This is caused by a known bug in older Cisco versions - https://quickview.cloudapps.cisco.com/quickview/bug/CSCsy76185.
you should try upgrading your router firmware if it bothers you.
Hey,
you can create an ACL that blocks ssh traffic, and the apply it to your outbound interface:
# ip access-list extended BLOCK_SSH
# deny tcp any any eq 22
# permit ip any any
and then apply it to specific interface with:
# interface GigabitEthe...
