Event ID 4625 Null SID Guest account currently disabled

An account failed to log on.

Subject:

Security ID: Domain\Administrator

Account Name: Administrator

Account Domain: Domain

Logon ID: 0x4DEEDAB8

Logon Type: 3

Account For Which Logon Failed:

Security ID: NULL SID

Account Name: Guest

Account Domain: Computername

Failure Information:

Failure Reason: Account currently disabled.

Status: 0xC000006E

Sub Status: 0xC0000072

Process Information:

Caller Process ID: 0x5acc

Caller Process Name: C:\Windows\explorer.exe

Network Information:

Workstation Name: Computername

Source Network Address: -

Source Port: -

Detailed Authentication Information:

Logon Process: Advapi  

Authentication Package: Negotiate

Transited Services: -

Package Name (NTLM only): -

Key Length: 0

This event is generated when a logon request fails. It is generated on the computer where access was attempted.

The Subject fields indicate the account on the local system which requested the logon. This is most commonly a service such as the Server service, or a local process such as Winlogon.exe or Services.exe.

The Logon Type field indicates the kind of logon that was requested. The most common types are 2 (interactive) and 3 (network).

The Process Information fields indicate which account and process on the system requested the logon.

The Network Information fields indicate where a remote logon request originated. Workstation name is not always available and may be left blank in some cases.

The authentication information fields provide detailed information about this specific logon request.

- Transited services indicate which intermediate services have participated in this logon request.

- Package name indicates which sub-protocol was used among the NTLM protocols.

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That must be not the remote computer attempt to logon your server, if it does and failure, the security log will log “Unknown username or bad password”.

The Network Information fields indicate where a remote logon request originated. The workstation name is not always available and may be left blank in some cases.

It's by design. The core issue for that is that Network and Sharing Center wants to know whether the guest account is enabled for network access

Solution:
Remove "Everyone" NTFS permission from the shared folder.

Reference: 

Event ID 4625 Null SID Guest account currently disabled (microsoft.com)