topic Re: "SMB: User Password Brute Force Attempt detected" on share that is not being accessed in General Topics

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

Indorama_Ventures — Thu, 06 Feb 2020 07:58:41 GMT

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

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

SutareMayur — Thu, 06 Feb 2020 13:42:33 GMT

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

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

Indorama_Ventures — Thu, 06 Feb 2020 14:09:52 GMT

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

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

SutareMayur — Thu, 06 Feb 2020 14:29:15 GMT

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

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

ZS_NET — Thu, 06 Feb 2020 14:32:16 GMT

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

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

Indorama_Ventures — Thu, 06 Feb 2020 14:34:05 GMT

Good tip... Will do!

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

Indorama_Ventures — Thu, 13 Feb 2020 09:33:42 GMT

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.

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

uduwawalan — Wed, 11 Jun 2025 08:14:12 GMT

We are in the process of implementing zero trust via Palo and now we are seeing this. No one has even logged in to the machine at the time the alerts are raised.. The machines certainly don't have any malicious software on them and we have a xdr product protecting them and the xdr product is not raising the alarm. It's difficult to do a packet capture as the alerts are raised at random times.