Turn off SSH if you're not going to use it. Also traffic is being sniffed more than a school girl in Japan. Don't log on to anything, general browsing should be fine as long as nobody does a redirect and exploits you from there.
Disable IM status and any mail/calendar/contacts syncing . Or make sure they use SSL/....
As root. Turn off sshd: Code: stop sshd As root. Turn on sshd: Code: start sshd
stop sshd
start sshd
Use iptables/ip6tables to drop all incoming and outgoing connections over your wifi adapter, only allowing traffic out to your VPN/SSH tunnel server. And use that tunnel for everything. Otherwise, don't use open wifi, use your 3G internet instead.
There are known exploits for older version of OpenSSH which don't require username/password knowledge. Basically, since the software running inside N900 is relatively old and therefore very well known to the attackers, you may have additional holes. Don't accept any new certificates within browser, chat application or mail client.
Using passwords sucks big time. To prevent against a scripted password-guessing bot, just disable password login on your N900 and only use keys. edit (as root) /etc/ssh/sshd_config: Code: PasswordAuthentication no UsePAM no To use key based authentication: http://www.google.com/search?q=ssh+login+no+password
PasswordAuthentication no UsePAM no