list of event logs in hand, we can use the same cmdlet with a different argument to list the content of a specific log. When we look at a log on a given system, there will likely be a very large amount of information in it, so we will also want to filter what is returned to us, unless we are just dumping the log contents out to a file.We can get the last few messages from the log that we specify by using the enewest argument with Get-EventLog, as in Get-EventLog enewest 5 Application. This will give us output similar to that shown in Figure 4.
We can also clear the event logs quite easily by using the Clear-EventLog cmdlet. To do this, we need to specify the log that we want to clear and the name of the system on which the log resides, as in Clear-Eventlog elog Application
eComputerName . (the space and the period following eComputerName are necessary; without them, this command will not work). This is one area in which we need to be an administrator to run this particular item of PowerShell code. If we are not an administrator, we will get a “permission denied” error message.