I'm running nginx wordpress server in KVM using 12.04 server x86. It was running very well about 4 month until 2 hours ago. I found that my website is down and no ping response. Virt-manager logged high cpu load(plz see the picture below) before unexpected shut down. I want to know what process caused unexpected shutdown. The following log files make me think my server is attacked. Any suggestions and help would be appreciated.

kern.log and syslog showed me same output.

Nov 11 03:54:11 www kernel: [1344541.156239] [UFW BLOCK] IN=eth0 OUT= MAC= SRC=0.0.0.0 DST=224.0. 0.1 LEN=32 TOS=0x00 PREC=0xC0 TTL=1 ID=0 DF PROTO=2

Nov 11 03:54:11 www kernel: [1344541.156315] [UFW BLOCK] IN=eth0 OUT= MAC= SRC=0101:080a:2334:c90 0:0100:0000:0000:0000 DST=ff02:0000:0000:0000:0000:0000:0000:0001 LEN=72 TC=0 HOPLIMIT=1 FLOWLBL=0 PROTO=ICMPv6 TYPE=130 CODE=0

/nginx/access.log showed me

119.235.237.17 - - [11/Nov/2012:03:45:29 +0900] "GET /blog HTTP/1.1" 200 30493 "-" "Yeti/1.0 (NHN Corp.; http://help.naver.com/robots/)" my-server-ip - - [11/Nov/2012:11:05:30 +0900] "POST /wp-cron.php?doing_wp_cron=13 HTTP/1.0" 499 0 "-" "WordPress/3.4.2; http://mywebsite.com"

Server turned on in here. 119.235.237.16 - - [11/Nov/2012:11:05:30 +0900] "GET /blog HTTP/1.1" 200 32935 "-" "Yeti/1.0 (NHN Corp.; http://help.naver.com/robots/)"