you can change your INPUT policy from REJECT to DROP like:
Code:
iptables -P INPUT DROP
keep in mind that you might instead be filtering with a REJECT rule (instead of a policy), and in such a case you'd need to change the rule, or get rid of it and use the policy... having said that, are you sure this is what they mean with
counter-probes?? cuz the way they write it it sounds like your box did a port scan of theirs or something... anyhow, just wondering...