<a href="http:&#x2F;&#x2F;lcamtuf.coredump.cx&#x2F;oldtcp&#x2F;tcpseq.html" rel="nofollow">http:&#x2F;&#x2F;lcamtuf.coredump.cx&#x2F;oldtcp&#x2F;tcpseq.html</a><p>&gt; However, guessing the right ISN from the entire 32-bit space (4,294,967,296 possibilities) is not feasible due to the excessive amount of bandwidth and time required. That is why a good TCP sequence number generator implementation currently provides enough security to protect against spoofing attacks, at least for the present time and in typical conditions. But increasing bandwidth and processor speed will eventually make brute force guessing of 32-bit ISNs feasible for the average attacker.<p>See also 
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