A successful DoS attack overwhelms its victim with such a massive barrage of false

In addition to limiting the number of concurrent sessions from the same source IP
address, you can also limit the number of concurrent sessions to the same
destination IP address. One benefit of setting a source-based session limit is that it
can stem an attack such as the Nimda virus (which is actually both a virus and a
worm) that infects a server and then begins generating massive amounts of traffic
from that server. Because all the virus-generated traffic originates from the same IP
address, a source-based session limit ensures that the firewall can curb such
excessive amounts of traffic.