Asterisk eats all CPU
From Kolmisoft Wiki
Network problem
Change to correct ip in /etc/asterisk/h323.conf, restart Asterisk
DDOS attack
Unload chan_sip.so module. If it helps - proceed.
Check sip debug. If a lot of packets come from one IP - block it.
Check if it helps.
Broken code
Check with: http://www.moythreads.com/wordpress/2009/05/06/why-does-asterisk-consume-100-cpu/
Investigate the module which causes it.
If not critical (like IAX2) -> unload it and check if it helps. Rinse and repeat if not.