Windows Admin Shares
Windows systems have hidden network shares that are accessible only to administrators and provide the ability for remote file copy and other administrative functions. Example network shares include
Adversaries may use this technique in conjunction with administrator-level Valid Accounts to remotely access a networked system over server message block (SMB)  to interact with systems using remote procedure calls (RPCs),  transfer files, and run transferred binaries through remote Execution. Example execution techniques that rely on authenticated sessions over SMB/RPC are Scheduled Task, Service Execution, and Windows Management Instrumentation. Adversaries can also use NTLM hashes to access administrator shares on systems with Pass the Hash and certain configuration and patch levels. 
Adversaries can instruct Duqu to spread laterally by copying itself to shares it has enumerated and for which it has obtained legitimate credentials (via keylogging or other means). The remote host is then infected by using the compromised credentials to schedule a task on remote machines that executes the malware.
Do not reuse local administrator account passwords across systems. Ensure password complexity and uniqueness such that the passwords cannot be cracked or guessed. Deny remote use of local admin credentials to log into systems. Do not allow domain user accounts to be in the local Administrators group multiple systems.
Identify unnecessary system utilities or potentially malicious software that may be used to leverage SMB and the Windows admin shares, and audit and/or block them by using whitelisting  tools, like AppLocker,   or Software Restriction Policies  where appropriate. 
Ensure that proper logging of accounts used to log into systems is turned on and centrally collected. Windows logging is able to collect success/failure for accounts that may be used to move laterally and can be collected using tools such as Windows Event Forwarding.   Monitor remote login events and associated SMB activity for file transfers and remote process execution. Monitor the actions of remote users who connect to administrative shares. Monitor for use of tools and commands to connect to remote shares, such as Net, on the command-line interface and Discovery techniques that could be used to find remotely accessible systems.
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