# System.Security.Authentication

``` diff
 namespace System.Security.Authentication {
     [FlagsAttribute]
     public enum SslProtocols {
-        Tls = 192,
+        [ObsoleteAttribute("TLS versions 1.0 and 1.1 have known vulnerabilities and are not recommended. Use a newer TLS version instead, or use SslProtocols.None to defer to OS defaults.", DiagnosticId="SYSLIB0039", UrlFormat="https://aka.ms/dotnet-warnings/{0}")]
+        Tls = 192,
-        Tls11 = 768,
+        [ObsoleteAttribute("TLS versions 1.0 and 1.1 have known vulnerabilities and are not recommended. Use a newer TLS version instead, or use SslProtocols.None to defer to OS defaults.", DiagnosticId="SYSLIB0039", UrlFormat="https://aka.ms/dotnet-warnings/{0}")]
+        Tls11 = 768,
     }
 }
```

