Date: Fri, 18 Apr 2008 13:18:44 -0400 From: Jon Radel <jon@radel.com> To: Paul Schmehl <pauls@utdallas.edu> Cc: freebsd-questions@freebsd.org Subject: Re: [SSHd] Limiting access from authorized IP's Message-ID: <4808D7F4.8000709@radel.com> In-Reply-To: <1EBA9459C137D287EEE2560D@utd65257.utdallas.edu> References: <2tng04doovnmtkr7or9kfkb596fgjfoj1c@4ax.com> <20080418191449.212f43d3.gary@pattersonsoftware.com> <1EBA9459C137D287EEE2560D@utd65257.utdallas.edu>
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This is a cryptographically signed message in MIME format. --------------ms010707070104030707060202 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Paul Schmehl wrote: > I see this statement all the time, and I wonder why. What does a > firewall on an individual host accomplish? > > I have maintained publicly available servers for a small hobby domain > for almost ten years now. Initially, I bought in to this logic and ran > a firewall. (At that time we only had one server.) What it cost me was > CPU and memory. What it gained me was nothing. I turned it off. I have > never run a firewall on a publicly available host since. > > Firewalls are for preventing access to running services. By definition, > if you are running a service, you want it to be accessed. So firewalls > are self-defeating or completely useless at the host level **unless** > you don't know what you're doing. For an enterprise they make a great > deal of sense. No matter what a user inside your network might do, you > can prevent access by simply not allowing traffic on that port. Yes, in a world where nothing ever breaks, all system administrators never make dumb mistakes, and no one ever breaks into your box to install services that you certainly wouldn't approve of, the defense-in-depth techniques being discussed here are pretty much a waste of time. Alas, alack, my machines prove every couple of years that they don't live in such a world. Must be me. ;-) > If *everyone* knew how to properly configure and maintain a host, even > enterprise firewalls would be completely unnecessary. And if you've got users on your network.... Oh, my, users do the darnedest things. As one little example: My firewall blocks outbound traffic to port 25 from all those pesky workstations to anywhere other than the local SMTP servers. Why? Makes me worry just a bit less about some Windows box pumping spam out to the world due to an unfortunate choice made by a user. I doubt there's an enterprise in the world where every user both knows enough about host security *and* is disciplined enough to apply that knowledge every minute of every day. But then, I'm the guy who takes the time to put on his seatbelt each and every time he starts the car, despite never, not once, having to actually use it in 3 decades of driving. > Firewalls are too often crutches for people that don't want to learn > how to properly maintain a host. Now that, on the other hand, I can completely agree with. --Jon Radel --------------ms010707070104030707060202 Content-Type: application/x-pkcs7-signature; name="smime.p7s" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="smime.p7s" Content-Description: S/MIME Cryptographic Signature MIAGCSqGSIb3DQEHAqCAMIACAQExCzAJBgUrDgMCGgUAMIAGCSqGSIb3DQEHAQAAoIIJMTCC AvMwggJcoAMCAQICEG2TkfF/93Sx9LCftry1D3YwDQYJKoZIhvcNAQEFBQAwYjELMAkGA1UE BhMCWkExJTAjBgNVBAoTHFRoYXd0ZSBDb25zdWx0aW5nIChQdHkpIEx0ZC4xLDAqBgNVBAMT I1RoYXd0ZSBQZXJzb25hbCBGcmVlbWFpbCBJc3N1aW5nIENBMB4XDTA4MDMyNDE2NTkyMVoX DTA5MDMyNDE2NTkyMVowXjEOMAwGA1UEBBMFUmFkZWwxEzARBgNVBCoTCkpvbiBUaG9tYXMx GTAXBgNVBAMTEEpvbiBUaG9tYXMgUmFkZWwxHDAaBgkqhkiG9w0BCQEWDWpvbkByYWRlbC5j b20wggEiMA0GCSqGSIb3DQEBAQUAA4IBDwAwggEKAoIBAQDPdCxQufreHHDAI9YN2axx87Rf 0TK1PYFMlJHi4y1ebdAMPqR6M44bz+3m8YnKn1bmIf7dWyisWyAIQYCOhW/2r66o4MdF9qJ9 z5uhMy+28zaJP/Glg64C3WPM0VfveCgvu+ApEyf2JDbjc/hUomw8KpppgOcn1wX6PZGbhHVv eAvDTWJ0ugqo08Ny6GR0bsGvePmxdWSQq+0aGTHqA1I2EozJBZ8W5xlUtKe22j56i1Uw1ujk Rlosdu2PTs8QOY1OUHuLPnEV9EWtYF7g6bXDUDsJxypXZy9qTipPplYXjdWgkLVRvezri+BN kgin8UKhKLQ99vS25zrMFKu80g31AgMBAAGjKjAoMBgGA1UdEQQRMA+BDWpvbkByYWRlbC5j b20wDAYDVR0TAQH/BAIwADANBgkqhkiG9w0BAQUFAAOBgQAR4u9o4CFvztyo0sZb3tCQIWYb 5U4jW9da3goVwWIkMz+qeCb2kiTQfsSmOdF9YJ8VTRdYW0l0fQbqL5JikVhaYeX85cpqZ3iA /PPJpfPtJw8g5jJOAROVAvxydMZXQYxyIBMV4HNG3qir44YnyfmJXkBtRFYWdxBc7bQpoZSZ jzCCAvMwggJcoAMCAQICEG2TkfF/93Sx9LCftry1D3YwDQYJKoZIhvcNAQEFBQAwYjELMAkG A1UEBhMCWkExJTAjBgNVBAoTHFRoYXd0ZSBDb25zdWx0aW5nIChQdHkpIEx0ZC4xLDAqBgNV BAMTI1RoYXd0ZSBQZXJzb25hbCBGcmVlbWFpbCBJc3N1aW5nIENBMB4XDTA4MDMyNDE2NTky MVoXDTA5MDMyNDE2NTkyMVowXjEOMAwGA1UEBBMFUmFkZWwxEzARBgNVBCoTCkpvbiBUaG9t YXMxGTAXBgNVBAMTEEpvbiBUaG9tYXMgUmFkZWwxHDAaBgkqhkiG9w0BCQEWDWpvbkByYWRl bC5jb20wggEiMA0GCSqGSIb3DQEBAQUAA4IBDwAwggEKAoIBAQDPdCxQufreHHDAI9YN2axx 87Rf0TK1PYFMlJHi4y1ebdAMPqR6M44bz+3m8YnKn1bmIf7dWyisWyAIQYCOhW/2r66o4MdF 9qJ9z5uhMy+28zaJP/Glg64C3WPM0VfveCgvu+ApEyf2JDbjc/hUomw8KpppgOcn1wX6PZGb hHVveAvDTWJ0ugqo08Ny6GR0bsGvePmxdWSQq+0aGTHqA1I2EozJBZ8W5xlUtKe22j56i1Uw 1ujkRlosdu2PTs8QOY1OUHuLPnEV9EWtYF7g6bXDUDsJxypXZy9qTipPplYXjdWgkLVRvezr i+BNkgin8UKhKLQ99vS25zrMFKu80g31AgMBAAGjKjAoMBgGA1UdEQQRMA+BDWpvbkByYWRl bC5jb20wDAYDVR0TAQH/BAIwADANBgkqhkiG9w0BAQUFAAOBgQAR4u9o4CFvztyo0sZb3tCQ IWYb5U4jW9da3goVwWIkMz+qeCb2kiTQfsSmOdF9YJ8VTRdYW0l0fQbqL5JikVhaYeX85cpq Z3iA/PPJpfPtJw8g5jJOAROVAvxydMZXQYxyIBMV4HNG3qir44YnyfmJXkBtRFYWdxBc7bQp oZSZjzCCAz8wggKooAMCAQICAQ0wDQYJKoZIhvcNAQEFBQAwgdExCzAJBgNVBAYTAlpBMRUw EwYDVQQIEwxXZXN0ZXJuIENhcGUxEjAQBgNVBAcTCUNhcGUgVG93bjEaMBgGA1UEChMRVGhh d3RlIENvbnN1bHRpbmcxKDAmBgNVBAsTH0NlcnRpZmljYXRpb24gU2VydmljZXMgRGl2aXNp b24xJDAiBgNVBAMTG1RoYXd0ZSBQZXJzb25hbCBGcmVlbWFpbCBDQTErMCkGCSqGSIb3DQEJ ARYccGVyc29uYWwtZnJlZW1haWxAdGhhd3RlLmNvbTAeFw0wMzA3MTcwMDAwMDBaFw0xMzA3 MTYyMzU5NTlaMGIxCzAJBgNVBAYTAlpBMSUwIwYDVQQKExxUaGF3dGUgQ29uc3VsdGluZyAo UHR5KSBMdGQuMSwwKgYDVQQDEyNUaGF3dGUgUGVyc29uYWwgRnJlZW1haWwgSXNzdWluZyBD QTCBnzANBgkqhkiG9w0BAQEFAAOBjQAwgYkCgYEAxKY8VXNV+065yplaHmjAdQRwnd/p/6Me 7L3N9VvyGna9fww6YfK/Uc4B1OVQCjDXAmNaLIkVcI7dyfArhVqqP3FWy688Cwfn8R+RNiQq E88r1fOCdz0Dviv+uxg+B79AgAJk16emu59l0cUqVIUPSAR/p7bRPGEEQB5kGXJgt/sCAwEA AaOBlDCBkTASBgNVHRMBAf8ECDAGAQH/AgEAMEMGA1UdHwQ8MDowOKA2oDSGMmh0dHA6Ly9j cmwudGhhd3RlLmNvbS9UaGF3dGVQZXJzb25hbEZyZWVtYWlsQ0EuY3JsMAsGA1UdDwQEAwIB BjApBgNVHREEIjAgpB4wHDEaMBgGA1UEAxMRUHJpdmF0ZUxhYmVsMi0xMzgwDQYJKoZIhvcN AQEFBQADgYEASIzRUIPqCy7MDaNmrGcPf6+svsIXoUOWlJ1/TCG4+DYfqi2fNi/A9BxQIJNw PP2t4WFiw9k6GX6EsZkbAMUaC4J0niVQlGLH2ydxVyWN3amcOY6MIE9lX5Xa9/eH1sYITq72 6jTlEBpbNU1341YheILcIRk13iSx0x1G/11fZU8xggNkMIIDYAIBATB2MGIxCzAJBgNVBAYT AlpBMSUwIwYDVQQKExxUaGF3dGUgQ29uc3VsdGluZyAoUHR5KSBMdGQuMSwwKgYDVQQDEyNU aGF3dGUgUGVyc29uYWwgRnJlZW1haWwgSXNzdWluZyBDQQIQbZOR8X/3dLH0sJ+2vLUPdjAJ BgUrDgMCGgUAoIIBwzAYBgkqhkiG9w0BCQMxCwYJKoZIhvcNAQcBMBwGCSqGSIb3DQEJBTEP Fw0wODA0MTgxNzE4NDRaMCMGCSqGSIb3DQEJBDEWBBRzoFaUhxUaIoZQ6Pn2bjays9yCZTBS BgkqhkiG9w0BCQ8xRTBDMAoGCCqGSIb3DQMHMA4GCCqGSIb3DQMCAgIAgDANBggqhkiG9w0D AgIBQDAHBgUrDgMCBzANBggqhkiG9w0DAgIBKDCBhQYJKwYBBAGCNxAEMXgwdjBiMQswCQYD VQQGEwJaQTElMCMGA1UEChMcVGhhd3RlIENvbnN1bHRpbmcgKFB0eSkgTHRkLjEsMCoGA1UE AxMjVGhhd3RlIFBlcnNvbmFsIEZyZWVtYWlsIElzc3VpbmcgQ0ECEG2TkfF/93Sx9LCftry1 D3YwgYcGCyqGSIb3DQEJEAILMXigdjBiMQswCQYDVQQGEwJaQTElMCMGA1UEChMcVGhhd3Rl IENvbnN1bHRpbmcgKFB0eSkgTHRkLjEsMCoGA1UEAxMjVGhhd3RlIFBlcnNvbmFsIEZyZWVt YWlsIElzc3VpbmcgQ0ECEG2TkfF/93Sx9LCftry1D3YwDQYJKoZIhvcNAQEBBQAEggEAQkus cpeMhICrLW1IBUuUCyow9yFf0IfI7V7/mZyXebD2y+07cZ4jGnOHCt3969FMNFAoaU5cllEC 1MJFLGvU1dXUFCQF0IHPxMbASQa/AnIFJZywOZWVfQwLkgBDzplHBsPKNyqHCWjqkYUtUGsx GFVsXFHbtMO9exPPuKaTGstW8cAbifdh7uvBRZQwkK28NXjrss+xSJTASfFmAHNFHp5Rz4nq tEVm+XTpH/Wywy8Z9gJZl+83n3p8DND0jPn1X2pkb1h3jpCO3RptXgQ4r78B88+AdUC2Puzv N/VmSZNsPpV8MQUjjrDFknGpNDmLgfrBslL/juJiag1c7cSu3QAAAAAAAA== --------------ms010707070104030707060202--
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