SMB sharing not accessible when TCP port 445 listening in Windows Server - Windows Server (2024)

This article provides a solution to an issue where you can't access a Server Message Block (SMB) shared resource even when the shared resource is enabled in the target Windows Server.

Original KB number: 4471134

Symptoms

You can't access a Server Message Block (SMB) shared resource even when the shared resource is enabled on the target Windows Server. When you run the netstat command to show the network connections, the results show that TCP port 445 is listening. However, network traces show that communication on TCP port 445 is failing as follows:

After you enable the auditing of Filtering Platform Policy Change events by using the following command, you may experience some events (such as event ID 5152) that indicate blocking.

auditpol /set /subcategory:"Filtering Platform Packet Drop" /success:enable /failure:enable

Example of event ID 5152:

Cause

This issue occurs because the Adylkuzz malware that leverages the same SMBv1 vulnerability as Wannacrypt adds an IPSec policy that's named NETBC that blocks incoming traffic on the SMB server that's using TCP port 445. Some Adylkuzz-cleanup tools can remove the malware but fail to delete the IPSec policy. For details, see Win32/Adylkuzz.B.

Resolution

To fix this issue, follow these steps:

1. Install the security update MS17-010 version appropriate to the operating system.

2. Follow the steps on the "What to do now tab" of Win32/Adylkuzz.B.

3. Run a scan by using the Microsoft Security Scanner.

   See Also

   About the SMBv1 retirement

4. Check whether the IPSec policy blocks the TCP port 445 by using the following commands (and see the cited results for examples).

   netsh ipsec static show policy all

   Policy Name: netbc Description: NONE Last Modified: <DateTime> Assigned: YES Master PFS: NO Polling Interval: 180 minutes

   netsh ipsec static show filterlist all level=verbose

   FilterList Name: block Description: NONE Store: Local Store <WIN> Last Modified: <DateTime> GUID: {ID} No. of Filters: 1 Filter(s) --------- Description: 445 Mirrored: YES Source IP Address: <IP Address> Source Mask: 0.0.0.0 Source DNS Name: <IP Address> Destination IP Address: <IP Address> Destination DNS Name: <IP Address> Protocol: TCP Source Port: ANY Destination Port : 445 

   Note

   When you run the commands on an uninfected server, there is no policy.

5. If the IPSec policy exists, delete it by using one of the following methods.

   • Run the following command:

     netsh ipsec static delete policy name=netbc

   • Use Group Policy Editor (GPEdit.msc):

     Local Group Policy Editor/Computer Configuration/Windows Settings/Security Settings/IPSec Security

More information

Since October 2016, Microsoft has been using a new servicing model for the supported versions of Windows Server updates. This new servicing model for distributing updates simplifies the way that security and reliability issues are addressed. Microsoft recommends keeping your systems up-to-date to make sure that they are protected and have the latest fixes applied.

This threat can run the following commands:

netsh ipsec static add policy name=netbcnetsh ipsec static add filterlist name=blocknetsh ipsec static add filteraction name=block action=blocknetsh ipsec static add filter filterlist=block any srcmask=32 srcport=0 dstaddr=me dstport=445 protocol=tcp description=445netsh ipsec static add rule name=block policy=netbc filterlist=block filteraction=blocknetsh ipsec static set policy name=netbc assign=y

It can also add firewall rules to allow connections by using these commands:

netsh advfirewall firewall add rule name="Chrome" dir=in program="C:\Program Files (x86)\Google\Chrome\Application\chrome.txt" action=allownetsh advfirewall firewall add rule name="Windriver" dir=in program="C:\Program Files (x86)\Hardware Driver Management\windriver.exe" action=allow