My asterisk server always have a large CPU usage process

i have a Centos 5 server which hosted asterisk 13. server works fine last week but now top command always show me a process with large amount of CPU usage. when i kill the process a few second later another command with large CPU usage started. many times processes command is “.syslog” but have other command like “qjennjifes”, “vnvebynufu” and another unknown commands like that.

It looks like someone has hacked you.
Moreover, CentOS 5 has been end-of-life for almost a year.

I recommend you reinstalling Asterisk on a clean CentOS 6.