"SMB: User Password Brute Force Attempt detected" on share that is not being accessed

[Indorama_Ventures]

Recently I accessed a SMB share on a corporate Synology device (through the PA firewall). Accessing this share is hardly ever used. Now...days later, after several reboots of the client computer, the Firewall keeps on detecting the "vulnerability" SMB: User Password Brute Force Attempt(40004)

This is something I cannot explain. There are no active connections to this share from the client computer. There is nothing in the credential manager of Windows. There is nothing it the frequently accessed locations... Any idea why the Palo Alto would think this vulnerability is triggered an how can I find the "culprit" program which tries to access this file share?

Remko

[SutareMayur]

It seems there are still login attempts from client which is triggering child signature. Are you seeing same client IP every time?

[Indorama_Ventures]

Yes, according to the firewall it is the same client (IP address). 

Unfortunately I can determine what is causing the SMB traffic. There is simply nothing open on the client. 

Every 2 hours or so I see a whole bunch of warnings appear in the logs of the firewall. Then it is silent again after which the process repeats itself.

Very weird ?!?!?

Remko

[SutareMayur · Accepted solution]

Try by running wireshark on client end to check if there are any hits to server.

[ZS_NET]

yes, this can be a way to cross verify it.

[Indorama_Ventures]

Good tip... Will do!

[Indorama_Ventures]

Wireshark reveiled that it was a webservice that tried to contact the Synology. From there, I guess it tried to open the SMB share on the computer. 

Although not visible on the computer itself it was a browser session on tcp/5000 which initiated the connection.