TMA-IIS-7.7
Ensure NULL Cipher Suites is Disabled
HighLevel 1Automatediis
Description
The NULL cipher does not provide data confidentiality or integrity, therefore it is recommended that the NULL cipher be disabled. SCHANNEL\Ciphers\NULL must exist with Enabled=0 (read via the .NET registry API because the key names contain "/"). PowerShell 5.1; reads the registry (run elevated).
How it is checked
Audit method: Windows registry
registry
$c = 'SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Ciphers'; function Get-Cipher($n) { $k = [Microsoft.Win32.Registry]::LocalMachine.OpenSubKey("$c\$n"); $v = $null; if ($k) { $v = $k.GetValue('Enabled'); $k.Close() }; $v }; $bad = @('NULL' | Where-Object { $v = Get-Cipher $_; $null -eq $v -or [long]$v -ne 0 }); if ($bad.Count -eq 0) { 'compliant' } else { 'noncompliant' }- Expected output
compliant
How it is fixed
Fix method: Guidance or infrastructure patch
([Microsoft.Win32.Registry]::LocalMachine.CreateSubKey('SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Ciphers\NULL')).SetValue('Enabled', 0, 'DWord') for each listed cipher (PowerShell drive paths cannot contain '/'), then reboot.
Properties
- Operating systems
- Any
- Tags
- iistls
- Reference
- CIS Microsoft IIS 10 Benchmark v1.2.1 - 7.7 Ensure NULL Cipher Suites is Disabled
Check this host
Run this on a machine you are allowed to audit. The scan is read-only.
shell
tmaegis scan --target iis