If you have not patched your esx/esxi, do it!
Patch overview : http://www.vmware.com/security/advisories/VMSA-2011-0007.html
ESX3.5 and ESX3.03 are safe.
Patch can be obtained here: (ESXi410-201104001 )
Unzip it and copy files to your esxi box(you should have embeddedEsx directory after unpacking)
esxupdate -m metadata.zip update
Make sure that host is in Maintenance mode, and machines are powered off, or migrated to other host in cluster if you have one. After installing all patches reboot your host.
After reboot check if patches were installed by typing:
http://www.vmware.com/pdf/vsphere4/r41/vsp_41_esxupdate.pdf -> you can read vmware manual regarding updating your host
http://www.vmware.com/support/developer/vcli/vcli41/doc/reference/vihostupdate.html -> here is short manual for vihostupdate if you want to upgrade it using rcli like vMA