you can use cron or the at command on IX flavored systems for "timing"
SNMPD is designed for monitoring systems. Is also installed on IXs by default and sometimes fault on Windows. Loads of good...

disconnect/disallow the offending systems asap

this will reduce load and buy time for research & fixing.

www.symantec.com is reporting some new worms.. you might wanna hit the site..
there...