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On Sun, Oct 05, 2003 at 12:59:30PM +0200 or thereabouts, Nick Van Vlaenderen wrote: |
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> I was wondering how I could hide my uptime and OS for portscans. If |
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> someone scans my server (for example using Nmap), he can see what OS I am |
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> running and what the uptime of the box is. Does anyone know which firewall |
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> rule I need to prevent this? And how does Nmap collect this information? |
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> Is it related to what services there are running on the server? |
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The nmap freak patch will prevent accurate OS fingerprinting: |
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http://packetstormsecurity.nl/UNIX/patches/nmap-freak-patch |
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it's also part of wolk-sources in portage. |
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As for uptime measurements, that relies on the TCP timestamp option. IIRC, |
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there's an option in grsecurity to disable or munge that. grsec is also |
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part of wolk-sources and is available as a separate patch here: |
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http://www.grsecurity.net/ |
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I believe grsec also has facilities to confuse OS fingerprinting attempts |
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as well. |
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--kurt |
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