Microsoft ha disminuido el número máximo de conexiones por segundo en Windows XP SP2 para reducir la velocidad de propagación de gusanos como sasser. El efecto de esta medida también lo notan aplicaciones como Emule que ven reducido su redimiento ante la imposibilidad de usar más conexiones.
"Thanks very much for responding. This new feature is one of the stack's "springboards", security features designed to proactively reduce the future threat from attacks like blaster and Sasser that typically spread by opening connections to random addresses. In fact, if this feature had already been deployed, Sasser would have taken much longer to spread.
It's not likely to help stop the spread of spam unless spammers are trying to reach open email relays in the same way, by opening connections on smtp ports of random IP addresses. This is new with XP SP2 and we're trying to get it right so that it does not interfere with normal system operation or performance of normal, legitimate applications, but does slow the spread of viral code. New connection attempts over the limit for half-open connections get queued and worked off at a certain (limited rate)."