Direction – Whether to block traffic leaving the computer (outbound) or coming into the computer (inbound).DisplayName – The friendly name of the firewall rule.The basic properties you need to fill in are: New-NetFirewallRule -DisplayName "Block Outbound Port 80" -Direction Outbound -LocalPort 80 -Protocol TCP -Action Block For example, to block outbound port 80 on a server, use the following PowerShell command: You can set firewall rules with PowerShell as documented by Microsoft. It will block attacks that target low-hanging fruit. If PowerShell is intentionally made to hide itself by calling the binary from another location or by renaming itself, this process will not work. You’ll see the resulting rule in the outbound firewall rule settings: Susan Bradley Netsh advfirewall firewall add rule name=“PS-Deny-All (%f)" dir=out action=block program=“%f" enable=yes ) Susan Bradleyįirewall rule to block PowerShell from internet access You can also build rules for multiple versions of PowerShell:Ĭ:\> for /R %f in (powershell*.exe) do ( netsh advfirewall firewall add rule name=“PS-Allow-LAN (%f)" dir=out remoteip=localsubnet action=allow program=“%f" enable=yes PowerShell should not be removed but rather hardened and logged to ensure it’s used as intended. This can protect your systems from attacks that leverage PowerShell to call command-and-control computers to launch ransomware and other attacks. Remoteip=localsubnet action=allow program="c:\windows\system32\WindowsPowerShell\v1.0\powershell.exe" \Ĭ:\> netsh advfirewall firewall add rule name=“PS-Deny-All" dir=out \Īction=block program="c:\windows\system32\WindowsPowerShell\v1.0\powershell.exe" \ The second rule drops traffic.Ĭ:\> netsh advfirewall firewall add rule name=“PS-Allow-LAN" dir=out \ This first rule below allows PowerShell to access a local subnet. As noted in this SANS forum post, you can block PowerShell from accessing the internet. You can use Windows Firewall to block applications accessing resources. If you have a pre-defined list of restricted substrings or words in application names (for example, “mimikatz” or “cain.exe”), check for these substrings in “Application”.Monitor whether “Application” is not in a standard folder (for example, not in System32 or Program Files) or is in a restricted folder (for example, Temporary Internet Files).If you have a pre-defined application to perform the operation that was reported by this event, monitor events with “Application” not equal to your defined application.If you are using a security event log monitoring solution to monitor events, keep the following in mind: Use this event to detect applications for which no Windows Firewall rules exist. To determine which applications Windows Firewall blocks, first search the event logs for event 5031, which indicates that Windows Firewall blocked an application from accepting incoming connections on the network. However, an IT administrator might want to use the event log to identify blocked applications rather than using the visual pop-ups in the system tray that can be easily missed. Windows machines notify by default when an application is blocked.
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