7.9 Ensure RC4 Cipher Suites is Disabled - RC4 56/128

Information

The RC4 Cipher Suites are considered insecure, therefore should be disabled.

Note: RC4 cipher enabled by default on Server 2012 and 2012 R2 is RC4 128/128.

Rationale:

The use of RC4 may increase an adversaries ability to read sensitive information sent over SSL/TLS.

Impact:

The RC4 Cipher Suites will not be available.

Solution

Perform the following to disable RC4 40/128, RC4 56/128, RC4 64/128, RC4 128/128 ciphers:

Set the following Registry keys to 0.

HKLM\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Ciphers\RC4 40/128:Enabled
HKLM\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Ciphers\RC4 56/128:Enabled
HKLM\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Ciphers\RC4 64/128:Enabled
HKLM\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Ciphers\RC4 128/128:Enabled

To disable using PowerShell enter the following commands:

(Get-Item 'HKLM:\').OpenSubKey('SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Ciphers', $true).CreateSubKey('RC4 40/128')

New-ItemProperty -path 'HKLM:\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Ciphers\RC4 40/128' -name 'Enabled' -value '0' -PropertyType 'DWord' -Force | Out-Null

(Get-Item 'HKLM:\').OpenSubKey('SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Ciphers', $true).CreateSubKey('RC4 56/128')

New-ItemProperty -path 'HKLM:\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Ciphers\RC4 56/128' -name 'Enabled' -value '0' -PropertyType 'DWord' -Force | Out-Null

(Get-Item 'HKLM:\').OpenSubKey('SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Ciphers', $true).CreateSubKey('RC4 64/128')

New-ItemProperty -path 'HKLM:\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Ciphers\RC4 64/128' -name 'Enabled' -value '0' -PropertyType 'DWord' -Force | Out-Null

(Get-Item 'HKLM:\').OpenSubKey('SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Ciphers', $true).CreateSubKey('RC4 128/128')

New-ItemProperty -path 'HKLM:\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Ciphers\RC4 128/128' -name 'Enabled' -value '0' -PropertyType 'DWord' -Force | Out-Null

See Also

https://workbench.cisecurity.org/files/4131