Ensure the iptables is initialized with your new configurations when the virtual machine reboots and not with the default setup. You can issue the following commands to save the firewall rules.

确保iptables在虚拟机重启时用新配置而不是默认设置进行初始化。

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There are the glimmers of a plan: strengthen the banks to withstand the shock of default and then build a massive firewall around Greece to avoid a domino effect.

BBC: Euro crisis: a torrent of words, but no clarity

BlackICE Defender and McAfee.com Personal Firewall have the best configuration options and default settings.

CNN: Insulate your PC from hackers

To combat this risk, European leaders have agreed a 700bn-euro firewall to protect the rest of the eurozone from a full-blown Greek default.

BBC: Eurozone crisis explained