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Difference between revisions of "Syn-Cookies"
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| − | Syn-cookies | + | Syn-cookies is a counter-measure against SYN flood attacks (see: [[DDoS_Attacks#Three_way_handshake_and_Connect_State|three-way tcp handshake]]) that enables resilience against these by storing the necessary state informations of the 3-way-handshake into some TCP headers (the Options and Timestamp headers) instead of keeping it in the server's RAM. Since it is a hack over TCP, Syn-cookies are usually automatically enabled during SYN-flood attacks by the operating system's network stack. |
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| + | To disable them on Linux, set net.ipv4.tcp_syncookies to 0 (or write 0 into /proc/sys/net/ipv4/tcp_syncookies) | ||
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| + | Syn-Cookies protect servers from basic SYN flood attacks quite well. | ||
Latest revision as of 16:07, 28 September 2012
Syn-cookies is a counter-measure against SYN flood attacks (see: three-way tcp handshake) that enables resilience against these by storing the necessary state informations of the 3-way-handshake into some TCP headers (the Options and Timestamp headers) instead of keeping it in the server's RAM. Since it is a hack over TCP, Syn-cookies are usually automatically enabled during SYN-flood attacks by the operating system's network stack.
To disable them on Linux, set net.ipv4.tcp_syncookies to 0 (or write 0 into /proc/sys/net/ipv4/tcp_syncookies)
Syn-Cookies protect servers from basic SYN flood attacks quite well.
