MaxMpxCt Registry Value Changed
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About the rule
Rule Type
Standard
Rule Description
Detects changes to the "MaxMpxCt" registry value. MaxMpxCt specifies the maximum outstanding network requests for the server per client, which is used when negotiating a Server Message Block (SMB) connection with a client. Note if the value is set beyond 125 older Windows 9x clients will fail to negotiate. Ransomware threat actors and operators (specifically BlackCat) were seen increasing this value in order to handle a higher volume of traffic.
Severity
Attention
Rule Requirement
Criteria
Action1: actionname = "Registry value modified" AND OBJECTNAME endswith "\Services\LanmanServer\Parameters\MaxMpxCt" OR (OBJECTNAME endswith "\Services\LanmanServer\Parameters" AND OBJECTVALUENAME = "MaxMpxCt") select Action1.HOSTNAME,Action1.MESSAGE,Action1.OBJECTNAME,Action1.PROCESSNAME,Action1.PREVVAL,Action1.CHANGES
Detection
Execution Mode
realtime
Log Sources
Windows
Author
Nasreddine Bencherchali (Nextron Systems)
