[syslog-ng]Most efficient way of "dropping" garbage ?

[Rich Armstrong]

We have a syslog-ng server, with many clients. 
One of these clients is suffering from DoS attacks. 
Since these are being logged, the syslog-ng server is also suffering !

I have created the following, temporarily :-

destination d_null { file("/dev/null"); };
filter f_null { host("dummy.name.host.net"); };
log { source(net); filter(f_null); destination(d_null); flags(final); };

This solves the problem with disk usage, but there is still some significant CPU load. 
So, the question is, "Is there a more efficient method of ignoring/dropping messages ?"

Should I be using pipe(), instead of file() ?
 
-- 
Richard Armstrong