A PC connected to the internet is only as secure as it's firewall. EchoLink or not, if you're not running a firewall, you could be in for a lot of trouble. I have nothing but good things to say about ZoneAlarm(http://www.zonealarm.com
). There is a free version that you can download from their site. Virus protection software is also a must these days.
My EchoLink station is running on its own, dedicated PC. Nothing is installed except Win98SE and EchoLink (along with firewall and virus protection). If a hacker gets in, he won't get much.
Hope this helps!
Bill - KB3GUN
EchoLink Node 23115
EchoLink Forums: http://www.swronline.com