Detectionlowtest
MaxMpxCt Registry Value Changed
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.
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Launch
Nasreddine Bencherchali (Nextron Systems)Created Tue Mar 190e6a9e62-627e-496c-aef5-bfa39da29b5ewindows
Log Source
WindowsRegistry Set
ProductWindows← raw: windows
CategoryRegistry Set← raw: registry_set
Detection Logic
Detection Logic1 selector
detection:
selection:
TargetObject|endswith: '\Services\LanmanServer\Parameters\MaxMpxCt'
condition: selectionFalse Positives
Unknown
False positive likelihood has not been assessed. Additional context may be needed during triage.
MITRE ATT&CK
Tactics
Sub-techniques
Rule Metadata
Rule ID
0e6a9e62-627e-496c-aef5-bfa39da29b5e
Status
test
Level
low
Type
Detection
Created
Tue Mar 19
Path
rules/windows/registry/registry_set/registry_set_optimize_file_sharing_network.yml
Raw Tags
attack.defense-evasionattack.t1070.005