How To Check If Firewall Is Blocking A Port In Windows 10

In the process of filtering Net traffic, all firewalls have some type of logging feature that documents how the firewall handled various types of traffic. These logs can provide valuable information similar source and destination IP addresses, port numbers, and protocols. You can as well apply the Windows Firewall log file to monitor TCP and UDP connections and packets that are blocked by the firewall.

Why and When Firewall Logging is Useful

To verify if newly added firewall rules work properly or to debug them if they do non piece of work every bit expected.
To determine if Windows Firewall is the cause of awarding failures — With the Firewall logging feature you can check for disabled port openings, dynamic port openings, analyze dropped packets with push and urgent flags and analyze dropped packets on the send path.
To assistance and identify malicious activity — With the Firewall logging feature you lot tin can check if any malicious action is occurring within your network or not, although you must remember it does not provide the data needed to rails down the source of the activity.
If you notice repeated unsuccessful attempts to access your firewall and/or other high profile systems from one IP accost (or group of IP addresses), so y'all might want to write a rule to drop all connections from that IP space (making certain that the IP address isn't being spoofed).
Outgoing connections coming from internal servers such every bit Web servers could exist an indication that someone is using your organisation to launch attacks against computers located on other networks.

How to Generate the Log File

By default, the log file is disabled, which means that no information is written to the log file. To create a log file press "Win central + R" to open the Run box. Blazon "wf.msc" and press Enter. The "Windows Firewall with Advanced Security" screen appears. On the right side of the screen, click "Properties."

A new dialog box appears. At present click the "Private Profile" tab and select "Customize" in the "Logging Section."

A new window opens and from that screen choose your maximum log size, location, and whether to log only dropped packets, successful connection or both. A dropped packet is a parcel that Windows Firewall has blocked. A successful connection refers both to incoming connections likewise equally any connection you have made over the Internet, simply information technology doesn't always hateful that an intruder has successfully connected to your computer.

By default, Windows Firewall writes log entries to %SystemRoot%\System32\LogFiles\Firewall\Pfirewall.log and stores merely the last iv MB of data. In nigh production environments, this log volition constantly write to your hard disk drive, and if y'all change the size limit of the log file (to log activity over a long catamenia of time) then it may cause a performance impact. For this reason, you should enable logging only when actively troubleshooting a trouble so immediately disable logging when you're finished.

Next, click the "Public Profile" tab and repeat the same steps you did for "Private Contour" tab. You've at present turned on the log for both private and public network connections. The log file will exist created in a W3C extended log format (.log) that you tin can examine with a text editor of your choice or import them into a spreadsheet. A unmarried log file can contain thousands of text entries, and so if you are reading them through Notepad and so disable word wrapping to preserve the column formatting. If you are viewing the log file in a spreadsheet then all the fields will be logically displayed in columns for easier analysis.

On the main "Windows Firewall with Advanced Security" screen, ringlet down until you lot see the "Monitoring" link. In the Details pane, under "Logging Settings", click the file path next to "File Name." The log opens in Notepad.

Interpreting the Windows Firewall log

The Windows Firewall security log contains two sections. The header provides static, descriptive information about the version of the log, and the fields available. The trunk of the log is the compiled data that is entered as a result of traffic that tries to cross the firewall. It is a dynamic list, and new entries go on actualization at the bottom of the log. The fields are written from left to correct across the page. The (-) is used when at that place is no entry bachelor for the field.

According to the Microsoft Technet documentation the header of the log file contains:

Version — Displays which version of the Windows Firewall security log is installed.
Software — Displays the name of the software creating the log.
Fourth dimension — Indicates that all the timestamp information in the log are in local time.
Fields — Displays a list of fields that are bachelor for security log entries, if data is available.

While the torso of the log file contains:

date — The appointment field identifies the date in the format YYYY-MM-DD.
time — The local time is displayed in the log file using the format HH:MM:SS. The hours are referenced in 24-hour format.
action — Equally the firewall processes traffic, certain actions are recorded. The logged deportment are DROP for dropping a connexion, Open for opening a connection, Shut for endmost a connexion, OPEN-Entering for an inbound session opened to the local calculator, and INFO-EVENTS-LOST for events processed by the Windows Firewall, but were not recorded in the security log.
protocol — The protocol used such as TCP, UDP, or ICMP.
src-ip — Displays the source IP address (the IP address of the computer attempting to establish communication).
dst-ip — Displays the destination IP accost of a connection attempt.
src-port — The port number on the sending computer from which the connection was attempted.
dst-port — The port to which the sending computer was trying to brand a connectedness.
size — Displays the packet size in bytes.
tcpflags — Information virtually TCP command flags in TCP headers.
tcpsyn — Displays the TCP sequence number in the package.
tcpack — Displays the TCP acknowledgement number in the package.
tcpwin — Displays the TCP window size, in bytes, in the parcel.
icmptype — Information about the ICMP messages.
icmpcode — Information about the ICMP messages.
info — Displays an entry that depends on the type of action that occurred.
path — Displays the direction of the communication. The options available are SEND, RECEIVE, Forward, and UNKNOWN.

Every bit you notice, the log entry is indeed big and may have up to 17 pieces of information associated with each event. Still, but the get-go 8 pieces of information are important for general assay. With the details in your hand now you tin analyze the data for malicious action or debug awarding failures.

If you suspect any malicious activity, and then open the log file in Notepad and filter all the log entries with DROP in the action field and annotation whether the destination IP address ends with a number other than 255. If you find many such entries, then take a note of the destination IP addresses of the packets. In one case you have finished troubleshooting the problem, you can disable the firewall logging.

Troubleshooting network bug tin be quite daunting at times and a recommended proficient practice when troubleshooting Windows Firewall is to enable the native logs. Although the Windows Firewall log file is not useful for analyzing the overall security of your network, it however remains a good practice if you want to monitor what is happening behind the scenes.